insulating a skid foundation

eric · May 14, 2008, 04:08:26 PM

Howdy,

I did a search for this subject and didn't see anything that quite answered my question so here goes. I'm wondering about building a 10'x18' structure on a skid foundation that would serve as a temporary dwelling until a larger dwelling could be built. I wouldn't plumb it but I would want to insulate it, including the floor, and use a small woodstove for heat.

I'm wondering if anything is wrong with a floor system scenario including these components from the ground up - gravel, skids, vapor barrier, plywood, joists with insulation, subfloor. It could be built in sort of panelized sections which would only include the vapor barrier, plywood and joists; then those panels could be laid on the skids (vapor barrier face down) and fastened to each other and the skids; then insulation could be installed and the subfloor could be put down.

I just realized it might require a long sort of rim joist along the sides to strap the sections together. I'm not sure if rim joist is the right word but it would be similar to a top plate in vertical framing, something to strap it all together and make it more rigid.

What do you think?

mvk · May 14, 2008, 05:30:25 PM

Eric
It would really help if you gave the location so people could get some idea of the climate/building conditions. How cold, how wet? Maybe you have in another post and I missed it?

Vapour barriers should be on the warm side of the living space, but you have to consider moisture coming up from the ground, I would guess that is what you were thinking. How close to the ground will you be. How long will you be in this building, what will you do with it when you move into the house, shop, office, guest house, could you just use it as addition to future house? If I was doing this around NH and wanted to keep it as a heated space after I moved into the house and was close to the ground I would use PT skids, PT frame, PT ply, 2" of blue or pink foam then subfloor. If I just wanted to live in it till I got into the house I might try to scrounge a couple layers of carpet underlayment and some carpet. A small building with a wood stove will stay pretty warm.

Mike

May 14, 2008, 06:27:17 PM

If you edit your profile there are a couple places you can put location info. It helps a lot.

You may want to put a barrier on the ground depending on conditions - take the main part of the drainage away before it gets under your building - ie: slope away with it high or on a mound.

eric · May 14, 2008, 06:44:18 PM

Thanks very much Mike.

I'm in the inland northwest. 25 or so inches annual precipitation. It gets pretty cold. Several feet of snow sometimes. The land we're currently working on getting has sandy well drained soil. I hope we wouldn't be in this building for more than a year. I was planning on 6x6 PT skids, so it would only be 6 inches (5 1/2"?) off the gravel. Oh and I will put gutters on it, and direct that water away from the building.

I imagine the building still being used and heated after the main house is built. It could serve as guest quarters / creative space. It wouldn't work to add on to it in our situation.

I could use kraft-faced batts in between the joists to add a vapor barrier to the interior. Or just use cellulose with a vapor barrier immediately beneath the subfloor in addition to the one on the exterior bottom.

I would definitely use PT skids but I'm not a big fan of PT lumber. But the scenario you described is interesting. Wouldn't you have to put some sort of true 2" wood in with the foam, or can the foam actually carry a load (foot traffic, furniture, non load bearing wall) without compressing? At the edges, you can't transfer the load from the studwalls through the foam to the floor frame, could you?

Thanks again Mike.

Glenn, I'll edit my profile, thanks. Mound sound good. Mound sound good. (I have a tendency to degenerate to caveman speak)

glenn kangiser · May 14, 2008, 07:45:49 PM

I should understand you fine then.

Just use the foam for infill. I have seen some of it used under concrete but the concrete still came to the ground under the structural areas. There are different types.

May 14, 2008, 09:02:28 PM

Just lost my post and I type so slow

Yeah I meant to use the foam as infill. I would also use solid wood at the door sills.

I don't like treated wood either but around here anything that close to the ground would rot out pretty quick.

That blue or pink foam doesn't seem to be affected by moisture so much. Fiberglass or cellulose wouldn't work so good down on the ground IMO

Have you thought about a camper/travel trailer as a temp.

How about this as part of the house and put a foundation under. Do you have permits to worry about. What kind of foundation will you have? Used to be able to cap your cellar hole and build pay as you go around here but they won't give you a occupancy permit anymore

poor people go away

Mike

glenn kangiser · May 14, 2008, 09:12:51 PM

You need a permit to occupy your own land? hmm

...and I was under the illusion that this was a FREE country....guess I better open my eyes.

TheWire · May 20, 2008, 02:48:46 PM

Owens Corning pink foam comes in a couple strengths. The FOAMULAR 250 has a compressive strength of 25psi or 3600 pounds per square foot.

My cabin has 1/2 PT plywood for the 1st floor deck to deal with rain during building and crawl space moisture once its done. I plan on putting 1" T&G foam over the PT Plywood, taping the seams, then putting 3/4 T&G OSB on top of that. Not a huge amount of insulation, but enough to keep the low outside temps away from bare feet.

Jerry