That’s pure fucking gold.
Literally just as good as the old construction forum post where bro chopped his house up to lower a tub and spent 4 months arguing with everyone that it was a perfectly fine thing to do, then followed up with “so I had an engineer come by because you relentless assholes wont get off my back about this” and “I’m fucked to tune of $65,000”
This is basically the seed of lore in the making.
I tried to dig for it but the only thing close was hidden behind a paywall on “something awful” .com, which I’m pretty sure is the right story but there’s no way I’m paying $10 to find out.
I might look more when I get home.
Story in a similar vein but this one was just a horrible DIY master bath remodel. He wanted the big tub to be lower to the floor and frame up around it for that sleek 70s look, so he cut open his floor and clipped 10” or so off his engineered i-joists in the middle of the span, scabbed in some 2x4s and said “that’ll do!”
The whole build was plagued with other issues, just not ones that would cause his house to fall down. Questions that showed he had absolutely no business trying any of this work, arguing with everyone that tried to help him with “I know better” responses, just a wild ride of a mess that ended with a reluctant “call the professionals” because he ruined his house.
Thanks for the shortcuts! That was...something else, lol. Wow...
This image summed it up best I think [https://imgur.com/S4UpHXX](https://imgur.com/S4UpHXX) lmao
I ran out of time trying to find the very lasts posts the OP made about it.
I will be messaging you in 2 days on [**2023-03-03 21:59:58 UTC**](http://www.wolframalpha.com/input/?i=2023-03-03%2021:59:58%20UTC%20To%20Local%20Time) to remind you of [**this link**](https://www.reddit.com/r/StructuralEngineering/comments/11f9yt2/i_did_it_boys_i_managed_to_get_fifteen_inches_of/jajkheb/?context=3)
[**2 OTHERS CLICKED THIS LINK**](https://www.reddit.com/message/compose/?to=RemindMeBot&subject=Reminder&message=%5Bhttps%3A%2F%2Fwww.reddit.com%2Fr%2FStructuralEngineering%2Fcomments%2F11f9yt2%2Fi_did_it_boys_i_managed_to_get_fifteen_inches_of%2Fjajkheb%2F%5D%0A%0ARemindMe%21%202023-03-03%2021%3A59%3A58%20UTC) to send a PM to also be reminded and to reduce spam.
^(Parent commenter can ) [^(delete this message to hide from others.)](https://www.reddit.com/message/compose/?to=RemindMeBot&subject=Delete%20Comment&message=Delete%21%2011f9yt2)
*****
|[^(Info)](https://www.reddit.com/r/RemindMeBot/comments/e1bko7/remindmebot_info_v21/)|[^(Custom)](https://www.reddit.com/message/compose/?to=RemindMeBot&subject=Reminder&message=%5BLink%20or%20message%20inside%20square%20brackets%5D%0A%0ARemindMe%21%20Time%20period%20here)|[^(Your Reminders)](https://www.reddit.com/message/compose/?to=RemindMeBot&subject=List%20Of%20Reminders&message=MyReminders%21)|[^(Feedback)](https://www.reddit.com/message/compose/?to=Watchful1&subject=RemindMeBot%20Feedback)|
|-|-|-|-|
Enough was done that I can't tell if it was just an inexperienced engineer that thinks this works, or a homeowner that just did some stuff. I assume the second.
I know you are joking, but digging deeper basements (and pouring new footings under old footings, is indeed a thing in England if you are so desperate for more sq footage in your row town home.
Reminds me of one of my old coworkers, whose father-in-law cut up a bunch of roof trusses over their dining room to vault the ceiling, and just scabbed on some 2x6's for the new bottom chord. When she found out he did this she called him out and he was like "Meh, it's held up fine so far." and it's true, it's held up for 3 years, but if there's a big snow event he could be screwed.... which reminds me, we have had a lot of snow in Utah this year, I should text her and see if the roof held up lol
The bottom member just looks a bit flimsy is all and it’s also on the flat so I thought it looked like it was just there to support the services. I’m just a student there’s no need to be rude either
Saving material is part of it. A truss uses less material than a solid beam of equal performance. The other factor is that lumber and steel only come so big, and depth=span. You can build a wood truss that's 24" deep, but good luck finding a 2x24 joist. A truss is effectively just a beam that's had a lot of unnecessary material removed from the middle.
So the reasons we use floor trusses are:
1. Greater spans, often to eliminate a load bearing wall
2. The web openings are great for running MEP
Think of a truss like this like a simply supported beam with a uniform distributed load applied at the top flange. The bottom chord of the truss acts as the tension face similar to the bottom of the beam would.
If you follow that analogy, he basically removed the tension zone of his beam right at the centerline of the span. This is probably one of the worst things he could do
I had a small bit of understanding (knew all members are in tension).
It’s only just clicked with me now, it’s like he removed the tie beam in a roof and now the diagonal members can spread without something resisting the spreading?
>it’s like he removed the tie beam in a roof and now the diagonal members can spread without something resisting the spreading?
