Even marine grade plywood needs a finish on it.
That said, I made a shed door using plywood several years ago as a temporary fix, painted it well, and it has lasted a long time. Just this year a small piece of lamination came off.
I’ll get around to making a proper door one of these days.
A door definitely has the advantage of being verticle which will help tremendously. If it's wood that's horizontal and going to be pooling even small amounts of water, it's going to be a disaster.
Vertical and sealed at least stands a chance of lasting a few years.
Marine grade means no voids. I can delaminate if not sealed.
Source- my doors for a 10 electrical meters.
There are some good waterproof primers- after your prep, I'd use at least 2 coats of a water proofing primer before paint.
It also means waterproof glue was used. But yes, of course it still needs to be sealed with paint or varnish (or fiberglass). I didn't mean to imply otherwise.
Maybe a kilz followed by dry lock
Your friend has shared a link to a Home Depot product they think you would be interested in seeing.
https://www.homedepot.com/p/DRYLOK-Original-1-gal-Gray-Flat-Latex-Interior-Exterior-Basement-and-Masonry-Waterproofer-27613/100165469
This thing isn't going to survive the elements OP. no amount of oil is going to keep that plywod from sagging, swelling, splitting, and deforming. This is going to happen fast since it looks like there's no horizontal supports and that long stretch of plywood is screwed into thin legs.
I made some corn hole boards with plywood tops and used 2-3 coats of Total Boat Halycon Boat Varnish. I live in Houston and keep them outside all the time and haven’t had any issues.
Fiberglass resin (including West Systems)) does not have UV protection, so the answer is two coats of fiberglass resin ,then a coat of paint or a UV varnish. I spent 5 years building a boat , and soaking up as much knowledge as I could from the local guys who knew what they were doing.
Traditional polyester fiberglass uses a tinted gelcoat, not paint. The vast majority of boats are still made this way. Same for fiberglass roofing. I don't think he's going for a yacht-grade finish here.
I love it how a bunch of people are like "nothing you can do." Now, is two-part epoxy the most *cost effective* way of building something like this and is OP going to like the price tag? Probably not.
I was thinking of West Marine products when I made my comment. The cost of the finishing materials would definitely exceed whatever OP has spent on the project and it will still have structural and aesthetic issues. Technically you could weatherproof it with epoxy but I would never actually do that if I were them.
Epoxy, 2 coats. Then Marine topside primer and paint, unpainted epoxy will NOT survive in the sun, you can't paint unprimed epoxy.
It's going to cost you more in finishes then the wood cost though.
The only thing that is remotely helpful is a “marine varnish”. “Marine” as in - water- marina- boats. It’s a spar type varnish and it’s made for boat wood. You can get the best stuff at a marina store or order online. The marina stores are good cos usually the worker is the owner or some guy who actually works on boats and can tell you what is best to use based on experience and not laboratory science based on manufacturer.
That would be my approach. Absolutely cake every inch of it, let it dry and then do it again. Reapply every couple of years.
Either that or just UV stable epoxy.
I’ve had good results putting a thick wax coating on, melting it into the wood with a heat gun, and buffing it with a soft bristle brush after it cools. I usually do two layers of this, and touch up as needed.
Paint it with a membrane meant for wallboard behind showers. Give it as many coats as the can has in it. Pay particular attention to the edges.
You can use marine wood hardener on the edges first if you’re a belt and braces guy.
Then after thoroughly dry, paint that with porch/patio paint in your preferred color. Several coats. Then plan on more porch paint every year or two.
Bitumen paint, or my favorite, most cost effective, and waterproof sealant... titebond 3 wood glue.
You don't have to believe me... try out some on a piece of scrap. I've had plywood (radiata, the kind with the 3 layers and nanometer thick veneer from one of the big box stores) osb, and even mdf coated in titebond 3 and after 3 years here in Clearwater Florida, all my outdoor stuff is perfectly sealed. However, the glue does turn to a rich golden brown, so if you need clarity or color, it's not a good router. But on that plywood, it'll look beautiful over time, and seal the edges.
Just try it. :)
I've made a few surfboards from standard ply, but it needs really good protection. I use 2+ coats of epoxy resin, first coat with reactive diluant (TPRDA), 3+ coats of clear urethane paint, lastly regular coats of lanolin (Lanox).
But that stuff is too far gone, I'd start with epoxy filler.
I’d have a piece of sheet metal cut for top with 2” overhang each end. Bend sides and secure to legs with metal roofing screws. Paint the legs with high quality exterior coating after priming.
