Leaving plywood flooring exposed to the elements

[Ignavus]

Hi all,
I'm building a sleep-out for holidaying on a section close to the beach, in New Zealand. It measures about 6mx4.2m (20' x 14'). Unfortunately between finances and time it is a pretty slow build. I'm just about to put the 3/4" plywood flooring down, and am not sure how long it will be between now and when it gets fully closed in. Probably at least 1 year. Does anyone have any comments on how I can make sure that the plywood flooring doesn't warp horribly in the weather? It is treated plywood, so I'm not too concerned about rot.

I had thought I'd just cover it in polythene sheeting, and staple that down. However I'm not sure if this will be sufficient. Should I give it a coat of polyurethane now, and then just sand & recoat it once the building is weather tight?

If anyone is interested, the (minimal) plans are available here:
http://www.ignavus.net/okains/files/okains_plans.pdf

Thanks,
Andre

[flyingvan]

Andre---I put poly sheeting down and very much regretted it---I had to put down a whole new subfloor.  It trapped the moisture in the wood and ruined it.  What I should have done is built a low tent frame and stretched a tarp over the whole thing with maybe 10" of airspace---this would have allowed rain and snow to run off, and still allowed wood to dry

[Redoverfarm]

Hi all,
I'm building a sleep-out for holidaying on a section close to the beach, in New Zealand. It measures about 6mx4.2m (20' x 14'). Unfortunately between finances and time it is a pretty slow build. I'm just about to put the 3/4" plywood flooring down, and am not sure how long it will be between now and when it gets fully closed in. Probably at least 1 year. Does anyone have any comments on how I can make sure that the plywood flooring doesn't warp horribly in the weather? It is treated plywood, so I'm not too concerned about rot.

I had thought I'd just cover it in polythene sheeting, and staple that down. However I'm not sure if this will be sufficient. Should I give it a coat of polyurethane now, and then just sand & recoat it once the building is weather tight?

If anyone is interested, the (minimal) plans are available here:
http://www.ignavus.net/okains/files/okains_plans.pdf

Thanks,
Andre

Not sure whether it is available in your neck of the woods or not but Huber makes a good product just for that application. It is Advantex.  Might check to see if someone has a similar product.  It is made to be waterproof for extended period of time.

What type of roofing are going to use?  If it is metal and you can afford to purchase it now you can temporarily use it.  Elivate the center to 2 -2X's thick and intermediate distance to 1-2X to give you a slope.  Just use scrap lumber and some blocks to hold it down.

Problem with ply is that it delaminates.