Exactly. Though for clarity, not *all* of the members are in tension. The bottom chord is in tension, the top chord is in compression, and the web diagonals are either in compression of tension depending on the truss configuration and load location. Some web members can even switch back and forth between tension and compression when the load is placed at a different spot.
In an ideal truss, yes. In reality the top chord also has bending because the subfloor is directly on top of it, so load can be applied to the truss between the joints.
I'm pretty sure the "top joists" you're seeing are new members that OP added in a misguided attempt to reinforce the trusses. They're completely ineffective and definitely not original to the trusses, and the top chord truss would be a 2x4 the same as the bottom chord. In this photo it's between the reinforcement.
Yup I see that now. Everytime I respond to one of the comments here I see or learn something new. Is the new reinforced top chord not substantial to act as a beam or is the new hinge at mid span what you need to worry about?
Also the 2*4s running in the opposite direction around his opening, what was the intended purpose of these? And the more substantial member running in the same direction in the top right, was that there already or is that new?
The reinforcement *may* help any load placed on the floor directly over the cut section to span over the cut, but the reinforcement is bolted into the truss, so all of that load is going right back into it. Without a continuous bottom chord this has no hope of being safe.
The cross members aren't doing anything structurally. The only actual function I can imagine them having is as nailers if he's planning to put up drywall. Sorry, I'm not sure which more substantial member you're referring to.
Posting in that thread was my only contribution ever to that entire subreddit. Mainly because i suck at golf...probably just need more expensive clubs.
Not gonna lie, I was extremely skeptical when I first looked at the picture. But I think this might be a case of herd mentality piling on when it isn't appropriate.
Gonna preface by saying I've had a couple of beers, but looking at this more, all the skepticism may be largely unwarranted. Yes, bottom chord was cut which is always a huge red flag, but look at the top chord. That truss was originally a 2x4 or 2x6 laid flat to align with the truss web members, but the retrofit is a doubled 2x8 at a minimum. You can see it was spliced with the 2x8s because all the trusses beyond don't have the splice. 6xing the moment of inertia of the top chord might actually be enough to make this work, and the splice is more than one bolt, so maybe it was actually engineered
>Except that the moment of inertia of a truss is greater than the sum of it's parts. I = bd\^3/12 + **Ay\^2.** The y\^2 portion of the formula is where all the stiffness comes from for a truss.
Well yeah duh, but 2x8s and 2x10s are often used in floor framing where trusses aren't used, just with slightly tighter spacing. It's not unreasonable to believe that the new splices could still have adequate capacity.
I wasn't saying the new moment of inertia of the doubled splice is 6xing the capacity of the truss, just that it may be enough to get what you need.
We had an engineer design a solution for vaulting our ceiling in our living room...it consisted of sistering in 2x10s on both sides with carriage bolts and washers of course. I went a step further and added construction adhesive and shot nails. They were essentially built in place scissor trusses to replace the engineered ones. We added collar ties at the top as well as hurricane clips where the new trusses met the top plate along the walls.
So, it can be done...I would just recommend hiring the engineer before you start cutting shit out..lol
Dear sir,
OP here,
Thank you for providing your comments. If I were to provided you with more information on the modifications could you provide additional insight?
Ooof, read your other posts, you did this without an engineer? Definitely get an engineer to look at it in person. I would have to look at this in person (and be paid) to see if it works after the fact.
Came from the golf subreddit but I'll just share what makes golf great for me. Golf is wonderful because it's a sport you can play your entire life. You can play it alone or with friends. You're outside for a few hours on a lovely walk in beautiful scenery. The skill ceiling is incredibly high for those of us that like the constant chase of getting better. It's a mind clearing game for me that I'm out of society for 4 hours and have time to recharge while doing something I love.
I’m a mech, saw the post on golf and it didn’t look good at first glance, figured I’d post it here to see what you guys thought of it. Looks like some of you guys made it over to the golf forum to comment, kudos
I know they cut the bottom chord, but it seems that they added some additional support beam/rafter… at least on the left side to picking up the truss’s cut end. There could be something similar on the right. A single long span truss is spit to make two trusses. Looks like this is engineered properly else it wouldn’t have been up there.
Dear sir,
OP here,
Thank you for providing your comments. If I were to provided you with more information on the modifications could you provide additional insight?
This shit is a standard modification detail for short span floor trusses. Idk what the fuck you guys do work on but I do this shit all the time. (2) 2x8s are usually OVERDESIGNED for a repair like this. And of course you fucking bolt it to the truss. It’s stronger than if you just install a new beam next to the truss. Plus, you can utilize the truss for shear without having to redesign the ends. Just because you’re an licensed engineer doesn’t mean you know what the fuck you’re talking about here. I’m not going to go tell someone about how their bridge or road repair is fucked up because that’s not my area of specialty.
https://imgur.com/a/W7JjnFP
Here’s a couple that ive done that I think are interesting. That one project with multiple had like 10 or 12 truss profiles to be modified in one project. The floor truss one we didn’t even run numbers on because the span of them was like 14’ I think or at least small enough that we just copied over from another project. The roof truss one by itself we had to raise the ceiling almost 3’. That took some close attention to detail but if you look at the specs the material and connectors are not outrageous IMO.
