Expert: Dave Johnson - 6/21/2008

Question
I am placing an 8'x24' platform in my backyard in Northern California.  The entire platform will be roofed-over, and the first 16' will be walled in on all sides, giving me an 8'x16' storage shed with an 8' covered area at the end.  Front walls are 8ft high and back walls are 7ft high.

The platform is on a relatively level area with 6" of slope over the entire 24'.

My question is about the foundation, which is always the hardest part.  I have read about using Sonotube or forms to place concrete piers 2ft deep and 2" above the surface.  Can I place the foundation directly on top of the concrete piers?  If so, how would I attach it?  I am constructing the floor platform using the walls from a dismantled building, so it is 2"x4" joists covered with 1/2" OSB.

I have heard that wood floors should be at least 12" high to combat moisture/rot concerns.  Unless there another way to handle this concern, I am thinking I must use short 4x4 posts attached to brackets imbedded in the top of the piers.  Then my only issue is does the floor platform sit on top of these posts, or is it lag-bolted to the side of the posts?  If it sits on top of the posts, how do I attach them to the floor framing?

When completed, I would like to cover the exposed space under the house to give it a nice appearance.  Depending on the foundation method, what framing materials and method should I use for the covering?  The rest of the shed will be covered with a water-proof cement-tile board and then painted.

Answer
Hi Chris,
First, the piers: If available and to code in your area, I  think 4"x6" pressure treated posts would work very well. Bury them as deep as you like and leave a foot above grade... this would give you something wood to attach the frame and "skirt" to.
The skirt could be perforated vinyl, or lattice which can be vinyl as well. Skirt frame should be p.t. as well, to prevent rot.

Anything more? mail me...
Best of luck,

Dave

I'm a little concerned about the joists... if they are only 2"x4"
they may sag with a lot of storage...

Attach the frame to the posts by setting the frame onto the post tops and use some "SIMPSON" ties (at your local bldg mat'l yard.)