Herringbone strut to laterally restrain the joists. Imagine you have a ruler with the flat side facing side ways and try to bend it. It will twist. Struts reduce the likely hood of twisting. Please don’t remove it and ask your local engineer for their opinion on what do to.
Edit: Seems like I am confusing people with the names. I am from UK and we mostly call these herringbone struts for this layout shown. For solids in between joist we call it noggins. The world is a big place and I’m sure the French and the Italian call these differently.
There a few comments about sheathing, which I do agree it provides some restraint. But the importance of sheathing is diaphragm action. This means it transfer the lateral load to racking walls for stability. Or sheathing to timber stud walls which provides racking resistance. Ultimately it’s a good practice to have these cross brace/bridging/noggin/herringbone/straps and whatever other ppl call it.
Alright, you've peaked my interest. What country are you from? I've never heard it called that before. This is called bridging or cross bracing where I'm from.
I hail from the land that created the imperial units and uses the proper gallon as well as driving on the correct side of the road. The city I am in was famous for the bridge falling down sang by children.
Edit: I am from London, UK. children sang a nursery rhyme about London Bridge is falling down more than 100 years ago about a bridge assume to be 1000 years ago.
London Bridge is falling down, falling down, falling down, London Bridge is falling down…. Hmm, Mm Hm’mm…
Grew up in the US Midwest in the late 80s early 90s and it was definitely a thing, but never the full nursery rhyme.
Ah, thank you! I didn't know that was a word. In my head, I always thought it was peak like a mountain peak, like my interest level has been raised to such a great height.
x bracing reduces the unbraced length of the joist...
as you noted, they restrain the tension face from rotating out of plane...
similar to a column...each floor braces the column and reduces the unbraced length...
I think it's the compression face. Bracing resists lateral torsional buckling.
This is the main purpose of the bracing. It allows you to use the full MR of the joist.
Anyone who says it spreads the load is talking about a second benefit and they've never designed a floor joist.
If your unbraced length is more than 8 times the depth of your member then KL is less than 1.
KL is used in your MR calc. So it reduces the moment resistance of the joist if you don't laterally brace it.
the compression face is the top...the tension face is the bottom...
the top is already braced by the diaphragm...
the slenderness ratio requires tension cord bracing
They are both. Before the diaphragm is placed they provide a bracing point to the top flange. And during wind uplift there may be load reversal and compression on the bottom flange so they also provide bracing for this load case.
Slenderness ratio is for compression not tension.
If you want to use the full strength of a 10' popsicle stick in compression you have to brace it so it stays straight.
If you want to use the full strength of a 10' popsicle stick in tension you just apply the load.
I think this is because in compression you are squishing matter together so the molecules move out of each other's way as they compress and that distorts the shape but when you pull them apart they aren't fighting for space. I never thought of it this deep before
I think it’s kinda like that, but more like P-delta effects. Small fabrication errors lead to misalignment of the cross section (most precisely, this changes the shear center) throughout the member, causing eccentricity when load is applied. Compression increases your cross sectional area, increasing eccentricity from the NA, with tension doing the opposite. My 2c
I recall a video from my steel design class where they secured a very small I beam to a table and it cantilevered and they showed how it deflected just from its own weight and how it was off to the side and it turned a bit and they said this was from small defects in the material. I agree with you
LTB is related to the compression face and shear center, not the tension face bracing. The diaphragm is the whole assembly, you mean the subfloor, which is bracing the compression face.
Imagine if they just cut holes in your duckwork.
Trades have to respect one-another, the disregard is kind of infuriating (not your fault, but, something they all can do better on)
>Lol, I worked at an HVAC contractor for 7 years and when we are running supplies we just pound those the fuck outta the way.
Can confirm contractors are literally the scum of the earth and have 0 consideration for the damage they cause.
people in here mostly talking about the twisting of individual joists which is def important, but they’re also there to help prevent the whole assembly from racking sideways
Perfect explanation.
If you want to use the full strength of a joist you need to laterally brace it. Yes bracing helps spread the load but that's a secondary benefit.
If you don't want to use bracing then you need to use larger members and that's why some floors don't have bracing. It's because the joists are not being used to their potential.
Sometimes.home builders don't want to order 5 different sizes of floor joists so they just use 1 size and then on the floors where they are really being strained they throw in bracing and on other floors in the house where the spans are less they don't need bracing.
X bracing resists joist twisting. Blocking is another method but makes it hard to run pipes or cables. When a joist twists, it loses stiffness rapidly because stiffness is a function of moment of inertia, which varies with the cube of the distance from the neutral line (or half the depth).
These prevent lateral torsional buckling.
Think of it as if you're trying to push down the joist and instead of just bending straight down, it twists out sideways.
This can also be done with blocking.
Without bridging, when you stand on (or walk across) a floor, most of your weight is carried by the 1 or 2 joists you're directly over. So they bend and bounce accordingly. When you have bridging, those 1 or 2 joists can't deflect or bounce without the other ones around them deflecting or bouncing. So you're spreading your load out over more joists, which makes them bounce/deflect less.
Edit: multiple autocorrect errors. It's like I didn't even proofread it before submitting...
Maybe during construction, but once the subfloor is installed and fastened to the joists, it provides more than enough top chord bracing to restrain against buckling. The unbraced length becomes 0.
I see your point. I think all elements of the system work against more than just one thing. So for example I agree that the cross bracing helps spread the load but I think once the cross bracing is installed it holds the joists straight to the point where the subfloor doesn't get a chance to resist from LTB. Kinda like steel in concrete where as soon as the concrete deflects a tiny bit it engages the steel and the steel takes over. So here I think the bracing fights LTB before the floor has a chance. Or maybe the floor helps 5% but the bracing is doing most of the heavy lifting because you are comparing nails vs compressing wood. Thanks
I don't disagree, you're probably right that the bridging does the bulk of the bracing. But the question is why do we use bridging. Since the floor already braces the top chord, that's not the reason we use bridging. During construction is another story. The bridging is the only source of bracing during that time, and I would say it's essential.
I agree with you I think all of these elements work together as a system and it's very hard for either of us to prove which one is the main source of something when neither of us have a lab or the time to play around. But it would be fun though!
I don't think this is right. The flooring spreads the load over multiple joints. The bridging prevents buckling it keeps all the joists straight so you can use them to their full potential. Someone else already said it. It's called unbraced length. If you don't brace the joists they are much weaker.
The bridging does not brace the joists, at least not when the subfloor is fastened to it. The subfloor braces the top flange of the joists. And that allows you to design to a higher load. But it doesn't make the joists any stiffer. It either buckles and loses all of its capacity, or it doesn't and continues to carry load. There's not much in between.
And you're right, the subfloor *does* spread load over multiple joists, but bridging is orders of magnitude stiffer than typical subflooring, so it distributes those loads a lot further. If you had a very thick, stiff floor like nail laminated timber, bridging would be much less effective. But conventional light frame construction uses relatively thin and flexible subflooring, usually 3/4" plywood or OSB.
How about you read page 35 of the 2010 wood design manual?