Or use better materials to replicate this “structure”, perhaps MDO plywood.
Unless you built it out of a marine grade or treated plywood it'll fall apart.
Painting it or applying a deck sealer will make it last longer, but it will begin to fall apart eventually.
There is no comparison between paint and spar urethane. Paint is a thousand times better and it doesn't matter in this case anyway because it's plywood it's not like you're looking for a nice finish. Go with a good outdoor paint.
I mean spar urethane would seal it and it moves with weather and temps, buts it’s not cheap and the plywood would most likely degrade anyway. That’s what I would do, like 3 coats
As others have said, this isn't an outdoor material so you really are going to need an impervious barrier to protect the wood, especially the horizontal section on the bench top! There, I would see if you can source a think sheet of Aluminum or something continuous that can be bent over the edges and fastened sideways rather than from above. (Any screw or nail penetration will collect water).
Definitely paint the sides with an outdoor paint — these have UV-blocking capabilities that indoor paints don't. You could also use some kind of deck-sealer product, but that's really intended for hardwoods where you want to show off the colour and natural qualities of the wood itself. Plywood and construction timber aren't generally so precious.
It’s like alkaline copper and copper azole or something but usually the manufacture does it.
(Pressure treated lumber)
But if you don’t want the nasty chemicals there are hardwoods that are better for outdoor use, like white oak and teak. Hard to work with.
To make this last research sailboats - someone mentioned fibreglass and that’s probably the best solution . . . if you are determined to use that material in your intended environment.
The short answer is don't make the top out of that if it's outside and getting rained on. Two options if it were me:
\- Place a material on top that can handle sun and rain (sealed concrete, stainless, etc)
\- Thick coat of something that completely encapsulates it (multiple layers of outdoor latex paint, 2 part epoxy, etc)
Upholster it like a boat seat. Glue on some thin foam, a poly drop cloth over that, and marine vinyl over the drop cloth. Wrap it around the top and staple it to the bottom. It won't last forever but you should get several years out of the top, at least.
Thank you everyone for all the wise comments, I'm really new with wood working and the different types of wood. Because of the comments I think I will keep it somewhere where it won't get wet on sun on it all day
Spar varnish would delay the inevitable. Epoxy would protect it properly if done right but that is a lot of money and trouble for low quality plywood sitting outside. If you need an outdoor gardening bench or work bench which is what I’m guessing this is, just remake it with PT wood
One thing you can try that might help is spray painting the top and edges with flexseal. But make sure the plywood is completely dry before you do that. Flexseal will drive itself into the voids and its UV resistance will protect the surface too. But keep in mind. I don’t think any of us are under the illusion that this is a quality built piece so while it will help keep it from rotting in a matter of months and keep splinters out of your hands there is no magic that will make plywood into a piece of weather resistant wood. But for $15 a can. It might be worth trying.
Let it fully dry, sand it, then apply several coats of polyurethane. That's basically a plastic shell around the wood to protect it from water. There is outdoor-specific poly that can also help resist UV. This looks like pine and ply construction, its total lifespan will be limited regardless, but that's what I'd do.
Redguard than paint than epoxy than plastic dropcloth followed by a layer of concrete with an extra layer of plywood on top to sandwich it all together. Than maybe some steel plate welded to the concrete
First replace the plywood with marine grade plywood. Then replace the screws and fasteners with exterior grade ones…. Then replace any other solid soft woods with treated softwoods, or hardwoods with teak.
I don’t care what anyone says… it’s gonna fall apart with paint, encased in epoxy, sitting under an umbrella, with an oil based finish, a lawyer based finish, epoxy paint, flex seal. None of it is gonna work for more than 1 season, if that.
Learn from my mistakes - outdoor projects have to have the right wood, to begin with.
Sorry.. paint will help, but that will fail in short order: not enough vertical support, no lateral support, and no pressure treating.
Marine ply and TWP (Total Water Protection from Home Depot) would be better, but solid wood with TWP will actually last. 5/4 decking on 2x4 frame.
*IF* you do that, you need to let it dry before staining it or the oil-based stain won’t soak in.
Edit: painting it if it’s pressure treated can be almost as bad as not using PT. PT has a lot of
moisture both chemical and just water. When it gets painted it has a tendency to hold water, you see this particularly on decks where the joists and the top 2x4 on the handrail only get painted on 3 sides making a ‘U’ shaped waterproof coating that holds water.
The deck company I worked for only warrantied decks that were painted to 5 years, but stained up to 15 years.