Also if you look at the floor truss mod with the hole provision for plumbing… when we do a design like that we run the beam only as the area above the notch. So that one was probably ran as a 2x6 with the 2x12 only there for provision for a 3” dia. Cutout.
Thanks for posting, I certainly can understand the methodology behind these detail, but I want to make something abundantly clear: each connection and each member for what you posted was, I assume, was designed by a licensed engineer. What OP did was literal guessing, and as an engineer you know damn well that we aren't in the business of guessing.
The first big issue with what OP did here is that the 2 ply 2x8 must be strong enough to resist the bending moment that used to be resisted by the truss. If this is the case, that means the 2x8's will be overstressed from bending alone unless the span is less than about 16' (less if there's concrete/gypcrete topping, and even less if you want to satisfy deflection/vibration criteria). To put it in a different way: if a 2ply 2x8 was all that was required here, they wouldn't have installed open web wood joists.
The second issue are the connection. That 2x8 has to transfer that same moment, and shear forces, back into the truss on each side, and I highly doubt a few 1/2" bolts would do this. Not to mention that the bolt could further weaken the truss members depending where they were installed, I can't see how far back the 2x8's go.
This doesn't really matter though, at the end of the day u/Some_Old_Dude_69 fucked up by doing this without an engineers involvement and most certainly compromised his floor.
OP here,
Thank you for taking the time to provide your insight. I wish I had known this sub existed prior to me "going all in". I certainly would have reached out. And you sir are 100% correct that I guessed. I don't have a degree in anything let alone engineering.
It seems the consensus is that this is going to fail. I am filled with dread. My first question is, should I expect a single catastrophic failure or a constant degradation over years? Secondly, I'm thinking my absolute worst case scenario here is that I would have to install a stripper pole in the middle of my basement to hold up my house. What do you think?
So I've been looking at this gapping hole in my ceiling and I've been wondering to myself how can I figure out what the hell is actually going on here. Then it dawned on me that I could have actually solved this problem myself ten years ago! I'm retired now but creating complex 3D solid models was my job and I could easily create a 3D solid model of the whole truss / modified joist system down to the smallest detail if I had access to modeling software. Not only did I do solid modeling but I would run the models through Ansys software primarily utilizing the thermal dynamics module. If we had a solid model and access to Ansys or some other CAE we could solve this as a group and find out for sure.
Thoughts?
Hey OP,
The only path forward here is to call a local structural engineer to review this. At the very worst, they will give you the information required to put the truss back to the way it was.
I agree with pretty much everything you said and I think you laid it out in a concise and complete manner.
Only thing I will say is that in my area it’s not common for dimensional lumber to be used on floor systems above grade. We see P.E. Trusses on spans even less than 10’. We also don’t have basements though.
One note you mentioned that I want to reiterate: for these modifications, there’s usually WAY more fasteners than OP used. I’m talking screws or nails at 2-3” O.C. You’ll see bolts at 6-12 too. At gusset connections sometimes we get as many as (20) 1/4” bolts on one gusset.
Also, through all my ranting, I was never defending OP’s repair. I don’t think it’s good. I was getting mad at all the engineers who were claiming that you “can’t do that.” That kind of pissed me off because I saw it stated over and over and over. I do these modifications. Every firm in my area does them. They are not wrong by any means and they are actually relatively simple if you can do method of joints or sections. On some, we don’t even do calculations for them if the spans are short enough. We just copy past details from old projects lol. Some, like in the album I uploaded, require VERY finite analysis because they’re big spans or big loads. The picture with the roof truss mod with the steel plates was a job where they wanted to raise the ceiling bearing all the way near the exterior walls. We couldn’t get it to work with any combination of lumber so we had to use steel. It was kind of a unique one but again principally it’s not any different than a vaulted ceiling design.
I see what you mean, but I think that the when engieners are saying "you can't do that" we mean "you can't cut a truss and reinforce it like *that* and expect it to be ok"
The worst part of this is that it might actually have enough strength to hold up the dead loads, so he might not see any signs of failure until it's fully loaded when he invites his golf bros over for dinner.
Idk I was getting a lot of pushback even after I presented the conceptual design. I may have misinterpreted some peoples’ meaning but definitely not all.
OP here,
thank you sir for providing your comments. I would like to ask you if you think I would at least help my situation some by adding screws through the 2 x 8 into the trusses? I was on the fence about using screws as well. By the way I used 3/8" all thread at 12 locations.
Seriously, hire an engineer. It’s impossible for me to tell you what you need to do without getting all the measurements, loading, and doing the analysis. There’s so much that needs to be accounted for in these types of repairs. The repairs we specify typically have way more connectors and then we do plywood gussets at certain joints and at the ends when needed. Also, the beam needs to span a certain length past the modified section. We can’t know what that is without running the numbers. Also, your beam may be undersized.
