Home>Discussions>YARD & GARDEN>Decks, Patios, & Porches>best material for shed base(plywood or osb)
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Bill Potter
best material for shed base(plywood or osb)

A newbie here with a question.
I'm building a shed base that will be approx 8'x8' and will be made with pressure treated 2x6's 16" on center.It will be supported on cement piers on the corners and middle.

Can anyone tell me which would be the best choice for the decking? Should I use Pressure treated plwood,or Tounge and groove OSB board.
I'm placing a vinyl shed of 7'x7 on top of it.It's just a shed at my summer camp trailer,and the ground is very dry.I don't want to use a deck material that will need replacing a few years down the road.
I'll run aluminum drip edge around the perimiter edges to keep any water away from the wood edge.

Any input would be appreciated, Thanks B.P.

A. Spruce
Re: best material for shed base(plywood or osb)

Plywood, and since you're using it for a base for the shed, pressure treated wouldn't hurt, either that or paint it really good. You don't need T&G, just support the seam with a joist. Also, unless you're going to flash from the shed to the outer edge of the platform, edge flashing isn't going to do anything but hold moisture on those edges.

OSB is garbage, it isn't good for anything, let alone to leave it exposed to the weather.

Re: best material for shed base(plywood or osb)

Spruce's right, don't even think of using OSB, no matter how inexpensive it is, for exterior use.

Go with 5/8" plywood.

If you have a gable roof, installing gutters and spouts to take rain water away is fairly simple. Do that.

Timothy Miller
Re: best material for shed base(plywood or osb)

Howdy, locally osb an plywood are about the same $. so i would use plywood since it can stand water better then osb. how much weight are you going to load the floor with if bunches consider floor joist 12" on center then 1/2 osb or plywood would work out. If you want the shed to last a long long time consider marine grade plywood its $$$ but darn near indestructible.

Re: best material for shed base(plywood or osb)

3/4" PT plywood, no question. I would not use a drip edge unless it was flashed all the way to the shed walls. Anything but PT plywood that close tot he ground will attract insects like ants and termites.

Consider making the base 7x8 instead of 8x8. The back and the sides of the shed would line up with the floor and the front of the floor would stick out 1 foot as sort of a step or porch. This would be easy as you would cut each sheet of plywood to 7'. Run the joists front to back, slightly less than 16" OC (14" OC) with blocking under the seam between the two sheets of plywood.

Now you can run a Z flash under the shed walls and over the sides of the plywood on the sides and back. Caulk along the front seam to keep water out of the shed. Instead of making the floor perfectly level, slant it so that the front is about 3/4" lower than the back. This will also help keep water from entering and getting trapped in the shed, and a pitch that shallow will be almost not noticeable.

Re: best material for shed base(plywood or osb)

I would definitely use plywood and paint or seal it well. If OSB even has an area that water can drip on it it will deteriorate rather quickly. I didnt see in your description but I would also plan on putting a block foundation (or those concrete formed post stands) under your frame to help it off the ground a couple inches. The further off the ground it can be, the more air can circulate and that means less moisture and insects

Edit** I saw in your description about the concrete piers good idea there you're on the right path

Bill Potter
Re: best material for shed base(plywood or osb)

Thanks to all of you for the good info.Looks like I'll be going with the pt plywood.
I thought about using Marine fir plywood,as I deal with it a lot when I do boat restorations,but in this case I actually think the pt is a better choice.

Re: best material for shed base(plywood or osb)

pt ply 3/4
why have the deck that much larger than the shed?
sounds like trouble.

Bill Potter
Re: best material for shed base(plywood or osb)

The new deck won't extend beyond the shed on the sides or back.
The front however,will tie into an exsisting deck already in place,so the sheds entry will be on the same plane.
The reason is,because I'm adding on to an existing deck that is 32' long and runs along the front of my camp trailer.
I'm placing the new deck for the shed at the end,and around the corner of the existing deck.The shed will be protected by the rear of the trailer.
the new portion for the shed will be tied in to the existing deck.
I want it all on one level plane,so that we can walk down the to the end of the deck and have the sheds entry on our right,and behind the end of the trailer.This will leave the view to the road and lake wide open,and access to the shed very easy.
This is a trailer that is stationary,and primarily a summer fishing camp.
The deck that is on it now is a permanent structure,on concrete footings with an asphalt shingle roof.
At some point I'm going to extend the roof of it around the corner,and over the shed.

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