OSB walls?

[K0k0shka]

I'm in the process of building my first coop. After reading a lot about materials and comparing cost vs performance, I decided to use OSB for the walls, and no siding. I read that it was comparable to plywood in every way, but much cheaper. I read about people using it on coops and recommending it. I was planning on painting all sides of the OSB (and the edges) with BEHR Premium Waterproofing Stain and Sealer. It's advertised as performing better than paint, because it absorbs into the wood and protects it better, as opposed to sitting on top of it like paint and peeling/chipping eventually. I'll caulk the seams between the OSB boards, too.

Now, I was feeling all good and accomplished with my plan, and then I happened upon some threads on here and another forum saying that I shouldn't use OSB for exterior-facing walls at all... that it's gonna warp, mold and fall apart... and I'm having serious doubts. To be fair, the most critical thread was very old - from 8 years ago - so who knows, maybe they make OSB better these days? Also, people criticizing it are saying that it won't last long untreated, but they don't seem to take into account treated (painted/sealed) OSB. I found other comments from other folks who have used OSB, painted it well, and it's been doing fine.

I already bought all my boards and stain and everything...

Please tell me your honest and, ideally, experience-based opinion! Given my plan to seal it well, do you think OSB could work? The coop will be raised off the ground sitting on cinder blocks, there will be no wet tall grass or shrubs around it. The roof will have metal roofing panels on top of an OSB roof board (with a tar paper underlayment) and will have 6 inch roof overhangs, and every surface of OSB everywhere will be sealed.

 

[Gray Farms]

Wow, that's one determined rat! Rats can chew through regular wood too, though. Might be easier with particle boards like OSB, but I guess no wood is really safe. When I was growing up we had mice chew through tin barrels to get to the feed grains on the farm. Is there anything truly rodent-proof?

Also, you say it won't keep predators out, but the example is of a rat. A rat is not a predator, it's just a pest. I won't keep chicks in there, just adult hens or at most, pullets... Would a rat be truly a predator and eat my pullets? The true carnivorous predators that eat chickens don't have wood-gnawing teeth... Would they be able to chew their way in?

Rats will absolutely kill and eat chickens. Racoons can dig/claw through OSB if they are determined to get in.

 

[wyoDreamer]

I have an old piece of OSB that I use to cover the sheep tank I use for the dogs to cool off in during the summer months. I cover the tank when I get home after work, so my setter will dry off by the time I bring him in for the night.
After 3 years, it is starting to fall apart, which is pretty good for the abuse it has been taking. It was never sealed/painted in any way. It has been laid flat on the tank every night so when it rains at night, water sits on it until I leave for work in the morning. And when not in use as a tank cover, it is leaning up against the house - again, out in the weather 24/7 365 days a year.
I think it will last for you, as long as you remember to paint it again as the stain/paint is weathered away.
Looking forward to seeing how your coop turns out.

 

[K0k0shka]

I used t1-11 for the exterior, OSB for interior, and shingles on the roof.

That's great, but it's not what I'm asking...

 

[Gray Farms]

Glad to hear, thanks. Do you repaint because it's wearing off and it starts to show, or just in case?


Full grown chickens??

I repaint just to keep a good coat on. It looks nicer to me freshly painted, though I doubt the chickens care. Sometime I do it every three years or four "very much dislike painting". It gets some wear from sun, ice, wind, chickens pecking a strip off, and just the wear of time. That heavy oil based enamel is really good paint. My oldest shed is getting new OSB this year its about 15 years old and the OSB is pretty much shot.

Yes, rats can with out a doubt kill full grown chickens. They are just as dangerous as a mink or weasel. Maybe more so as there is usually more than one. Though they are easier to kill because they'll eat the rat/mouse poison.

 

[Folly's place]

Our rats that year killed three nice bantam pullets before the bait got them all. Don't ever think that rats are okay!!! And, weasels can enter through any opening big enough for a rat.
Sooner or later, every possible predator will show up.
Mary

 

[aart]

I'd opt for and exterior grade plywood over OSB.
If you do use OSB go for a quality paint(and prep) rather than a stain.
There so much glue in OSB stain won't soak in so well.

Tho my shed door has OSB glued to a standard solid wood door.
Been here since I bought that place 20 years ago,
and it's a bit 'shaggy' but still holding up with no paint or stain.

 

[wyoDreamer]

Most of the OSB that I see out there is only Exposure Rated 1 - which means limited exposure to inclement weather. There is OSB that has a higher exposure rating, but I don't know where to get it. The problem with OSB is that it absorbs water more quickly and dries out slowly - thus rots faster than plywood. They have improved OSB by soaking the wood fibers in wax resin to make them more water-resistant.
Tests have shown that it is structurally stronger than plywood - compare up to 50 layers of wood fibers (OSB) to 4-7 layers of wood laminate (plywood) - more wood fibers matted together is stronger.
OSB is wood fibers mixed with a wax resin and glue and compressed into a sheet.
Plywood is layers of wood laminate stacked on top of each other with glue and resin between the layers - compressed into a sheet.

Most important is what you use to seal it with. My parents used a Solid Color stain on their deck, it is only a year old and pealing already. I used a Transparent stain that will not have the solids in it to water proof my chicken tractor. I will have to see how well it holds up. It did soak in a lot of the wood sealant on the first coat and not so much on the second, so I believe it is well sealed.

As long as the OSB is sealed well, it can last as long as the plywood. But if there is a spot for water to get to the sheet, it can swell up, start to flake and cause problems. Keep it sealed and you should be OK.

 

[K0k0shka]

I'd opt for and exterior grade plywood over OSB.
If you do use OSB go for a quality paint(and prep) rather than a stain.
There so much glue in OSB stain won't soak in so well.

The price difference is significant though... This is already an expensive project. I'm just trying to keep it from blowing my budget even more I've been reading about OSB though, and it says it does accept stains and sealants... I guess we'll have to wait and see. If the stain doesn't seem to be doing a good job, I can paint over it with paint at some point. Or maybe even put siding on the coop. As long as it's spaced out in time, like maybe in a year or two, so the cost is spread out more.

Tho my shed door has OSB glued to a standard solid wood door.
Been here since I bought that place 20 years ago,
and it's a bit 'shaggy' but still holding up with no paint or stain.

Oh that's not bad at all! 20 years and nothing on it, and it's just looking shaggy (and not falling apart). I'll take that! My hope is that with treatment, I can prolong its life even more. That's what's frustrating about searching for information on this subject. All the hits are people complaining how horribly it holds up, how it falls apart, but they're talking about completely untreated OSB left out in the elements. Who leaves untreated wood out like that? Of course it's gonna rot and warp and whatever. Doesn't mean the material is poor necessarily... all wood rots outside if untreated... It's just not fair to the OSB

 

[aart]

Perhaps a little clarification by me is in order.

Or you could just link your coop thread
https://www.backyardchickens.com/threads/coop-is-off-ground-by-4-feet.1330749/