OSB panic

[Mark Burnette]

I'm adding on to the back of my shop to have room to store more stuff. Due to the recent heat and other delays I haven't made as much progress as planned. It's post & beam construction and the posts are in, the beams installed & level and the floor is in. The floor is 3/4" t&g OSB over joists, glued & secured with ring-shank nails. I don't have a roof up and tomorrow I leave on vacation for 11 days. I've thrown a tarp over the decking but I'm afraid water will get through or be trapped and ruin the OSB. I don't know what tolerance OSB has for standing water. I see it on unfinished roofs but my floor has zero pitch for drainage.

Will my decking survive any bad weather? Taking up a glued & nailed floor would be a nightmare. I'm in a panic--is there anything I can do in one morning to insure my floor is OK when I get home?

[Jamie Buxton]

OSB subfloor gets rained on pretty frequently. Think about it... When they're building a house, the subfloor goes down, then they build the rest of the house on top of it. Until they get the roof on, the OSB gets wet any time it rains. Okay, maybe it isn't the optimum thing in the world, but it happens a lot. In fact, what you often see in subfloor is drain holes. When water pools on the subfloor, the builder punches holes through the deeper puddles so the water drains through.

[Alan Schaffter]

Are you sure you used OSB and not Advantech? Advantech is waterproof (and a better choice for subfloor- more rigid and stronger!)

How about a squeegee, $20, and a neighbor teen in case it rains? Or some tarps? Whatever is cheaper.

[John Lifer]

It'll be fine. quit worrying about it. I've got 5-6 sheets that the PO of my house left behind a storage building. Going on 3 yrs now and he had it over a boat before if blew down for a few years. Only what is touching the ground is deteriorating.
Few days with water on it won't hurt it.

[Mark Burnette]

Then maybe putting a tarp on it is worse than nothing. After a storm yesterday the tarp kept 99% of the water off the OSB but some got under neath and couldn't dry out.

Maybe I'm just paranoid but the subfloor is so perfectly flat & smooth I want to make sure it stays that way so whatever goes on last will also be flat & smooth.

[Steve Southwood]

Go on vacation and forget about it. If you leave it exposed all winter and snow would set on it, then yes you would have a problem. Enjoy your trip.

[Jerome Stanek]

You could tent it with the tarp leave a space for air the circulate.

[Bob Cooper]

Like one of the previous posters mentioned. Your subfloor is probably Advantech or SturdiFloor or equivalent. They get wet all the time during construction.

[Van Huskey]

As others said the stuff gets water on it all the time in construction. When we built our last house we had a TON of water on the floor for several week! It was 1 1/8" Sturd-I-Floor though (ply), it delaminated in a couple of places but it ended up being a non-issue but I freaked about it the whole time.

[Mark Burnette]

This subfloor is standard t&g OSB. I wasn't aware there was anything better, so I didn't order anything better. There are a couple yards not far from here that carry Advantech & I might use that as my top layer.

I found I had a gallon of wood sealer so I rolled that over all the seams and put away the tarp. Fingers crossed.

Looking for answers on the web I found lots of comments about OSB sitting out in the rain coupled with lots of mentions of having to sand it before installing flooring. Even Advantech which claims to be the best for water repellancy only guarantees it flat for 300 days of exposure

[Mike Wilkins]

OSB is made with adhesives that contain a waxy substance that resists water. Manufacturers know that a house is sometimes exposed to the weather until it is dried in, so this normal.

[Alan Schaffter]

Advantech is denser, tougher, stronger, smoother, and more water resistant than OSB. I love it. Except for deck paint, just one layer of it has been my only shop floor for the past 8 years. Someday, when my ship comes in (or when you guys buy tons of I-BOXes ), I'm going to put down oak flooring!

[steve swantee]

Mark, can you share some pictures of your progress as you build? I am thinking of a post and beam addition to my shop and am interested in seeing how/what you're doing.

Steve

[Jim Andrew]

The first time I used OSB subfloor, the lumberyard sent out the cheap crap instead of the good stuff they were supposed to. I wasn't familiar with the stuff so went ahead and put it down. We got some rain, and the stuff swelled up around the edges, we wound up having to use a floor sander to level it off, and put a layer of underlayment over it. The rest of the stuff they sent out was a much better grade, and rain hardly bothered it. Course I found out later it didn't hold nails, when you try to put wood floor over it, so made sure I used plywood after that under wood floors. Plywood doesn't always stand up well to rain either.

[Tom Fischer]

I've used OSB scraps to make outdoor planter covers for my wife's stuff (whiskey barrel planters, etc). The OSB has been outside for two winters. Rain and snow roughens the texture, but still going.