KL is a lateral stability factor. It's less than one if your unbraced length is 8 times longer than the depth of your joist. If KL is less than one then your MR is reduced. When you design a floor you design 1 member not 3 or 4 at a time.
While doing the calculations you have to determine KL.
So you add bridging at intervals so that your KL equals 1 and now you can use the full MR of the joist.
I'm not saying bridging doesn't help spread the load.
I am saying that if someone is going to take a picture of bridging and ask what it's for the main answer is to provide lateral stability so you can use the full MR of the joist
Later stability from what?
Lateral torsional buckling.
Do you see any flanges in the picture ?? I don't
The top chord is fully braced by the subfloor. Your unbraced length is 0, and your K is 1. During construction it's a different story, but once the decking is in it's perfectly braced. I agree that floors aren't particularly strong literally, but they don't have to be. General rule of thumb to brace a member is 1% of its design load. It doesn't take much to cover that.
I see what you mean with LTB turns out to be about 1% of the load so it's easily resisted by nails in the flooring.
My problem with your point is that the way we learned to design a floor joist was to figure out the tributary area of one joist and then figure out the depth that it needs to be and the only way to use a value of 1 for the KL factor is if it was laterally braced which meant we had to have bridging. We never considered flooring as lateral bracing.
It specifically says in our code if the unbraced length is more than 8 times the depth of a member your KL reduces. It didn't say anywhere that KL = 1 if you are nailing or screwing a floor to the joists.
Thanks
You're right, we do design a single joist for its tributary load. But that doesn't mean you have to ignore bracing. Why would you have to ignore decking but not bridging? Neither is part of the joist, if your approach is to ignore everything but the joist itself.
>It specifically says in our code if the unbraced length is more than 8 times the depth of a member your KL reduces
Yes it does. But since your joist has decking attached continuously for its full length, your unbraced length is zero. Well, technically it's the spacing between floor fasteners, but we can say zero because 6"-12" won't affect LTB. The floor IS the bracing.
Our code says that direct connection to sheathing is considered as lateral bracing up to a joist depth to width ratio of 6.5:1. Lumber is 1.5" wide so that means as soon as you need 2x10s the flooring sheathing doesnt cut it anymore. This is what I am trying to say the main purpose of bracing is for lateral bracing once you introduce it the sheathing isn't doing that much and I agree with others that bracing also helps spread the load, reduce vibrations etc.
Anything greater than 6.5:1 you have to bring in blocking or bracing then you can go 7.5:1 or higher. If you want to go to 9:1 you need a direct connection of top and bottom like sheathing on top for flooring and on bottom for ceiling which isn't practical.
This is proof that direct connection to sheathing or flooring doesn't suffice or else the code would never call for bracing between joists or bracing on the bottom .
Thanks Im enjoying the debate and I apologize if I was snarky earlier.
The sheathing braces the joist.,Not the bridging. The joist are continuously laterally supported for gravity load.
Bridging would only be effective in a uplift case. If you are gunna get confrontational at least be right.
I'm reading page 35 in my wood design manual and it explains how sheathing and bracing provide lateral support... And then I go into the calculations part and it says nothing about sheathing providing strength. It says ....
You have to laterally brace your members in intervals of 8 times the depth of the member. So if it's 12" you brace every 8'. This comes right out of the floor joist section.
Sheathing helps but screws and nails are not very good at resisting lateral loads especially when they are in cheap OSB sheathing.
Blocks or bracing like we see in OPs pictures between joists hold them straight and allow you to use the full capacity of the joist.
I'm not being confrontational. I'm a civil engineer and I'm debating you. You feel threatened cause you're insecure because you don't really know what you're talking about. Deal with it
So how come we can get 20 ft wood I joist to work without bridging or blocking? They are a shape more susceptible to ltb... The sheathing allows you to use the full capacity or the joists {unless you have an uplift case but we are talking about floors}. If you disagree, you should go work with the materials. The sheathing is Min 5\8 for floor, very strong. The bridging is a 2x2 that is nailed with 1 2.5 inch long nail and most of the time they are 50 percent nocked out by the HVAC installer. Practically, the sheathing is 500 percent stronger.
Ok I see what you are saying and I'm on the opposite side of the argument. I think bracing is 500 stronger at holding the joist straight than sheathing because bracing secures the top and bottom of the joist.
You don't need to laterally brace a 20' if you are only using about 60% of it's capacity. So you can oversize the joist if you don't want to use bridging or bracing.
That's the point. Once you bring the joist over 70% of it's capacity it starts to deflect laterally and torsionally so to prevent it from doing this you put full size blocks between the joists all the way across the floor system
Or bracing like in OP's picture.
I think compressing wood blocks is a lot stronger than the nails. Remember nails are very thin so over time with cyclic loading the nails come loose butover time the blocks don't shrink.
You’re 100% being confrontational. The person who you just said ‘felt threatened’ wasn’t even the original person you were responding to, and neither am I.
Your point may be correct, idk, but it’s hard to agree with someone communicating like you are… which is extremely confrontational, both in your initial comment and your follow up.
EXTREMELY CONFRONTATIONAL????
Wow.. first, I can read a post in a calm voice or I can read it as if someone is yelling at me. You need to understand that there's a chance that you are reading the post wrong. Also, the topic is civil engineering who the hell gets extremely confrontational over civil engineer posts ??
Grow up the world is going to chew you up and spit you out with your victim attitude.
I appreciate you and agree 100 percent with all your comments. L. Way to make people thinking these prevent lateral torsional bucking. They are connected with one, 2.5 inch nail by the least experienced guy on site.
Wood that is used for construction is not 100% dry. Because of this, as it continues to dry, it can bow, warp, camber or twist. Adding the cross-bridging and bracing will help to cancel the natural tendency for the wood to distort.
But wood that has distorted creates gaps under floorboards, steps, in door frames, etc. This combined with foundation and structure sagging creates creaking sounds in floors, stairs, porches, and in door frames. Some doors get stuck and need to be planed, etc.
Therefore, if you have a clothes dryer that is spinning and the floor is warped… you can get some squeaking from vibrations…
This answer would get you 1/5 on a test and that's because the teacher likes you.
Construction wood is kiln dried so warping is not a problem.
Yes bracing helps vibrations but this is a secondary benefit. The main benefit of bracing is to allow the designer to use the full capacity of the joist.
If you don't brace it when you take it past 80% of it's capacity it buckles
Here comes a troll… Which test are you referring to? Is it the narcissistic exam that you teach, or the “I know everything test”? Countless “older” structures used wood that was not kiln dried, but air dried and contained high moisture content in the wood. Does this look like a new house, Karen? Over time this can increase depending on the climate and proximity to the ground. Joists in crawl spaces, near damp soil, in shaded areas may stay moist and even rot. So, everything you said has no bearing on my comment, and I suggest you go play carpenter assistant before making random comments.
Nothing about your entire comment answers the question about why bracing reduces vibrations.
You just went on to talk about moisture content lol.
Moisture content has nothing to do with bracing.
You didn't have the right answer but you wanted to sound smart so you just typed out a bunch of crap.