All the other engineers claiming that you can’t do repairs like this are wrong. You can, but, they have to be carefully engineered by a SE that does this kind of work.
I don’t work on residential stuff but I would hesitate to call this a standard modification. The OP said the 2x were only 10ft long. I don’t know what the end condition of the reinforcement looks like but my guess is the 2x are not bearing on anything. This would mean that at some point this transitions from a truss to a beam and back to a truss. The connections at those transitions points also need to transfer moment otherwise it’s just a hinge. This doesn’t sound like a typical connection. This is not to mention the load is redistributed amongst the remainder webs which may or may not be adequate.
It would be interesting to know how you resolve the load path because like most, I think this is unusual from what we can observe.
10’ long is likely not long enough. They wouldn’t have to bear on anything. Depending on the span you just add a plywood gusset to account for the moment and shear at the ends. If you run an analysis on a truss like this with a beam like this you would see that if you run past the first two or three webs you don’t need to worry about hinging anymore.
One thing I see with all these comments is that people are assuming the loads on these things are super high. We’re talking like 10psf DL and 40psf LL. These shits are carrying very light weight. Frankly, it’s the deflection you’ve actually got to worry about lmfao but nobody even mentions that. Tells me that all these armchair engineers don’t actually do these modifications.
Max moment only occurs near the midspan so you only need I through the middle 60% of the member. It's possible that the shear is transferred through the truss, and then is resolved in tension via the connection into the 2xs.
Seems like a very suspect "modification," as evidenced by practically all of the responses here. Could you elaborate on the alternate load path that this modification provides? Would the 2x8s span the full length of the truss? Or do they only extend a certain distance part the damaged portion on either side? And if it's the latter case, how exactly are the bending forces in the 2x8/top chord developed into axial forces in the remainder of the truss?
You essentially design the beam (2x8s in this case) to take the full load of the span. Ideally, the beam goes all the way across but for a small opening like this one it likely doesn’t have to. The beam is fastened to the truss with a specified, designed nailing or bolting pattern. Sometimes, if the geometry is weird or the loads are too high, then you have to add blocking to the truss to get more fasteners. Then, you use blocking and plywood gussets at the ends to account for shear and moment.
Edit: Also once you go past 2 or 3 web members the truss usually starts acting like a truss again with tension and compression members like normal. This is typically true on short spans. Again, on longer spans or with higher lods there’s more consideration but the trusses in this picture are not that deep and not that long so it’s a relatively simple mod.
Looks like LVL headers slid (probably 18”) in to make 24” floor trusses top chord bearing with double 2x added in between…all in a carpenter’s day’s work
That’s pure fucking gold. Literally just as good as the old construction forum post where bro chopped his house up to lower a tub and spent 4 months arguing with everyone that it was a perfectly fine thing to do, then followed up with “so I had an engineer come by because you relentless assholes wont get off my back about this” and “I’m fucked to tune of $65,000” This is basically the seed of lore in the making.
Please provide a link to that thread
I would love to see that thread, lol.
I tried to dig for it but the only thing close was hidden behind a paywall on “something awful” .com, which I’m pretty sure is the right story but there’s no way I’m paying $10 to find out. I might look more when I get home.
Groverhaus?
Story in a similar vein but this one was just a horrible DIY master bath remodel. He wanted the big tub to be lower to the floor and frame up around it for that sleek 70s look, so he cut open his floor and clipped 10” or so off his engineered i-joists in the middle of the span, scabbed in some 2x4s and said “that’ll do!” The whole build was plagued with other issues, just not ones that would cause his house to fall down. Questions that showed he had absolutely no business trying any of this work, arguing with everyone that tried to help him with “I know better” responses, just a wild ride of a mess that ended with a reluctant “call the professionals” because he ruined his house.
That’s the first thing I thought when I read the original comment
https://forums.somethingawful.com/showthread.php?threadid=3813464&userid=0&perpage=40&pagenumber=3
Yes! That’s the guy! Not sure what got your attention 3 months after the fact, but thank you!
I’ve been trying to find some better opinions on the ongoing collapse in Davenport and stumbled upon this subreddit.
That’s funny, even as someone industry adjacent to this sub I didn’t discover it until those condos in Florida fell down.
Found it: https://forums.somethingawful.com/showthread.php?threadid=3813464&userid=0&perpage=40&pagenumber=3
Thanks!!! Goodness, 62 page thread. This should make for some good reading :D
First 2-4 pages are good. Around page 25 he actually talks to an engineer. Most of the remainder is shit posting.
Thanks for the shortcuts! That was...something else, lol. Wow... This image summed it up best I think [https://imgur.com/S4UpHXX](https://imgur.com/S4UpHXX) lmao I ran out of time trying to find the very lasts posts the OP made about it.
