Shed Flooring - DryPly

Bmonkey · 10-01-2012, 12:22 AM

All I am building a shed in my back yard. 12x16. It is elevated off the ground vertically 4-12 inchs on solid concrete blocks. (Downward slope from front to back.) I just got done building the frame for the floor out of PT Lumber. I ended up getting 6 sheets of 3/4" T&G DryPly for the floor. It has a waterproof coating on the top for water resistance during install but the bottom is Raw Wood. I think I screwed up here. However I would like to use it as it nice material and should make a great floor.

Is there anything I can do to utilize this material in my shed. I have heard of people using 6mil plastic as a vapor barrier between the joists and floor. Not sure if this is a good idea. Also hear of people putting their own wood preservative on the raw side. Not sure how long that would last

I was toying with the idea of picking up some 1/2" PT plywood and nailing it down, then placing the 3/4" DryPly on top. Any issues with this? Is some sort of membrane needed between the two? Felt Paper? There should be good air flow under the shed and I have heavy duty weed guard down with 3-4" of rock on top

allthumbsdiy · 10-01-2012, 07:34 AM

I think if you have plenty of air space underneath with stones to drain water away, you would be fine with what you have.

If you do decide to put 1/2" PT plywood first, just make sure your 3/4 joints are different

ps. when I built my shed, I put my floor joists on 6x6 skids so none of my framing members were pressure treated

joecaption · 10-01-2012, 08:28 AM

I would have built the floor out of Advantec Then a layer of 1/2 subfloor rated plywood instead of DryPly.
I would never use pressure treated between the layers of flooring or a vaper barrier under the subflooring like that.

If that shed was one more block high moisture damage would be a nonissue.
Building in an over hang for the roof, adding stone around the outside of the shed to reduce splash back, propper drainage on the high side of the slope. adding a vaper barrier on the ground with stone on top of it used under the shed will go a long way to prevent damage later.

hand drive · 10-01-2012, 09:40 AM

Why not use 3/4" treated, one layer and be done.

joecaption · 10-01-2012, 09:46 AM

3/4 pressure treated would be full of flaws and voids in the core, it's not going to be T & G, should not be used inside an occupied space, is going to shrink when it drys out.

Just look at brand new sheets of it still in the store. Your going to see just how bad it looks.

hand drive · 10-01-2012, 10:12 AM

Quote:

Originally Posted by joecaption

3/4 pressure treated would be full of flaws and voids in the core, it's not going to be T & G, should not be used inside an occupied space, is going to shrink when it drys out.

Just look at brand new sheets of it still in the store. Your going to see just how bad it looks.

It is not the prettiest stuff and it is back breaking heavy but it is a shed and because the shed floor is practically at ground level and the fact that it will not rot is the most important thing imo, Put the pretty side up and some construction glue will help hold it all down...

GBrackins · 10-01-2012, 12:07 PM

Quote:

Originally Posted by joecaption

If that shed was one more block high moisture damage would be a nonissue.
Building in an over hang for the roof, adding stone around the outside of the shed to reduce splash back, propper drainage on the high side of the slope. adding a vaper barrier on the ground with stone on top of it used under the shed will go a long way to prevent damage later.

joe is absolutely correct about it being higher. if you were required to pull a permit to construct your shed (12'x16' would require a permit in my state) you should be aware of the following from the 2009 International Residential Code, basis for most local and state building codes (your code may vary):

R317.1 Location required. Protection of wood and wood based products from decay shall be provided in the following locations by the use of naturally durable wood or wood that is preservative-treated in accordance with AWPA U1 for the species, product, preservative and end use. Preservatives shall be listed in Section 4 of AWPA U1.

1. Wood joists or the bottom of a wood structural floor when closer than 18 inches (457 mm) or wood girders when closer than 12 inches (305 mm) to the exposed ground in crawl spaces or unexcavated area located within the periphery of the building foundation.Not saying the inspector will catch it, or even enforce the requirement should you require a building inspection. just to let you know what the IRC says.

I typically use building wrap (typar) installed under all close to the ground (less than 18") structures attached to the bottom of the joists. this prevents exposure of wood to moisture, and allows the floor to breath in the same manner it allows a wall to. We then run the building wrap up the walls.

just my humble thoughts .....

Good luck!