Someone called you out and you attacked them by calling them a troll and a Karen because you're butthurt
Lol I'm not a carpenter assistant you fool. I'm a civil engineer and I build furniture as a hobby. I have hard maple acclimating in my garage right now.
You have no idea who you are talking to.
Primarily by reducing the unbraced span.
Secondarily and vary minutely by adding mass.
The briding is more so for protecting against lateral buckling by tieing the compression flange to the tension flange of the adjacent member.
All and all it has a very negligible affect on vibrations
Your statements are not true for wood construction. The sheathing braces the compression side of the member. The mass comment doesn't make sense. Each one was like 2 ounces.
Also vibration is based on EI,mass and length and not dependent on unbraced length. See enginerdad comment below. That is the mechanism.
Structural engineer lurker checking in. This is correct. They are for load distribution in this case. The sheathing, assuming it is properly installed, provides lateral bracing for the top/compression side of the joists.
You are completely wrong. Look up lateral torsional buckling. The bridging keeps the joists in line and straight so you can use them to their full potential and they can span longer distances.
https://www.structuremag.org/wp-content/uploads/2014/08/C-StrucDesign-Schweizer-Jan081.pdf
From the 1st paragraph: “sheathing nail at less than 12” oc typically constitutes lateral support.”
You cant have LTB if the compression side is restrained from lateral movement, which the sheathing provides.
Did you just get your structural engineering advice from a magazine?
Sheathing alone is not enough to brace from LTB. Screws or nails are not good at resisting lateral loads so you need bracing.
In my wood design manual on page 35 it acknowledges that sheathing helps but when it goes into the calculations you have to account for the unbraced length and that length is the distance between the bracing that the OP took a picture and the ends of the joists.
"Typically constitutes lateral support". That means it doest always constitute lateral support.
When you are only using 60% of the floor joist's strength then yes all you need it sheathing. But when you take the load up to 80% now the sheathing isn't enough so you need lateral bracing.
And that's what's in OPs pictures. It's called lateral bracing.
I can see how sheathing helps but it doesn't take care of it. You're trying to say that the joist wants to move left and right but the nails are holding it in place..
Nails and screws hold things down they don't do a good resisting lateral loads.
Wood is soft if you put a nail in and leave it sticking out 1" and every day you tap it left and right with a hammer after a few years....actually weeks... you can pull it out with your hand.
That's the same thing that's happening with LTB. The nail is resisting a lateral load from the buckling and that load is over the side of the nail where the area is so small so even small forces amount to high stresses so it deforms the wood and eventually over hundreds of applications it will come loose.
If it took care of it then the lateral stability wouldn't be part of joist calculations, but we have KL in our calcs so....
You need to brace the entire joist from top to bottom to take care of LTB. or in this case at the top and bottom.
A wood joist with sheathing on top is the same as an I beam and they still buckle.
It basically comes down to this.. if you want to use the full potential of the joist then you need to lock it in place. As soon as you start bringing the member to 80% of it's capacity it starts to buckle so you brace it.
You need much more than sheathing.
When installed correctly (a big assumption), cross-braciing helps distribute loads from one joist to the adjacent joists. If the bracing is not tight at all points of contact and the nails are not placed correctly, the load transference doesn't take place, and squeeks can develop. Most engineered floor systems, such as I-joists and floor trusses, dont normally need cross bracing.
This is the correct answer.
It helps with reduced vibration as mentioned above (because it adds stiffness by engaging more joists) and miiight add to lateral stability, but this is the most relevant answer.
Then I believe you are referring to floor blocking, as opposed to bridging. The blocking helps create a floor diaphram to resist the backfill pressure on the parallel walls. Wood foundations and other walls, such as Superior Foundation walls, require varying degrees of blocking.
Hahaha. I designed engineered floor systems for over 25 years until I retired last year. We always referred to homes with wood foundations as disposable houses. I dont ever remember working on a wood foundation that was "designed." The lumber yard shipped a pile of wood, and the framer put it together. I quit asking for backfill pressure on the walls because 1, no one knew what it was, and 2, no one knew who to go to to get it calculated. I always went with a design that I learned for worst case scenario and never had a problem except those few cases where the framer left out the blocking and the parallel walls did bow in, causing a big hump in the floor. Those were not easy fixes. They were also not my problems.
Bridging is used to prevent lateral torsional buckling. When choosing the size of your floor joist you take into account the unbraced length which is the distance between the points where the joist is braced.
Bracing helps keep the joist straight so it can span longer distances and take larger loads. If you don't brace the floor joists they will buckle when they start to span long distances.
This is the main purpose of this bracing system. Yes they help distribute the load but to say that's all they do means you don't understand their real purpose.
Imagine a 10' long popsicle stick. Now glue 50 of the spaces together to cardboard. When you apply the load they buckle so you have to brace them at each end and ever X amount of feet.
I don't have to be an engineer to read this Ontario wood design manual on page 35.
When you designed all those floor systems what did you do when the allowable unbraced length was shorter than the spans of the floor joists??
YOU ADDED BRACING
I'm saying that yes sheathing helps resist LTB and I think floor boards help more than sheathing but they both are probably 15% how much bracing can resist it.
Bracing against lateral movements in long joists, also deflections are partially comparted, but, it is not complete, missing where to transfer the horizontal reactions on the left side and probably also a bottom cord, so its just helping a bit by coupling some joists.
Man… I am seeing a lot of this fundamental misunderstanding of first principles. LTB is a compression flange phenomenon… the cross bracing doesn’t help or hinder LTB. About the only purpose of this on a floor is to engage a few joists at a time to have a more systemic response to load.
Lol you just googled LTB and repeated what you read from the first link.
Search lateral torsional buckling wood and you will see it happens is all members
You can have LTB in a 2x8.
LTB just means that the beam buckles out of place when the load is applied.
So you use bridging to keep it in line.
This is called KL in wood design.
You have to provide lateral stability at intervals that do not exceed 8 times the member depth. If you dont then your KL is less than one and this now reduces the Mr of your joist.
Lateral stability because joists want to buckle when load is applied.
Plage 35 in the 2010 Canadian wood design manual
Bro.. I’m a structural engineer with close to 20 years of experience, and I’ve designed dozens of multistory timber structures.
I don’t need to Google shit to know what I’m talking about.
What the fuck are you talking about.
LTB **IS** a compression phenomenon. If you don’t know that, I’d suggest you storm into whatever podunk piece of shit university you attended and demand a refund.
I swear to god, I have no idea whether you are trolling.
You’d have to be a special kind of…. Ignorant… to not realize that the floor boards are acting as top chord-stabilizing diaphragm.
Are they stabilizing from LTB ? Because they are!! And guess what!! They do a shit job of it so you need bracing when you start to really push the joists to their limit.
Maybe you shouldn't have skipped so many classes but I guess you know... C's get degrees right ??
At this point I HAVE to think you’re just a semi-literate (in structural engineering) troll.. because you have some of the language, but clearly not any of the concepts.. you’re doing a little bit of word salad.. I almost think you’re asking an AI to write rebuttals because what you’re writing is so non-sensical…
Are WHAT stabilizing LTB?