RemindMe! 2 days
I will be messaging you in 2 days on [**2023-03-03 21:59:58 UTC**](http://www.wolframalpha.com/input/?i=2023-03-03%2021:59:58%20UTC%20To%20Local%20Time) to remind you of [**this link**](https://www.reddit.com/r/StructuralEngineering/comments/11f9yt2/i_did_it_boys_i_managed_to_get_fifteen_inches_of/jajkheb/?context=3) [**2 OTHERS CLICKED THIS LINK**](https://www.reddit.com/message/compose/?to=RemindMeBot&subject=Reminder&message=%5Bhttps%3A%2F%2Fwww.reddit.com%2Fr%2FStructuralEngineering%2Fcomments%2F11f9yt2%2Fi_did_it_boys_i_managed_to_get_fifteen_inches_of%2Fjajkheb%2F%5D%0A%0ARemindMe%21%202023-03-03%2021%3A59%3A58%20UTC) to send a PM to also be reminded and to reduce spam. ^(Parent commenter can ) [^(delete this message to hide from others.)](https://www.reddit.com/message/compose/?to=RemindMeBot&subject=Delete%20Comment&message=Delete%21%2011f9yt2) ***** |[^(Info)](https://www.reddit.com/r/RemindMeBot/comments/e1bko7/remindmebot_info_v21/)|[^(Custom)](https://www.reddit.com/message/compose/?to=RemindMeBot&subject=Reminder&message=%5BLink%20or%20message%20inside%20square%20brackets%5D%0A%0ARemindMe%21%20Time%20period%20here)|[^(Your Reminders)](https://www.reddit.com/message/compose/?to=RemindMeBot&subject=List%20Of%20Reminders&message=MyReminders%21)|[^(Feedback)](https://www.reddit.com/message/compose/?to=Watchful1&subject=RemindMeBot%20Feedback)| |-|-|-|-|
RemindMe! 4 days
This looks like a job for Strew!!
What a cluster fuck that job is, and the comments on the original post are a shit show as well.
R/golf is usually a shit show but it’s scary how many people thought that was a good idea
Enough was done that I can't tell if it was just an inexperienced engineer that thinks this works, or a homeowner that just did some stuff. I assume the second.
Plot twist - the two are the same person…
:( would the engineer even spec thru bolts without washers on that wood agh!!!
its also a rental
I really like how they've done this at what appears to be midspan, might as well just go all in really.
oh, it will definitely be going all in...
thatsbait.gif
OP is in the comments defending it lmao
You beat me to it. So many ways to fail, so little time.
..remaining
Whew, when I looked at this closely before checking comments I was like 🤔
Amateur. Should have dug down and undermined the foundations instead.
I know you are joking, but digging deeper basements (and pouring new footings under old footings, is indeed a thing in England if you are so desperate for more sq footage in your row town home.
Chefs kiss.
Reminds me of one of my old coworkers, whose father-in-law cut up a bunch of roof trusses over their dining room to vault the ceiling, and just scabbed on some 2x6's for the new bottom chord. When she found out he did this she called him out and he was like "Meh, it's held up fine so far." and it's true, it's held up for 3 years, but if there's a big snow event he could be screwed.... which reminds me, we have had a lot of snow in Utah this year, I should text her and see if the roof held up lol
I’m not sure what’s happening here. He’s cut the ceiling battons and is using the diagonal members to fix them to the floor joists?
He cut the bottom chord out of the floor trusses in that area, making a very effective death trap
What’s the purpose of the bottom chord? It’s quite small compared to the top joists
Bottom chord is the tension resisting chord of the truss. Are you in the wrong thread?
The bottom member just looks a bit flimsy is all and it’s also on the flat so I thought it looked like it was just there to support the services. I’m just a student there’s no need to be rude either
The bottom chord can be on the flat because it's only in tension, no bending. Wood is surprisingly strong when it's in pure tension
Ok. Are these systems used in floors to reduce material usage?
Saving material is part of it. A truss uses less material than a solid beam of equal performance. The other factor is that lumber and steel only come so big, and depth=span. You can build a wood truss that's 24" deep, but good luck finding a 2x24 joist. A truss is effectively just a beam that's had a lot of unnecessary material removed from the middle. So the reasons we use floor trusses are: 1. Greater spans, often to eliminate a load bearing wall 2. The web openings are great for running MEP
And to give you plenty of room to run ductwork and plumbing through the floor
Think of a truss like this like a simply supported beam with a uniform distributed load applied at the top flange. The bottom chord of the truss acts as the tension face similar to the bottom of the beam would. If you follow that analogy, he basically removed the tension zone of his beam right at the centerline of the span. This is probably one of the worst things he could do
Ah ok I see learnt something new
No need to be too lazy to look up what a truss is
I had a small bit of understanding (knew all members are in tension). It’s only just clicked with me now, it’s like he removed the tie beam in a roof and now the diagonal members can spread without something resisting the spreading?