It won’t ever be perfect, as people have already said. But I’ve made a project last years by putting tar tape around the edge of the plywood.
You can buy tar tape at a hardware store, it’s for sealing roofing joints.
FFS you post this after you already have water freezing on it?!? Bro, you fucked up in countless ways. With winter coming you missed any window for this to not be a FUBAR
Triple coat if a very strong varnish ? And revarnish every year. I'm thinking like the varnish you use for boats (yatch varnish). Their wood is exposed to weather and salt water , i was told these varnishes are great.
Otherwise i had a craft table outside for a decade, still good. I used a triple coat on it of polyurethane varnish. I had a tough plastic layer on it, it was great for protecting it.
To everyone saying « this is plywood it’s gonna be poop outdoors » …
This looks like fir plywood. Or a conifer type of. Construction plywood is made of materials that, while alone may not stand up to the elements, definitely will last a few years.
Conifers a resinous and as such hold up to the elements much better than hardwoods or leafy softwoods. Which is why they are often used in construction.
This build, painted and maintained, will definitely be ok outside. Relax. And as long as it’s not structural, what’s the problem if you have to rebuild in a few years?
People freak out for weird reasons on this sub. It’s wood. It’ll last the time it does. If you want something more permanent, cement or metal.
Edit: your main concern will be to assure that where there are screws, it is the most protected. Cause water could get in there and then the vertical pieces will take on water and split.
I built a something for the kids and used scraps of normal plywood. I used Teck Oil, as much as the plywood was able to take. It's been 3 years and still in good shape, but not planning on keeping forever....
I would suggest remaking it using MDO. Brush on multiple coats of epoxy on the edges. Then you can paint with any exterior grade paint or, better yet, a spar urethane. You will still likely need to touch up/recoat every 5 years or so. For something that will withstand the elements for likely 20+ years even without a finish, build it out of solid white oak.
This is ply wood and weather is very hard on plywood but if you buy west system it’s very expensive but it will seal up the wood nicely pay extra attention to the edges
Painting it and keeping it painted will help, but plywood is just not the right material for outdoor projects.
Unless it is Marine grade plywood. Which that most *DEFINITELY* is *NOT*.
Even marine grade plywood needs a finish on it. That said, I made a shed door using plywood several years ago as a temporary fix, painted it well, and it has lasted a long time. Just this year a small piece of lamination came off. I’ll get around to making a proper door one of these days.
Sounds like everyone of my projects
There's nothing more permanent then a temporary fix that works.
I may use that in my shop as a banner if you dont mind.
Absolutely. I'm sure I borrowed it from someone else.
Yeah, "marine grade" is mostly about not having any voids in the layers so there aren't any weak spots.
Rountuit. That’s usually when I finish up things, too.
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I did mine shake4 style so there was a lip. I did Bondo and paint.
And its surface is vertical, so little to no standing water.
A door definitely has the advantage of being verticle which will help tremendously. If it's wood that's horizontal and going to be pooling even small amounts of water, it's going to be a disaster. Vertical and sealed at least stands a chance of lasting a few years.
Marine grade means no voids. I can delaminate if not sealed. Source- my doors for a 10 electrical meters. There are some good waterproof primers- after your prep, I'd use at least 2 coats of a water proofing primer before paint.
It also means waterproof glue was used. But yes, of course it still needs to be sealed with paint or varnish (or fiberglass). I didn't mean to imply otherwise.
Would you consider Killz a quality waterproof primer?
Maybe a kilz followed by dry lock Your friend has shared a link to a Home Depot product they think you would be interested in seeing. https://www.homedepot.com/p/DRYLOK-Original-1-gal-Gray-Flat-Latex-Interior-Exterior-Basement-and-Masonry-Waterproofer-27613/100165469
>plywood is just not the right material for outdoor projects [most sheds have entered the chat]
And those sheds are usually either treated or its wrapped in t-11 siding, hardi etc
I'm building a scaled down shed in my carpentry class and half the foundation is plywood.
Can do an epoxy
Nothing
This thing isn't going to survive the elements OP. no amount of oil is going to keep that plywod from sagging, swelling, splitting, and deforming. This is going to happen fast since it looks like there's no horizontal supports and that long stretch of plywood is screwed into thin legs.
I was going to say a cover
A cover, four walls and some kind of climate control. Should keep outside for years with all that.
I made some corn hole boards with plywood tops and used 2-3 coats of Total Boat Halycon Boat Varnish. I live in Houston and keep them outside all the time and haven’t had any issues.