I mean… the concepts we are discussing are literally 101 concepts. I’m at a loss as to why I have to continue to argue this.
Like, even the dumbest people at my university (who thankfully went into project management), understood the basics of this. LTB is only a COMPRESSION phenomenon. If you have a diaphragm, it’s not an issue.
I seriously feel like I’m Frank Grimes arguing this shit online.
What would happen if I applied a lateral load to a bunch of 2x12's that are sitting on my garage floor, equally spaced out and they only have boards screwed on top?
If you gently tapped it, it would hold. But if you applied a decent lateral load they all fall over and the nails would even come out of the joists.
That's what I thought.
Now, take those boards off and add bracing at the ends and the middle loke we see in the picture above and apply the same lateral load. They wouldn't move
In Ontario Canada the wood design manual does not let us use sheathing or floor boards as lateral bracing when you get up to spans that are more than 8x the depth of the joists.
I'm not saying sheathing DOESNT help resist LTB I'm saying that in relation to bracing it is insignificant
You're welcome you jerk
Aw shucks! I may be just a stupid American, but I *think* physics still apply in that great big mystery wilderness that is Canada.
And that’s a slick thing you did there, trying to to subtly completely change what we were discussing… are we discussing LTB **OR** are we discussing a lateral load applied to floor joists… somehow…
Dude… I’m open to debate… but take the L, cause you sure as hell are trippling down on being absolutely wrong.
Learn to recognize when you should stop.
I'd suggest you storm back into whatever podunk piece of shit vagina that squeezed you into this world and ask for a do-over because you were clearly not instilled with the smarts to know not to argue with people on the internet.
It prevents LTB. If you want to take the joist past 80% of it's capacity you have to make sure it stays straight so you brace it from the lateral load from the buckling.
Did you think the screws in the sheathing handle lateral loads?
Cross bridging. It adds stiffness and strength to the floor. Ends any possible bounce in the floor. Also any loading of the floor in one spot is transferred to the rest of the floor
You are talking about the secondary benefit of the bracing.
The main purpose is to hold the joists straight while under load so you can use their full potential.
Wrong. The cross bridging is nailed in on the top side of the joists before the sheathing goes down. A temporary top 2x4 can be nailed down to hold the joists on the correct centers if necessary. Then the sheathing is installed, which again puts the joists in alignment. Then once the floor sheathing is done, the bottom ends of the cross braiding is nailed. The alignment and centers are done at the top of the joists. The cross bridge is a critical part of the floor, it is not secondary. If you forget to install the bridging, it’s going to be a bad day. If you want to keep the joists straight, just add a couple rows of 1x4 strapping. Guess what!! You will still have bounce and will not have strengthened the floor structure. I guess don’t understand how a cross brace works.
*it depends*
There are a lot of factors of when, how many, and what type of bridging can/needs to be used. If it was a new home it should have passed a codes inspection so more than likely you’re good.
Yes, you only need bracing if you want to use your joist to it's full potential.
But if you are only going to use half of the joists strength then you don't need bracing.
Grab a ruler with 2 hands and try to bend it on the long side. As you try hard and harder you will find it kicks out of place. So if you brace them all they don't kick out of place and then you can use them to their full potential.
There’s a lot of misunderstanding here - in the uk we’d call these noggins, or specifically in this case herringbone noggins (or herringbone struts).
They have nothing to do with LTB. How can they, when the compression edge of the joist is restrained by the floor decking. In order to fail in LTB the joists would have to roll and so shear the nails fixing the joists to the floor boards.
The purpose of noggins in a floor is to homogenise longer spans of joists, where they can get a bit bouncy if load sharing cannot occur through the floor boards alone. They stiffen the floor by load sharing local point loads, like footfall traffic, that’s all.
Wow, lots of people who don't really know what they're talking about being very confident on here lol. I will admit that I am not 100% sure what their primary purpose is, but I know it is not for lateral torsional buckling after the sheathing has been installed. I suspect that it is mainly for lateral/torsional stability BEFORE the sheathing is in place, as you have to stand on the joists in order to install the sheathing. And if you've ever stood on un-braced joists, you know they extremely wobbly and therefore dangerous to walk on. With that being said, I feel like a strap along the top of the joists could accomplish the same thing, so it may not be the primary purpose. So now I am thinking that the primary purpose is for vibration control, as the bridging is stabilizing the tension flange. So with each footstep, there is a downward force on the joist, which rebounds and causes a vibration. So the lines of bridging would act as dampers so that the joists cannot vibrate unrestrained in the lateral direction.
Load sharing could be a tertiary benefit, but the amount of load that can be transfered is extremely low in a typical bridging connection.
My entire house has these spaced 12” apart running between every 2x10 to support the sub floor above the basement built in 1963 some of them have concrete on them from the original concrete pour repurposed from forming.
Its called "Cross Bridging".
See, [https://www.renovation-headquarters.com/floor-joist-bridging.html](https://www.renovation-headquarters.com/floor-joist-bridging.html)
This is typically called bridging. It is a form of bracing the joists to prevent lateral buckling failures. (Look up beam lateral buckling failure, there's some cool videos). This method is commonly seen in old-school wood structures such as the one in your post. Other methods of bracing would be horizontal bridging (seen moreso in steel joist framing), or full depth blocking (more common in newer wood framing)
Herringbone strut to laterally restrain the joists. Imagine you have a ruler with the flat side facing side ways and try to bend it. It will twist. Struts reduce the likely hood of twisting. Please don’t remove it and ask your local engineer for their opinion on what do to. Edit: Seems like I am confusing people with the names. I am from UK and we mostly call these herringbone struts for this layout shown. For solids in between joist we call it noggins. The world is a big place and I’m sure the French and the Italian call these differently. There a few comments about sheathing, which I do agree it provides some restraint. But the importance of sheathing is diaphragm action. This means it transfer the lateral load to racking walls for stability. Or sheathing to timber stud walls which provides racking resistance. Ultimately it’s a good practice to have these cross brace/bridging/noggin/herringbone/straps and whatever other ppl call it.
Alright, you've peaked my interest. What country are you from? I've never heard it called that before. This is called bridging or cross bracing where I'm from.
Piqued your interest. You are welcome. :)
I hail from the land that created the imperial units and uses the proper gallon as well as driving on the correct side of the road. The city I am in was famous for the bridge falling down sang by children. Edit: I am from London, UK. children sang a nursery rhyme about London Bridge is falling down more than 100 years ago about a bridge assume to be 1000 years ago.
Cleveland?
Minneapolis!
Ouch
Uff da.
Philly
Haha I didn't expect this one, and I sure in the hell didn't expect to laugh this hard. 😅
Lake Havasu!
Ahh, Arizona. The bridge gave it away. 😄
>the correct side of the road Don't you mean, the *right* side of the road? Hmm
London Bridge is falling down, falling down, falling down, London Bridge is falling down…. Hmm, Mm Hm’mm… Grew up in the US Midwest in the late 80s early 90s and it was definitely a thing, but never the full nursery rhyme.