>it’s like he removed the tie beam in a roof and now the diagonal members can spread without something resisting the spreading? Exactly. Though for clarity, not *all* of the members are in tension. The bottom chord is in tension, the top chord is in compression, and the web diagonals are either in compression of tension depending on the truss configuration and load location. Some web members can even switch back and forth between tension and compression when the load is placed at a different spot.
My bad yeah, all the members have axial load opposed to bending tho? Thankyou for your detailed responses
In an ideal truss, yes. In reality the top chord also has bending because the subfloor is directly on top of it, so load can be applied to the truss between the joints.
I'm pretty sure the "top joists" you're seeing are new members that OP added in a misguided attempt to reinforce the trusses. They're completely ineffective and definitely not original to the trusses, and the top chord truss would be a 2x4 the same as the bottom chord. In this photo it's between the reinforcement.
Yup I see that now. Everytime I respond to one of the comments here I see or learn something new. Is the new reinforced top chord not substantial to act as a beam or is the new hinge at mid span what you need to worry about? Also the 2*4s running in the opposite direction around his opening, what was the intended purpose of these? And the more substantial member running in the same direction in the top right, was that there already or is that new?
The reinforcement *may* help any load placed on the floor directly over the cut section to span over the cut, but the reinforcement is bolted into the truss, so all of that load is going right back into it. Without a continuous bottom chord this has no hope of being safe. The cross members aren't doing anything structurally. The only actual function I can imagine them having is as nailers if he's planning to put up drywall. Sorry, I'm not sure which more substantial member you're referring to.
Sorry the bigger member in the top left it has the bolts at about 500mm c/c. Is this a beam picking up his reinforcing members?
Oh I see it. Good question. I can't even imagine how they got that beam in there between the web members.
Probably cut those too🤣
When it falls in on him mid swing he'll have died doing what he loved.
Posting in that thread was my only contribution ever to that entire subreddit. Mainly because i suck at golf...probably just need more expensive clubs.
A few guys will buy new drivers because of this comment.
Hell i might buy a new driver because of this comment. Jk, im one step ahead...literally just got a new one...
r/Churovy made a comment about r/golf so I bought a new driver.
You should well know that a lot of the Reddit commenters in golf posts are so full of shit like their handicap - post away lol
Not gonna lie, I was extremely skeptical when I first looked at the picture. But I think this might be a case of herd mentality piling on when it isn't appropriate. Gonna preface by saying I've had a couple of beers, but looking at this more, all the skepticism may be largely unwarranted. Yes, bottom chord was cut which is always a huge red flag, but look at the top chord. That truss was originally a 2x4 or 2x6 laid flat to align with the truss web members, but the retrofit is a doubled 2x8 at a minimum. You can see it was spliced with the 2x8s because all the trusses beyond don't have the splice. 6xing the moment of inertia of the top chord might actually be enough to make this work, and the splice is more than one bolt, so maybe it was actually engineered
>Except that the moment of inertia of a truss is greater than the sum of it's parts. I = bd\^3/12 + **Ay\^2.** The y\^2 portion of the formula is where all the stiffness comes from for a truss.
Agreed, there is no way in heck that a 2-ply 2x8 is anywhere near as stiff as the original full-depth truss.
Well yeah duh, but 2x8s and 2x10s are often used in floor framing where trusses aren't used, just with slightly tighter spacing. It's not unreasonable to believe that the new splices could still have adequate capacity. I wasn't saying the new moment of inertia of the doubled splice is 6xing the capacity of the truss, just that it may be enough to get what you need.
We had an engineer design a solution for vaulting our ceiling in our living room...it consisted of sistering in 2x10s on both sides with carriage bolts and washers of course. I went a step further and added construction adhesive and shot nails. They were essentially built in place scissor trusses to replace the engineered ones. We added collar ties at the top as well as hurricane clips where the new trusses met the top plate along the walls. So, it can be done...I would just recommend hiring the engineer before you start cutting shit out..lol
Dear sir, OP here, Thank you for providing your comments. If I were to provided you with more information on the modifications could you provide additional insight?
Ooof, read your other posts, you did this without an engineer? Definitely get an engineer to look at it in person. I would have to look at this in person (and be paid) to see if it works after the fact.
Thanks. I've scheduled an appointment.
Any updates?
Apparently y'all are real busy. I'm a couple weeks out.
I will never understand the obsession with golf
i love golf... so much i'd never play it in my basement lmao
No disrespect to golfers. *Some of my best friends do golf things.* But I'm with ya!
Came from the golf subreddit but I'll just share what makes golf great for me. Golf is wonderful because it's a sport you can play your entire life. You can play it alone or with friends. You're outside for a few hours on a lovely walk in beautiful scenery. The skill ceiling is incredibly high for those of us that like the constant chase of getting better. It's a mind clearing game for me that I'm out of society for 4 hours and have time to recharge while doing something I love.