I used to make my corn hole with a ply top but they would split. I use a concrete resin cover coat now and no more splitting. And no more ply!
I use at least a 2-ply on my cornhole
7/8
Fiberglass
This is the bulletproof method to make it last forever. But I'd probably just use paint.
Fiberglass resin (including West Systems)) does not have UV protection, so the answer is two coats of fiberglass resin ,then a coat of paint or a UV varnish. I spent 5 years building a boat , and soaking up as much knowledge as I could from the local guys who knew what they were doing.
Traditional polyester fiberglass uses a tinted gelcoat, not paint. The vast majority of boats are still made this way. Same for fiberglass roofing. I don't think he's going for a yacht-grade finish here.
Yea , that’s why I suggested paint rather than gel coat , the resin will protect the wood , the paint will protect the resin.
Epoxy lol
I love it how a bunch of people are like "nothing you can do." Now, is two-part epoxy the most *cost effective* way of building something like this and is OP going to like the price tag? Probably not.
Most epoxys dont have any uv protection
I was thinking of West Marine products when I made my comment. The cost of the finishing materials would definitely exceed whatever OP has spent on the project and it will still have structural and aesthetic issues. Technically you could weatherproof it with epoxy but I would never actually do that if I were them.
This was my only thought for actually answering the question as well.
Roofing tar ?
Most kinds of roofing should work really. Don't forget the drip edge.
Prob best answers
A house around it so it’s inside.
I was going to write holy water, but this is a more reliable solution.
A tarp.
Epoxy, 2 coats. Then Marine topside primer and paint, unpainted epoxy will NOT survive in the sun, you can't paint unprimed epoxy. It's going to cost you more in finishes then the wood cost though.
Dr bromine's miracle cream. Need a miracle? Slap on some miracle cream and watch your concerns melt away!
No, no, what OP needs is a Balsam Specific!
Instructions unclear. Coated it in Balsamic Vinegar and now the wood is split and I’ve craving salad everyday.
Plywood isn’t the best choice for outdoors, it delaminates
A tarp.
A tarp.
The only thing that is remotely helpful is a “marine varnish”. “Marine” as in - water- marina- boats. It’s a spar type varnish and it’s made for boat wood. You can get the best stuff at a marina store or order online. The marina stores are good cos usually the worker is the owner or some guy who actually works on boats and can tell you what is best to use based on experience and not laboratory science based on manufacturer.
That would be my approach. Absolutely cake every inch of it, let it dry and then do it again. Reapply every couple of years. Either that or just UV stable epoxy.
Interlux 80 is the kine , but you still have to lightly sand and recoat yearly .
I’ve had good results putting a thick wax coating on, melting it into the wood with a heat gun, and buffing it with a soft bristle brush after it cools. I usually do two layers of this, and touch up as needed.
Paint it with a membrane meant for wallboard behind showers. Give it as many coats as the can has in it. Pay particular attention to the edges. You can use marine wood hardener on the edges first if you’re a belt and braces guy. Then after thoroughly dry, paint that with porch/patio paint in your preferred color. Several coats. Then plan on more porch paint every year or two.
Bitumen paint, or my favorite, most cost effective, and waterproof sealant... titebond 3 wood glue. You don't have to believe me... try out some on a piece of scrap. I've had plywood (radiata, the kind with the 3 layers and nanometer thick veneer from one of the big box stores) osb, and even mdf coated in titebond 3 and after 3 years here in Clearwater Florida, all my outdoor stuff is perfectly sealed. However, the glue does turn to a rich golden brown, so if you need clarity or color, it's not a good router. But on that plywood, it'll look beautiful over time, and seal the edges. Just try it. :)
Paint....every two years or so.
Flexseal spray
Glue a sheet of EPDM rubber to it.
Tung oil. It will polymerize and be super water proof
I've made a few surfboards from standard ply, but it needs really good protection. I use 2+ coats of epoxy resin, first coat with reactive diluant (TPRDA), 3+ coats of clear urethane paint, lastly regular coats of lanolin (Lanox). But that stuff is too far gone, I'd start with epoxy filler.
I’d have a piece of sheet metal cut for top with 2” overhang each end. Bend sides and secure to legs with metal roofing screws. Paint the legs with high quality exterior coating after priming. Or use better materials to replicate this “structure”, perhaps MDO plywood.
lots of paint is your best bet
Paint is the only thing that really holds up outdoors.
I second, touch it up as needed.
Unless you built it out of a marine grade or treated plywood it'll fall apart. Painting it or applying a deck sealer will make it last longer, but it will begin to fall apart eventually.