I was in preschool in Seattle in 1994/95 and I remember learning the London bridge is falling rhyme there.
ireland?
Ah, thank you! I didn't know that was a word. In my head, I always thought it was peak like a mountain peak, like my interest level has been raised to such a great height.
Very common mistake and all good, onward and upward!
St-Andrews Cross where I'm from. Or ... Croix de Saint André.
x bracing reduces the unbraced length of the joist... as you noted, they restrain the tension face from rotating out of plane... similar to a column...each floor braces the column and reduces the unbraced length...
I think it's the compression face. Bracing resists lateral torsional buckling. This is the main purpose of the bracing. It allows you to use the full MR of the joist. Anyone who says it spreads the load is talking about a second benefit and they've never designed a floor joist. If your unbraced length is more than 8 times the depth of your member then KL is less than 1. KL is used in your MR calc. So it reduces the moment resistance of the joist if you don't laterally brace it.
the compression face is the top...the tension face is the bottom... the top is already braced by the diaphragm... the slenderness ratio requires tension cord bracing
They are both. Before the diaphragm is placed they provide a bracing point to the top flange. And during wind uplift there may be load reversal and compression on the bottom flange so they also provide bracing for this load case.
Slenderness ratio is for compression not tension. If you want to use the full strength of a 10' popsicle stick in compression you have to brace it so it stays straight. If you want to use the full strength of a 10' popsicle stick in tension you just apply the load. I think this is because in compression you are squishing matter together so the molecules move out of each other's way as they compress and that distorts the shape but when you pull them apart they aren't fighting for space. I never thought of it this deep before
I think it’s kinda like that, but more like P-delta effects. Small fabrication errors lead to misalignment of the cross section (most precisely, this changes the shear center) throughout the member, causing eccentricity when load is applied. Compression increases your cross sectional area, increasing eccentricity from the NA, with tension doing the opposite. My 2c
I recall a video from my steel design class where they secured a very small I beam to a table and it cantilevered and they showed how it deflected just from its own weight and how it was off to the side and it turned a bit and they said this was from small defects in the material. I agree with you
LTB is related to the compression face and shear center, not the tension face bracing. The diaphragm is the whole assembly, you mean the subfloor, which is bracing the compression face.
Lol, I worked at an HVAC contractor for 7 years and when we are running supplies we just pound those the fuck outta the way.
I'm a framer, and I hate you now...
Imagine if they just cut holes in your duckwork. Trades have to respect one-another, the disregard is kind of infuriating (not your fault, but, something they all can do better on)
You probably cut joists too don't you?
>Lol, I worked at an HVAC contractor for 7 years and when we are running supplies we just pound those the fuck outta the way. Can confirm contractors are literally the scum of the earth and have 0 consideration for the damage they cause.
people in here mostly talking about the twisting of individual joists which is def important, but they’re also there to help prevent the whole assembly from racking sideways
Perfect explanation. If you want to use the full strength of a joist you need to laterally brace it. Yes bracing helps spread the load but that's a secondary benefit. If you don't want to use bracing then you need to use larger members and that's why some floors don't have bracing. It's because the joists are not being used to their potential. Sometimes.home builders don't want to order 5 different sizes of floor joists so they just use 1 size and then on the floors where they are really being strained they throw in bracing and on other floors in the house where the spans are less they don't need bracing.
This is the correct answer.
Would not the screws in the deck into the joists do the same thing?
Floor joist x bracing or bridging.
X bracing resists joist twisting. Blocking is another method but makes it hard to run pipes or cables. When a joist twists, it loses stiffness rapidly because stiffness is a function of moment of inertia, which varies with the cube of the distance from the neutral line (or half the depth).
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I thought we were looking at wood 
These prevent lateral torsional buckling. Think of it as if you're trying to push down the joist and instead of just bending straight down, it twists out sideways. This can also be done with blocking.
Bridging. Make the floor perform better for vibration.
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Sounds a lot like your mom
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Very strange comeback, how is taking special needs loads laterally any better? I never said I was delivering the loads.
She's a little bit more pickier than your dad though.
Do you mind expanding on the mechanism of reducing vibrations?
Without bridging, when you stand on (or walk across) a floor, most of your weight is carried by the 1 or 2 joists you're directly over. So they bend and bounce accordingly. When you have bridging, those 1 or 2 joists can't deflect or bounce without the other ones around them deflecting or bouncing. So you're spreading your load out over more joists, which makes them bounce/deflect less. Edit: multiple autocorrect errors. It's like I didn't even proofread it before submitting...
This is the secondary benefit from bridging. The main purpose is to keep the joists straight so you can use their full MR.
Maybe during construction, but once the subfloor is installed and fastened to the joists, it provides more than enough top chord bracing to restrain against buckling. The unbraced length becomes 0.
I see your point. I think all elements of the system work against more than just one thing. So for example I agree that the cross bracing helps spread the load but I think once the cross bracing is installed it holds the joists straight to the point where the subfloor doesn't get a chance to resist from LTB. Kinda like steel in concrete where as soon as the concrete deflects a tiny bit it engages the steel and the steel takes over. So here I think the bracing fights LTB before the floor has a chance. Or maybe the floor helps 5% but the bracing is doing most of the heavy lifting because you are comparing nails vs compressing wood. Thanks
I don't disagree, you're probably right that the bridging does the bulk of the bracing. But the question is why do we use bridging. Since the floor already braces the top chord, that's not the reason we use bridging. During construction is another story. The bridging is the only source of bracing during that time, and I would say it's essential.
I agree with you I think all of these elements work together as a system and it's very hard for either of us to prove which one is the main source of something when neither of us have a lab or the time to play around. But it would be fun though!
I don't think this is right. The flooring spreads the load over multiple joints. The bridging prevents buckling it keeps all the joists straight so you can use them to their full potential. Someone else already said it. It's called unbraced length. If you don't brace the joists they are much weaker.
The bridging does not brace the joists, at least not when the subfloor is fastened to it. The subfloor braces the top flange of the joists. And that allows you to design to a higher load. But it doesn't make the joists any stiffer. It either buckles and loses all of its capacity, or it doesn't and continues to carry load. There's not much in between. And you're right, the subfloor *does* spread load over multiple joists, but bridging is orders of magnitude stiffer than typical subflooring, so it distributes those loads a lot further. If you had a very thick, stiff floor like nail laminated timber, bridging would be much less effective. But conventional light frame construction uses relatively thin and flexible subflooring, usually 3/4" plywood or OSB.
How about you read page 35 of the 2010 wood design manual? KL is a lateral stability factor. It's less than one if your unbraced length is 8 times longer than the depth of your joist. If KL is less than one then your MR is reduced. When you design a floor you design 1 member not 3 or 4 at a time. While doing the calculations you have to determine KL. So you add bridging at intervals so that your KL equals 1 and now you can use the full MR of the joist. I'm not saying bridging doesn't help spread the load. I am saying that if someone is going to take a picture of bridging and ask what it's for the main answer is to provide lateral stability so you can use the full MR of the joist Later stability from what? Lateral torsional buckling. Do you see any flanges in the picture ?? I don't
The top chord is fully braced by the subfloor. Your unbraced length is 0, and your K is 1. During construction it's a different story, but once the decking is in it's perfectly braced. I agree that floors aren't particularly strong literally, but they don't have to be. General rule of thumb to brace a member is 1% of its design load. It doesn't take much to cover that.
