Insulating below Concrete Slab
NightRaider
| Posted in Energy, Heating & Insulation on
I am getting ready to pour a new concrete slab for the garage. I am someone that likes to tinker in the garage all year, despite living in the Bay Area, the garage gets cold in the winter, so I thought about insulating before I pour.
What insulation should I use? Also, should I put down a plastic barrier between the crushed rock and the insulation? Can anyone make any other recommendations?
Replies
Unless you put some radiant heat into the slab or heat the garage all winter using other means, I doubt it will make a huge amount of difference. My first choice would be radiant to heat the place, it's nice when the floor under you isn't ice cold. In that case, I'd put in an inch of XPS over the 6 mil barrier, follow that by mesh, radiant, and another layer of mesh.
I always have a problem with load factors on a foundation with insulation under it. Foam board is just not going to hold weight and then the slab will crack.
Brown, the run of the mill blueboard is at least 15psi. T&G is 25psi. Dow also makes high load stuff that goes up to 100psi. Now my math could very well be off, but I think 100psi equates to 14,400 lbs/sqft.
Personally, I'd be more concerned about the compaction of the subsurface and concrete finishing causing a crack before I'd be worried about the insulation settling.jt8
The reason so many people never get anywhere in life is because when opportunity knocks, they are out in the backyard looking for four-leaf clovers.-- Walter Percy Chrysler
Like you, I doubt that the insulation will be a big issue. If the floor has to hold multiple fire engines, paving machines, and other heavy stuff, simply go up in the thickness and start using #4-60 rebar instead of wire mesh. You could even run some extra footers inside the space to support likely tire locations. I doubt it's necessary though.A civil engineer could come up with the specifics in no time at all, as they have to deal with commercial-grade applications all the time.