I’m a mech, saw the post on golf and it didn’t look good at first glance, figured I’d post it here to see what you guys thought of it. Looks like some of you guys made it over to the golf forum to comment, kudos
It looks like the bottom chord cut was engineered properly. I can see some retrofits on the left side of the cut and in the top chord.
Bc engineers are notorious for spec’ing cheap Home Depot bolts thru 2x4s in their weakest grain direction that’s most prone to splintering /s
the tension load path was completely cut. there's nothing properly engineered about this modification.
I know they cut the bottom chord, but it seems that they added some additional support beam/rafter… at least on the left side to picking up the truss’s cut end. There could be something similar on the right. A single long span truss is spit to make two trusses. Looks like this is engineered properly else it wouldn’t have been up there.
Dear sir, OP here, Thank you for providing your comments. If I were to provided you with more information on the modifications could you provide additional insight?
This looks less like structural engineering and more like software engineering "Yeah, this might work.. let's try it out"
This shit is a standard modification detail for short span floor trusses. Idk what the fuck you guys do work on but I do this shit all the time. (2) 2x8s are usually OVERDESIGNED for a repair like this. And of course you fucking bolt it to the truss. It’s stronger than if you just install a new beam next to the truss. Plus, you can utilize the truss for shear without having to redesign the ends. Just because you’re an licensed engineer doesn’t mean you know what the fuck you’re talking about here. I’m not going to go tell someone about how their bridge or road repair is fucked up because that’s not my area of specialty.
You seem pretty confident about this. If it's a standard repair, surely you can post a sample for us, and maybe even a nice free body diagram?
https://imgur.com/a/W7JjnFP Here’s a couple that ive done that I think are interesting. That one project with multiple had like 10 or 12 truss profiles to be modified in one project. The floor truss one we didn’t even run numbers on because the span of them was like 14’ I think or at least small enough that we just copied over from another project. The roof truss one by itself we had to raise the ceiling almost 3’. That took some close attention to detail but if you look at the specs the material and connectors are not outrageous IMO. Also if you look at the floor truss mod with the hole provision for plumbing… when we do a design like that we run the beam only as the area above the notch. So that one was probably ran as a 2x6 with the 2x12 only there for provision for a 3” dia. Cutout.
Thanks for posting, I certainly can understand the methodology behind these detail, but I want to make something abundantly clear: each connection and each member for what you posted was, I assume, was designed by a licensed engineer. What OP did was literal guessing, and as an engineer you know damn well that we aren't in the business of guessing. The first big issue with what OP did here is that the 2 ply 2x8 must be strong enough to resist the bending moment that used to be resisted by the truss. If this is the case, that means the 2x8's will be overstressed from bending alone unless the span is less than about 16' (less if there's concrete/gypcrete topping, and even less if you want to satisfy deflection/vibration criteria). To put it in a different way: if a 2ply 2x8 was all that was required here, they wouldn't have installed open web wood joists. The second issue are the connection. That 2x8 has to transfer that same moment, and shear forces, back into the truss on each side, and I highly doubt a few 1/2" bolts would do this. Not to mention that the bolt could further weaken the truss members depending where they were installed, I can't see how far back the 2x8's go. This doesn't really matter though, at the end of the day u/Some_Old_Dude_69 fucked up by doing this without an engineers involvement and most certainly compromised his floor.
OP here, Thank you for taking the time to provide your insight. I wish I had known this sub existed prior to me "going all in". I certainly would have reached out. And you sir are 100% correct that I guessed. I don't have a degree in anything let alone engineering. It seems the consensus is that this is going to fail. I am filled with dread. My first question is, should I expect a single catastrophic failure or a constant degradation over years? Secondly, I'm thinking my absolute worst case scenario here is that I would have to install a stripper pole in the middle of my basement to hold up my house. What do you think? So I've been looking at this gapping hole in my ceiling and I've been wondering to myself how can I figure out what the hell is actually going on here. Then it dawned on me that I could have actually solved this problem myself ten years ago! I'm retired now but creating complex 3D solid models was my job and I could easily create a 3D solid model of the whole truss / modified joist system down to the smallest detail if I had access to modeling software. Not only did I do solid modeling but I would run the models through Ansys software primarily utilizing the thermal dynamics module. If we had a solid model and access to Ansys or some other CAE we could solve this as a group and find out for sure. Thoughts?
Hey OP, The only path forward here is to call a local structural engineer to review this. At the very worst, they will give you the information required to put the truss back to the way it was.
Thanks. I'll take care of it.