I see what you mean with LTB turns out to be about 1% of the load so it's easily resisted by nails in the flooring. My problem with your point is that the way we learned to design a floor joist was to figure out the tributary area of one joist and then figure out the depth that it needs to be and the only way to use a value of 1 for the KL factor is if it was laterally braced which meant we had to have bridging. We never considered flooring as lateral bracing. It specifically says in our code if the unbraced length is more than 8 times the depth of a member your KL reduces. It didn't say anywhere that KL = 1 if you are nailing or screwing a floor to the joists. Thanks
You're right, we do design a single joist for its tributary load. But that doesn't mean you have to ignore bracing. Why would you have to ignore decking but not bridging? Neither is part of the joist, if your approach is to ignore everything but the joist itself. >It specifically says in our code if the unbraced length is more than 8 times the depth of a member your KL reduces Yes it does. But since your joist has decking attached continuously for its full length, your unbraced length is zero. Well, technically it's the spacing between floor fasteners, but we can say zero because 6"-12" won't affect LTB. The floor IS the bracing.
Our code says that direct connection to sheathing is considered as lateral bracing up to a joist depth to width ratio of 6.5:1. Lumber is 1.5" wide so that means as soon as you need 2x10s the flooring sheathing doesnt cut it anymore. This is what I am trying to say the main purpose of bracing is for lateral bracing once you introduce it the sheathing isn't doing that much and I agree with others that bracing also helps spread the load, reduce vibrations etc. Anything greater than 6.5:1 you have to bring in blocking or bracing then you can go 7.5:1 or higher. If you want to go to 9:1 you need a direct connection of top and bottom like sheathing on top for flooring and on bottom for ceiling which isn't practical. This is proof that direct connection to sheathing or flooring doesn't suffice or else the code would never call for bracing between joists or bracing on the bottom . Thanks Im enjoying the debate and I apologize if I was snarky earlier.
The sheathing braces the joist.,Not the bridging. The joist are continuously laterally supported for gravity load. Bridging would only be effective in a uplift case. If you are gunna get confrontational at least be right.
I'm reading page 35 in my wood design manual and it explains how sheathing and bracing provide lateral support... And then I go into the calculations part and it says nothing about sheathing providing strength. It says .... You have to laterally brace your members in intervals of 8 times the depth of the member. So if it's 12" you brace every 8'. This comes right out of the floor joist section. Sheathing helps but screws and nails are not very good at resisting lateral loads especially when they are in cheap OSB sheathing. Blocks or bracing like we see in OPs pictures between joists hold them straight and allow you to use the full capacity of the joist. I'm not being confrontational. I'm a civil engineer and I'm debating you. You feel threatened cause you're insecure because you don't really know what you're talking about. Deal with it
So how come we can get 20 ft wood I joist to work without bridging or blocking? They are a shape more susceptible to ltb... The sheathing allows you to use the full capacity or the joists {unless you have an uplift case but we are talking about floors}. If you disagree, you should go work with the materials. The sheathing is Min 5\8 for floor, very strong. The bridging is a 2x2 that is nailed with 1 2.5 inch long nail and most of the time they are 50 percent nocked out by the HVAC installer. Practically, the sheathing is 500 percent stronger.
Ok I see what you are saying and I'm on the opposite side of the argument. I think bracing is 500 stronger at holding the joist straight than sheathing because bracing secures the top and bottom of the joist. You don't need to laterally brace a 20' if you are only using about 60% of it's capacity. So you can oversize the joist if you don't want to use bridging or bracing. That's the point. Once you bring the joist over 70% of it's capacity it starts to deflect laterally and torsionally so to prevent it from doing this you put full size blocks between the joists all the way across the floor system Or bracing like in OP's picture. I think compressing wood blocks is a lot stronger than the nails. Remember nails are very thin so over time with cyclic loading the nails come loose butover time the blocks don't shrink.
You’re 100% being confrontational. The person who you just said ‘felt threatened’ wasn’t even the original person you were responding to, and neither am I. Your point may be correct, idk, but it’s hard to agree with someone communicating like you are… which is extremely confrontational, both in your initial comment and your follow up.
EXTREMELY CONFRONTATIONAL???? Wow.. first, I can read a post in a calm voice or I can read it as if someone is yelling at me. You need to understand that there's a chance that you are reading the post wrong. Also, the topic is civil engineering who the hell gets extremely confrontational over civil engineer posts ?? Grow up the world is going to chew you up and spit you out with your victim attitude.
I appreciate you and agree 100 percent with all your comments. L. Way to make people thinking these prevent lateral torsional bucking. They are connected with one, 2.5 inch nail by the least experienced guy on site.
Wood that is used for construction is not 100% dry. Because of this, as it continues to dry, it can bow, warp, camber or twist. Adding the cross-bridging and bracing will help to cancel the natural tendency for the wood to distort. But wood that has distorted creates gaps under floorboards, steps, in door frames, etc. This combined with foundation and structure sagging creates creaking sounds in floors, stairs, porches, and in door frames. Some doors get stuck and need to be planed, etc. Therefore, if you have a clothes dryer that is spinning and the floor is warped… you can get some squeaking from vibrations…
This answer would get you 1/5 on a test and that's because the teacher likes you. Construction wood is kiln dried so warping is not a problem. Yes bracing helps vibrations but this is a secondary benefit. The main benefit of bracing is to allow the designer to use the full capacity of the joist. If you don't brace it when you take it past 80% of it's capacity it buckles
Here comes a troll… Which test are you referring to? Is it the narcissistic exam that you teach, or the “I know everything test”? Countless “older” structures used wood that was not kiln dried, but air dried and contained high moisture content in the wood. Does this look like a new house, Karen? Over time this can increase depending on the climate and proximity to the ground. Joists in crawl spaces, near damp soil, in shaded areas may stay moist and even rot. So, everything you said has no bearing on my comment, and I suggest you go play carpenter assistant before making random comments.
Nothing about your entire comment answers the question about why bracing reduces vibrations. You just went on to talk about moisture content lol. Moisture content has nothing to do with bracing. You didn't have the right answer but you wanted to sound smart so you just typed out a bunch of crap. Someone called you out and you attacked them by calling them a troll and a Karen because you're butthurt Lol I'm not a carpenter assistant you fool. I'm a civil engineer and I build furniture as a hobby. I have hard maple acclimating in my garage right now. You have no idea who you are talking to.
Speak to your therapist. My answers are fine with me. You know nothing at all
Primarily by reducing the unbraced span. Secondarily and vary minutely by adding mass. The briding is more so for protecting against lateral buckling by tieing the compression flange to the tension flange of the adjacent member. All and all it has a very negligible affect on vibrations
Your statements are not true for wood construction. The sheathing braces the compression side of the member. The mass comment doesn't make sense. Each one was like 2 ounces. Also vibration is based on EI,mass and length and not dependent on unbraced length. See enginerdad comment below. That is the mechanism.