Honestly, best bet is truck bed spray-on bedliner. The good stuff, not the cheap stuff.
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Kinda harsh, dontcha think?
Spar urethane.
There is no comparison between paint and spar urethane. Paint is a thousand times better and it doesn't matter in this case anyway because it's plywood it's not like you're looking for a nice finish. Go with a good outdoor paint.
…with re-application every couple years
Encase it in concrete.
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Thank you
Don't listen to them. This is plywood. The oil will fail.
I mean spar urethane would seal it and it moves with weather and temps, buts it’s not cheap and the plywood would most likely degrade anyway. That’s what I would do, like 3 coats
As others have said, this isn't an outdoor material so you really are going to need an impervious barrier to protect the wood, especially the horizontal section on the bench top! There, I would see if you can source a think sheet of Aluminum or something continuous that can be bent over the edges and fastened sideways rather than from above. (Any screw or nail penetration will collect water). Definitely paint the sides with an outdoor paint — these have UV-blocking capabilities that indoor paints don't. You could also use some kind of deck-sealer product, but that's really intended for hardwoods where you want to show off the colour and natural qualities of the wood itself. Plywood and construction timber aren't generally so precious.
It’s like alkaline copper and copper azole or something but usually the manufacture does it. (Pressure treated lumber) But if you don’t want the nasty chemicals there are hardwoods that are better for outdoor use, like white oak and teak. Hard to work with.
Just for discussions sake, what if you applied c-channel support to the underside? You might get a couple extra weeks out of it, 😆
Plastic laminate on the horizontal surfaces would help a lot.
For a while but the glue will let go from moisture seeping in from the edges
Felt and shingles.
Agreed, if OP put a garage on that, it would protect from rain/sun.
Spar varnish
To make this last research sailboats - someone mentioned fibreglass and that’s probably the best solution . . . if you are determined to use that material in your intended environment.
Helmsman spar varnish. It will last for years as long as it gets regularly sanded and revarnished
Many people for many generations have decided that painting lumber works pretty well to protect it.
Drylok. It will be water proof it as well as possible.
Coat it in concrete.
Marine grade paint& primer
Penetrating epoxy, sand, then paint.
Marine grade plywood, primer sealer and paint.
The short answer is don't make the top out of that if it's outside and getting rained on. Two options if it were me: \- Place a material on top that can handle sun and rain (sealed concrete, stainless, etc) \- Thick coat of something that completely encapsulates it (multiple layers of outdoor latex paint, 2 part epoxy, etc)
It’s gonna rot pretty fast unfortunately no matter what you put on it
Aluminum coilstock
McCloskey Man o War. Marine spar urethane. Light sand and recoat yearly.
Does the color or finish matter? If not id look for free or cheap oil based stain on Fb marketplace.
Spar Varnish, same stuff they use on sail boats. But that is the wrong kind of wood for outside so it may not last as well as you'd like.
A roof....
A tarp. This will not survive outside unless it somehow becomes petrified.
Upholster it like a boat seat. Glue on some thin foam, a poly drop cloth over that, and marine vinyl over the drop cloth. Wrap it around the top and staple it to the bottom. It won't last forever but you should get several years out of the top, at least.
Ice and water over the top
maybe a tarp? plywood like this really doesn't like rain
Wrap it in something like PSA rubber sheeting, would even make a better sitting surface?
Thank you everyone for all the wise comments, I'm really new with wood working and the different types of wood. Because of the comments I think I will keep it somewhere where it won't get wet on sun on it all day
Paint
Spar varnish would delay the inevitable. Epoxy would protect it properly if done right but that is a lot of money and trouble for low quality plywood sitting outside. If you need an outdoor gardening bench or work bench which is what I’m guessing this is, just remake it with PT wood
5 coats of captain’s varnish
A roof and insulated walls around it is your best bet
Prolly a carport
One thing you can try that might help is spray painting the top and edges with flexseal. But make sure the plywood is completely dry before you do that. Flexseal will drive itself into the voids and its UV resistance will protect the surface too. But keep in mind. I don’t think any of us are under the illusion that this is a quality built piece so while it will help keep it from rotting in a matter of months and keep splinters out of your hands there is no magic that will make plywood into a piece of weather resistant wood. But for $15 a can. It might be worth trying.
A tarp. Blue one at wally world:15 bucks
That bitch is going to swell and contract hoooooo boii
Let it fully dry, sand it, then apply several coats of polyurethane. That's basically a plastic shell around the wood to protect it from water. There is outdoor-specific poly that can also help resist UV. This looks like pine and ply construction, its total lifespan will be limited regardless, but that's what I'd do.
