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I am building a shed and I am trying to do it as cheaply as possible. I am going to use 1/2" OSB for the siding and I am wondering what the best paint/sealer is to weatherproof it. We live in central Ohio, so it will take quite a beating from rain and snow. Thanks!

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    Home Depot sells 4x8 sheets of 'siding' for sheds. Not sure how it compares to OSB price-wise, but is definitely going to hold up better (and will take a lot less paint to cover) – DA01 Jun 22 '15 at 14:59
  • If you are referring to t1-11 siding it is about $30/sheet compared to OSB at $9/sheet. Thanks for the suggestion though :) – BWDesign Jun 22 '15 at 15:20
  • How big of a shed are we talking about? You may end up paying more for paint to paint the OSB than you would have going with t1-11. Remember to calculate the total cost in your calculations. – DA01 Jun 22 '15 at 15:27
  • Thanks for the pointer - that is always something to keep in mind. The shed is 12'x24'. I don't think using the siding would offer any significant price difference when it comes to the paint. The t1-11 must be painted or stained as well. – BWDesign Jun 22 '15 at 15:33
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    t1-11 can be stained with one coat, but the OSB likely needs to be primed + Painted and likely will take more than one coat. However, if you go the tyvek route (adding actual siding in the future) The OSB makes more sense now (in lieu of painting). But if you're hoping to do it 'once' and be done, I think the t1-11 may end up being quite competitive price-wise in terms of the big-picture. – DA01 Jun 22 '15 at 15:38
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There's no such thing. OSB will swell, warp, and degrade unless it's kept safe from sunlight and perfectly dry. No paint will do this. If you want to use OSB to sheathe the walls of your shed, you need to build those walls like the walls of a house: with a weather-resistant barrier like Tyvek over the OSB, and then cover that with siding of some sort. Vinyl siding is cheap and DIY-friendly.

If you want to build a shed out of a single material without needing to do any of this, I recommend concrete blocks.

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  • I appreciate your feedback. The plan is to put vinyl on it eventually, but not yet. I have seen painted OSB last for several years out in the weather without any significant damage. – BWDesign Jun 22 '15 at 14:11
  • Depends on the climate and the degree of damage you're willing to put up with. Honestly, vinyl siding and Tyvek are so cheap that I don't really see a reason not to install them at the same time you're building the shed. If you can't afford them now, just earn some more money until you have the extra cash or so for the rest of the materials. – iLikeDirt Jun 22 '15 at 14:31
  • If you must know, this is why I can't afford vinyl: gofundme.com/helpbatesrebuild We are saving every penny we can to put towards a new house, and the shed is only to house our belongings (the few that we can save) while the current house is demolished. – BWDesign Jun 22 '15 at 14:35
  • Oh wow, that's terrible. My condolences. I suggest you cover the OSB with Tyvek, then, and cover it in siding later. Tyvek is cheap and will protect the OSB better than paint, and it'll be part of the future wall assembly anyway, so you won't waste money buying paint. – iLikeDirt Jun 22 '15 at 14:38
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    @BWDesign If Tyvek is tacky, use 30 lb roofing felt and battens for that classic tarpaper shack look... – Ecnerwal Jun 22 '15 at 19:35
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I know this is old but.....I have A frame chicken coops made from OSB that I stain / seal with whatever deck stain Lowes has in their discount rack. I don't let any part of the OSB actually touch the ground; treated wood runners for that. They are several years old and holding up just fine. They suck up the stain / sealer but after several coats, the water beads and runs right off. No swelling and no issues on edges.

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Your reasons for needing a shed are exactly why you shouldn't use OSB as an external covering for your shed without something over it besides paint to protect it from the weather. Paint is not a moisture barrier. OSB grows and spreads mold exponentially faster than regular wood. If you're already having mold problems using OSB at all would be pretty bad idea.

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I recently built a camping shelter (12x24 wood frame platform with "roof" and "walls" with a tent inside) on some land I own. I was on a serious budget but I wanted it to be big enough to be worth while so materials suffered. I framed it out pretty good but when I got to paneling I ended up Frankensteining it.. For my (first) two short walls I went with painted OSB. I figured it'd be good enough for my purposes. Like others have said.. It swelled and started softening up within a few months.. In order to avoid replacing those walls altogether I just wrapped it in house wrap and that has protected it without issue. Looks like crap.. but this was never built with "looks" in mind.

I went with t1-11 for my front wall. It is SOOO much easier to paint t1-11 and it looks MUCH better than OSB covered in house wrap. Before my last wall, I ran out of money my wife would let me spend on my pet project.

Not exactly up to code... but I ended up doing that back wall in rigid foam insulation. with wood prices being as insane as they are now. and if you don't care about looks either.. it may be an alternative. (assuming you haven't finished your shed in the 5 years since your post. lol) It actually does a great job of keeping out water and standing up to UV. I sealed the joints and voila. Obviously you'd need to add some rigidity somehow since foam doesn't exactly tie a building together. Does a much better job than the OSB and T1-11 in retaining temperature (especially reflecting heat). I (carefully) used roofing screws with the washer to fasten to the frame. I can't drive up very close to my build site. So the negligible weight of these "panels" made them an attractive choice for me as well.

The "roof" is wood framing with more of the foam panels supporting a large tarp. I have to replace the tarp every year or so, and like I said, no one is going to accuse it of having a finished look. Nor is it sealed to keep out insects and mice.. but it's pretty much what I envisioned when I set out. Just a place to stay somewhat warm during the winter.. and keep all the junk I have out there dry. I got away with 288 sq. feet for under 800 bucks.

I stupidly built it under enormous hardwoods by a creek. So I am working on another (more solidly built) cabin at another spot free of large trees. It's just a matter of time until one of those trees drops a big branch or falls completely down on top of it and destroys it so I'm not spending much time/money/effort improving it.

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  • While this is an interesting story, it doesn't really address weather-proofing the OSB other to indicate a failure to do so. I'm not really sure that it's all that helpful nor does it add much to the answers. New answers and insights to old questions are always welcome, so please feel free to edit your answer to help highlight and specifically address the "weather-proof OSB" question. – FreeMan Oct 9 '20 at 11:40
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Have you considered using something like Thompson's Water Seal? They're designed for porous materials and wick away water, but I'm not sure how they'll hold up

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Bit of an old thread, came across it googling. But for anyone else who does. You can seal osb boards with bitumen paint. The type that dries so its no longer wet, but still slightly soft, like firm rubber. I did this for a winter shield for my outdoor aviary & its been up 6 years so so far & still in the same condition when I first put it up.

Bitumen paint is no different to felting it for shed roofs. So long water or sunlight doesn't make direct contact, it'll be fine.

Just remember to cover your fixing screws with it after or water will find its way in via screw fixings.

If there's a will, there's always a way!

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