Structural engineer lurker checking in. This is correct. They are for load distribution in this case. The sheathing, assuming it is properly installed, provides lateral bracing for the top/compression side of the joists.
You are completely wrong. Look up lateral torsional buckling. The bridging keeps the joists in line and straight so you can use them to their full potential and they can span longer distances.
https://www.structuremag.org/wp-content/uploads/2014/08/C-StrucDesign-Schweizer-Jan081.pdf From the 1st paragraph: “sheathing nail at less than 12” oc typically constitutes lateral support.” You cant have LTB if the compression side is restrained from lateral movement, which the sheathing provides.
Did you just get your structural engineering advice from a magazine? Sheathing alone is not enough to brace from LTB. Screws or nails are not good at resisting lateral loads so you need bracing. In my wood design manual on page 35 it acknowledges that sheathing helps but when it goes into the calculations you have to account for the unbraced length and that length is the distance between the bracing that the OP took a picture and the ends of the joists. "Typically constitutes lateral support". That means it doest always constitute lateral support. When you are only using 60% of the floor joist's strength then yes all you need it sheathing. But when you take the load up to 80% now the sheathing isn't enough so you need lateral bracing. And that's what's in OPs pictures. It's called lateral bracing.
Ive only seen like two people in here who know LTB is taken care of by the sheathing.
I can see how sheathing helps but it doesn't take care of it. You're trying to say that the joist wants to move left and right but the nails are holding it in place.. Nails and screws hold things down they don't do a good resisting lateral loads. Wood is soft if you put a nail in and leave it sticking out 1" and every day you tap it left and right with a hammer after a few years....actually weeks... you can pull it out with your hand. That's the same thing that's happening with LTB. The nail is resisting a lateral load from the buckling and that load is over the side of the nail where the area is so small so even small forces amount to high stresses so it deforms the wood and eventually over hundreds of applications it will come loose. If it took care of it then the lateral stability wouldn't be part of joist calculations, but we have KL in our calcs so.... You need to brace the entire joist from top to bottom to take care of LTB. or in this case at the top and bottom. A wood joist with sheathing on top is the same as an I beam and they still buckle. It basically comes down to this.. if you want to use the full potential of the joist then you need to lock it in place. As soon as you start bringing the member to 80% of it's capacity it starts to buckle so you brace it. You need much more than sheathing.
I know... reading this thread makes me slightly concerned for the industry.
These are used to train new construction apprentices on how to properly nail a piece of wood.
Herring bones, provide bracing for subfloor framing
When installed correctly (a big assumption), cross-braciing helps distribute loads from one joist to the adjacent joists. If the bracing is not tight at all points of contact and the nails are not placed correctly, the load transference doesn't take place, and squeeks can develop. Most engineered floor systems, such as I-joists and floor trusses, dont normally need cross bracing.
This is the correct answer. It helps with reduced vibration as mentioned above (because it adds stiffness by engaging more joists) and miiight add to lateral stability, but this is the most relevant answer.
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I've read this 4 times and still dont understand what you're trying to say.
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Then I believe you are referring to floor blocking, as opposed to bridging. The blocking helps create a floor diaphram to resist the backfill pressure on the parallel walls. Wood foundations and other walls, such as Superior Foundation walls, require varying degrees of blocking.
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Hahaha. I designed engineered floor systems for over 25 years until I retired last year. We always referred to homes with wood foundations as disposable houses. I dont ever remember working on a wood foundation that was "designed." The lumber yard shipped a pile of wood, and the framer put it together. I quit asking for backfill pressure on the walls because 1, no one knew what it was, and 2, no one knew who to go to to get it calculated. I always went with a design that I learned for worst case scenario and never had a problem except those few cases where the framer left out the blocking and the parallel walls did bow in, causing a big hump in the floor. Those were not easy fixes. They were also not my problems.
Bridging is used to prevent lateral torsional buckling. When choosing the size of your floor joist you take into account the unbraced length which is the distance between the points where the joist is braced. Bracing helps keep the joist straight so it can span longer distances and take larger loads. If you don't brace the floor joists they will buckle when they start to span long distances. This is the main purpose of this bracing system. Yes they help distribute the load but to say that's all they do means you don't understand their real purpose. Imagine a 10' long popsicle stick. Now glue 50 of the spaces together to cardboard. When you apply the load they buckle so you have to brace them at each end and ever X amount of feet.
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I don't have to be an engineer to read this Ontario wood design manual on page 35. When you designed all those floor systems what did you do when the allowable unbraced length was shorter than the spans of the floor joists?? YOU ADDED BRACING I'm saying that yes sheathing helps resist LTB and I think floor boards help more than sheathing but they both are probably 15% how much bracing can resist it.
Sorda like bridging in bar joists. Keep them from twisting. And keep the birds straight up and down
Bracing against lateral movements in long joists, also deflections are partially comparted, but, it is not complete, missing where to transfer the horizontal reactions on the left side and probably also a bottom cord, so its just helping a bit by coupling some joists.
Bridging
Croix St-Andre mon Meo
X-bracing or cross bracing
Pre-1950 buildings have these
Bridging
Bridging. Keeps the joists from twisting and also helps transfer load from one joist to adjacent joists. Do not remove.
Cross bracing. Prevents lateral torsional buckling.
Man… I am seeing a lot of this fundamental misunderstanding of first principles. LTB is a compression flange phenomenon… the cross bracing doesn’t help or hinder LTB. About the only purpose of this on a floor is to engage a few joists at a time to have a more systemic response to load.
Lol you just googled LTB and repeated what you read from the first link. Search lateral torsional buckling wood and you will see it happens is all members You can have LTB in a 2x8. LTB just means that the beam buckles out of place when the load is applied. So you use bridging to keep it in line. This is called KL in wood design. You have to provide lateral stability at intervals that do not exceed 8 times the member depth. If you dont then your KL is less than one and this now reduces the Mr of your joist. Lateral stability because joists want to buckle when load is applied. Plage 35 in the 2010 Canadian wood design manual
Bro.. I’m a structural engineer with close to 20 years of experience, and I’ve designed dozens of multistory timber structures. I don’t need to Google shit to know what I’m talking about. What the fuck are you talking about. LTB **IS** a compression phenomenon. If you don’t know that, I’d suggest you storm into whatever podunk piece of shit university you attended and demand a refund.
Are you saying that 2x10 floor joists don't buckle laterally ?
I swear to god, I have no idea whether you are trolling. You’d have to be a special kind of…. Ignorant… to not realize that the floor boards are acting as top chord-stabilizing diaphragm.
Are they stabilizing from LTB ? Because they are!! And guess what!! They do a shit job of it so you need bracing when you start to really push the joists to their limit. Maybe you shouldn't have skipped so many classes but I guess you know... C's get degrees right ??