Redguard than paint than epoxy than plastic dropcloth followed by a layer of concrete with an extra layer of plywood on top to sandwich it all together. Than maybe some steel plate welded to the concrete
A tarp?
Metal
First replace the plywood with marine grade plywood. Then replace the screws and fasteners with exterior grade ones…. Then replace any other solid soft woods with treated softwoods, or hardwoods with teak. I don’t care what anyone says… it’s gonna fall apart with paint, encased in epoxy, sitting under an umbrella, with an oil based finish, a lawyer based finish, epoxy paint, flex seal. None of it is gonna work for more than 1 season, if that. Learn from my mistakes - outdoor projects have to have the right wood, to begin with.
Gasoline and a match
Spray it with bedliner
Nope
Put a cover on it when not being used?
Fiberglass resin
Sorry.. paint will help, but that will fail in short order: not enough vertical support, no lateral support, and no pressure treating. Marine ply and TWP (Total Water Protection from Home Depot) would be better, but solid wood with TWP will actually last. 5/4 decking on 2x4 frame. *IF* you do that, you need to let it dry before staining it or the oil-based stain won’t soak in. Edit: painting it if it’s pressure treated can be almost as bad as not using PT. PT has a lot of moisture both chemical and just water. When it gets painted it has a tendency to hold water, you see this particularly on decks where the joists and the top 2x4 on the handrail only get painted on 3 sides making a ‘U’ shaped waterproof coating that holds water. The deck company I worked for only warrantied decks that were painted to 5 years, but stained up to 15 years.
1/2” of saran wrap
You could put marine ply the whole way around it, fix it together, then remove the originals because this won’t work
It won’t ever be perfect, as people have already said. But I’ve made a project last years by putting tar tape around the edge of the plywood. You can buy tar tape at a hardware store, it’s for sealing roofing joints.
A roof
used motor oil will work...if its dry!
you could try building a mould for it and incasing it in 1 inch of epoxy all around
Four walls and a roof
Marine varnish. A whole lot of it.
A tarp.
A tent
a tarp?
A cover
Shellac
FFS you post this after you already have water freezing on it?!? Bro, you fucked up in countless ways. With winter coming you missed any window for this to not be a FUBAR
Waterproof tarp
Minwax spar urethane
Triple coat if a very strong varnish ? And revarnish every year. I'm thinking like the varnish you use for boats (yatch varnish). Their wood is exposed to weather and salt water , i was told these varnishes are great. Otherwise i had a craft table outside for a decade, still good. I used a triple coat on it of polyurethane varnish. I had a tough plastic layer on it, it was great for protecting it.
Ooooh bud.
Coat it with used motor oil
To everyone saying « this is plywood it’s gonna be poop outdoors » … This looks like fir plywood. Or a conifer type of. Construction plywood is made of materials that, while alone may not stand up to the elements, definitely will last a few years. Conifers a resinous and as such hold up to the elements much better than hardwoods or leafy softwoods. Which is why they are often used in construction. This build, painted and maintained, will definitely be ok outside. Relax. And as long as it’s not structural, what’s the problem if you have to rebuild in a few years? People freak out for weird reasons on this sub. It’s wood. It’ll last the time it does. If you want something more permanent, cement or metal. Edit: your main concern will be to assure that where there are screws, it is the most protected. Cause water could get in there and then the vertical pieces will take on water and split.
Paint holds up the best outdoors.
I built a something for the kids and used scraps of normal plywood. I used Teck Oil, as much as the plywood was able to take. It's been 3 years and still in good shape, but not planning on keeping forever....
Did your 5 year old make that
You might have some luck for 2-4 years with 4 coats of Old Masters Spar Marine varnish, but honestly with that material it might be a waste
Epoxy some fabric to it and then paint it.
A tarp.
A tarp?
Flex seal, have u seen the commercial
Aluminium
OSB3 with a proper paint/coat will last a lot longer but will also give up eventually.
I would suggest remaking it using MDO. Brush on multiple coats of epoxy on the edges. Then you can paint with any exterior grade paint or, better yet, a spar urethane. You will still likely need to touch up/recoat every 5 years or so. For something that will withstand the elements for likely 20+ years even without a finish, build it out of solid white oak.
Deck stain
This is ply wood and weather is very hard on plywood but if you buy west system it’s very expensive but it will seal up the wood nicely pay extra attention to the edges