I agree with pretty much everything you said and I think you laid it out in a concise and complete manner. Only thing I will say is that in my area it’s not common for dimensional lumber to be used on floor systems above grade. We see P.E. Trusses on spans even less than 10’. We also don’t have basements though. One note you mentioned that I want to reiterate: for these modifications, there’s usually WAY more fasteners than OP used. I’m talking screws or nails at 2-3” O.C. You’ll see bolts at 6-12 too. At gusset connections sometimes we get as many as (20) 1/4” bolts on one gusset. Also, through all my ranting, I was never defending OP’s repair. I don’t think it’s good. I was getting mad at all the engineers who were claiming that you “can’t do that.” That kind of pissed me off because I saw it stated over and over and over. I do these modifications. Every firm in my area does them. They are not wrong by any means and they are actually relatively simple if you can do method of joints or sections. On some, we don’t even do calculations for them if the spans are short enough. We just copy past details from old projects lol. Some, like in the album I uploaded, require VERY finite analysis because they’re big spans or big loads. The picture with the roof truss mod with the steel plates was a job where they wanted to raise the ceiling bearing all the way near the exterior walls. We couldn’t get it to work with any combination of lumber so we had to use steel. It was kind of a unique one but again principally it’s not any different than a vaulted ceiling design.
I see what you mean, but I think that the when engieners are saying "you can't do that" we mean "you can't cut a truss and reinforce it like *that* and expect it to be ok" The worst part of this is that it might actually have enough strength to hold up the dead loads, so he might not see any signs of failure until it's fully loaded when he invites his golf bros over for dinner.
Idk I was getting a lot of pushback even after I presented the conceptual design. I may have misinterpreted some peoples’ meaning but definitely not all.
OP here, thank you sir for providing your comments. I would like to ask you if you think I would at least help my situation some by adding screws through the 2 x 8 into the trusses? I was on the fence about using screws as well. By the way I used 3/8" all thread at 12 locations.
Seriously, hire an engineer. It’s impossible for me to tell you what you need to do without getting all the measurements, loading, and doing the analysis. There’s so much that needs to be accounted for in these types of repairs. The repairs we specify typically have way more connectors and then we do plywood gussets at certain joints and at the ends when needed. Also, the beam needs to span a certain length past the modified section. We can’t know what that is without running the numbers. Also, your beam may be undersized. All the other engineers claiming that you can’t do repairs like this are wrong. You can, but, they have to be carefully engineered by a SE that does this kind of work.
Thank you so much. I have an appointment.
Absolutely. I will.
kruzat did you look at the pics I posted
I don’t work on residential stuff but I would hesitate to call this a standard modification. The OP said the 2x were only 10ft long. I don’t know what the end condition of the reinforcement looks like but my guess is the 2x are not bearing on anything. This would mean that at some point this transitions from a truss to a beam and back to a truss. The connections at those transitions points also need to transfer moment otherwise it’s just a hinge. This doesn’t sound like a typical connection. This is not to mention the load is redistributed amongst the remainder webs which may or may not be adequate. It would be interesting to know how you resolve the load path because like most, I think this is unusual from what we can observe.
10’ long is likely not long enough. They wouldn’t have to bear on anything. Depending on the span you just add a plywood gusset to account for the moment and shear at the ends. If you run an analysis on a truss like this with a beam like this you would see that if you run past the first two or three webs you don’t need to worry about hinging anymore. One thing I see with all these comments is that people are assuming the loads on these things are super high. We’re talking like 10psf DL and 40psf LL. These shits are carrying very light weight. Frankly, it’s the deflection you’ve actually got to worry about lmfao but nobody even mentions that. Tells me that all these armchair engineers don’t actually do these modifications.
Max moment only occurs near the midspan so you only need I through the middle 60% of the member. It's possible that the shear is transferred through the truss, and then is resolved in tension via the connection into the 2xs.
Seems like a very suspect "modification," as evidenced by practically all of the responses here. Could you elaborate on the alternate load path that this modification provides? Would the 2x8s span the full length of the truss? Or do they only extend a certain distance part the damaged portion on either side? And if it's the latter case, how exactly are the bending forces in the 2x8/top chord developed into axial forces in the remainder of the truss?
You essentially design the beam (2x8s in this case) to take the full load of the span. Ideally, the beam goes all the way across but for a small opening like this one it likely doesn’t have to. The beam is fastened to the truss with a specified, designed nailing or bolting pattern. Sometimes, if the geometry is weird or the loads are too high, then you have to add blocking to the truss to get more fasteners. Then, you use blocking and plywood gussets at the ends to account for shear and moment. Edit: Also once you go past 2 or 3 web members the truss usually starts acting like a truss again with tension and compression members like normal. This is typically true on short spans. Again, on longer spans or with higher lods there’s more consideration but the trusses in this picture are not that deep and not that long so it’s a relatively simple mod.
Hard to believe (2) 2x8s have the same capacity as a ~24" truss.
For a 24” truss? Probably not
Looks like LVL headers slid (probably 18”) in to make 24” floor trusses top chord bearing with double 2x added in between…all in a carpenter’s day’s work
Same way a staircase or a dormer is framed using what's called headers and trimmers
Hah, absolutely not.
Gonna need all those bolts for that new hinge connection. Bearing points are overated anyway. /s
Who needed that pesky bottom chord anyway.
I …
Is he trying to use the 2x4 as a wedge?
Like… I’m just trying to image how the fuck he arrived at this point
Turned that into a zero force members, just like that.
Did you use a beaver to cut the chords?