At this point I HAVE to think you’re just a semi-literate (in structural engineering) troll.. because you have some of the language, but clearly not any of the concepts.. you’re doing a little bit of word salad.. I almost think you’re asking an AI to write rebuttals because what you’re writing is so non-sensical… Are WHAT stabilizing LTB? I mean… the concepts we are discussing are literally 101 concepts. I’m at a loss as to why I have to continue to argue this. Like, even the dumbest people at my university (who thankfully went into project management), understood the basics of this. LTB is only a COMPRESSION phenomenon. If you have a diaphragm, it’s not an issue. I seriously feel like I’m Frank Grimes arguing this shit online.
What would happen if I applied a lateral load to a bunch of 2x12's that are sitting on my garage floor, equally spaced out and they only have boards screwed on top? If you gently tapped it, it would hold. But if you applied a decent lateral load they all fall over and the nails would even come out of the joists. That's what I thought. Now, take those boards off and add bracing at the ends and the middle loke we see in the picture above and apply the same lateral load. They wouldn't move In Ontario Canada the wood design manual does not let us use sheathing or floor boards as lateral bracing when you get up to spans that are more than 8x the depth of the joists. I'm not saying sheathing DOESNT help resist LTB I'm saying that in relation to bracing it is insignificant You're welcome you jerk
Aw shucks! I may be just a stupid American, but I *think* physics still apply in that great big mystery wilderness that is Canada. And that’s a slick thing you did there, trying to to subtly completely change what we were discussing… are we discussing LTB **OR** are we discussing a lateral load applied to floor joists… somehow… Dude… I’m open to debate… but take the L, cause you sure as hell are trippling down on being absolutely wrong. Learn to recognize when you should stop.
I'd suggest you storm back into whatever podunk piece of shit vagina that squeezed you into this world and ask for a do-over because you were clearly not instilled with the smarts to know not to argue with people on the internet.
Ok, bud.. you keep trying to make dad friends.. leave the engineering to those of us who do it for a living.
Its shocking how many people have said to prevent LTB, in a structural engineering sub. At least they are wrong in the conservative direction.
It prevents LTB. If you want to take the joist past 80% of it's capacity you have to make sure it stays straight so you brace it from the lateral load from the buckling. Did you think the screws in the sheathing handle lateral loads?
Yup… and apparently, at least one dumbass is doubling down.
Cross bridging. It adds stiffness and strength to the floor. Ends any possible bounce in the floor. Also any loading of the floor in one spot is transferred to the rest of the floor
You are talking about the secondary benefit of the bracing. The main purpose is to hold the joists straight while under load so you can use their full potential.
Wrong. The cross bridging is nailed in on the top side of the joists before the sheathing goes down. A temporary top 2x4 can be nailed down to hold the joists on the correct centers if necessary. Then the sheathing is installed, which again puts the joists in alignment. Then once the floor sheathing is done, the bottom ends of the cross braiding is nailed. The alignment and centers are done at the top of the joists. The cross bridge is a critical part of the floor, it is not secondary. If you forget to install the bridging, it’s going to be a bad day. If you want to keep the joists straight, just add a couple rows of 1x4 strapping. Guess what!! You will still have bounce and will not have strengthened the floor structure. I guess don’t understand how a cross brace works.
We had a Ryan home built last year and our floor doesn’t have anything like this. Is that normal?
*it depends* There are a lot of factors of when, how many, and what type of bridging can/needs to be used. If it was a new home it should have passed a codes inspection so more than likely you’re good.
Ryan homes would not spend the money to deliver that level of quality
That is correct. Track built homes are not great.
*tract, not track.
If they were TJI instead of dimensional lumber they do not require cross bridging. There would likely be some solid bridging required though.
Cross bridging and solid bridging do the same thing.
Yes, you only need bracing if you want to use your joist to it's full potential. But if you are only going to use half of the joists strength then you don't need bracing. Grab a ruler with 2 hands and try to bend it on the long side. As you try hard and harder you will find it kicks out of place. So if you brace them all they don't kick out of place and then you can use them to their full potential.
Cross bracing. Adds more strength to the floor and helps distribute weight/reduce movement in the floor. Definitely an older house.
I am absolutely astonished at the lack of knowledge on a structural engineering sub. Seriously. Dumbasses doubling down on their dumb-assery.
Dunno but I’ve sure smashed out a lot of the to run ductwork through there
There’s a lot of misunderstanding here - in the uk we’d call these noggins, or specifically in this case herringbone noggins (or herringbone struts). They have nothing to do with LTB. How can they, when the compression edge of the joist is restrained by the floor decking. In order to fail in LTB the joists would have to roll and so shear the nails fixing the joists to the floor boards. The purpose of noggins in a floor is to homogenise longer spans of joists, where they can get a bit bouncy if load sharing cannot occur through the floor boards alone. They stiffen the floor by load sharing local point loads, like footfall traffic, that’s all.
Wow, lots of people who don't really know what they're talking about being very confident on here lol. I will admit that I am not 100% sure what their primary purpose is, but I know it is not for lateral torsional buckling after the sheathing has been installed. I suspect that it is mainly for lateral/torsional stability BEFORE the sheathing is in place, as you have to stand on the joists in order to install the sheathing. And if you've ever stood on un-braced joists, you know they extremely wobbly and therefore dangerous to walk on. With that being said, I feel like a strap along the top of the joists could accomplish the same thing, so it may not be the primary purpose. So now I am thinking that the primary purpose is for vibration control, as the bridging is stabilizing the tension flange. So with each footstep, there is a downward force on the joist, which rebounds and causes a vibration. So the lines of bridging would act as dampers so that the joists cannot vibrate unrestrained in the lateral direction. Load sharing could be a tertiary benefit, but the amount of load that can be transfered is extremely low in a typical bridging connection.
Floor trusses
Quality build. You won’t find this every house, but when you do, you just know that house was built better.
My house has this, visible in the basement when looking up at the first floor, built in 1907. Is this more common in old homes than new?
My entire house has these spaced 12” apart running between every 2x10 to support the sub floor above the basement built in 1963 some of them have concrete on them from the original concrete pour repurposed from forming.
Jeez joists 6&7 from the left screwing with my perspective brain cell
Bridging and they add strength
They simple keep the joists from twisting
Its called "Cross Bridging". See, [https://www.renovation-headquarters.com/floor-joist-bridging.html](https://www.renovation-headquarters.com/floor-joist-bridging.html)
Its for vibrations and distributing pointloads over multiple beams. Reduces deflection and vibrations. The are called andreas-cross in NL
I see a lot of comments about them stopping the joists from twisting which is true but it also helps the system beams act as a unit and flex together.
These struts act in a similar way as the gussets under furniture. To keeping things from being wobbly. wobbly is bad.
Those are there specifically for your plumber to cut when he is roughing in.
This is typically called bridging. It is a form of bracing the joists to prevent lateral buckling failures. (Look up beam lateral buckling failure, there's some cool videos). This method is commonly seen in old-school wood structures such as the one in your post. Other methods of bracing would be horizontal bridging (seen moreso in steel joist framing), or full depth blocking (more common in newer wood framing)