What is the best way to install slab on grade insulation?
I am planning on building a small house 35 x30 that will sit on a slab on grade. I'm planning on installing some kind of wood floor so my question is. Would it make any sense to install rigid insulation between 2x3 every 12 inches and cut down on the amount of insulation under the slab? Also, how do feel about using this 1 1/2 inch space to run pex and electrical wires if needed. I only discovered this site yesterday looking for information on slab on grade, a lot of really good information here. Thanks
No, I would stick with below the concrete. You are simply adding work and cost for no particular value. The labour it takes to increase the sub-slab EPS foam insulation is nothing compared to the labor required to switch to an entirely different method of insulating. I would first point you to this page -
Slab on grade technical guide
We have other pages on slab construction as well that are worth looking at, you can find them if you enter slab on grade in the search bar at the top.
As for your Pex tubing and electrical wires, I would put them in conduits right into the EPS foam base. As for flooring, if you do it properly – meaning sufficient insulation and protection from moisture – you can lay wood directly on a slab floor. Make sure it is engineered wood and not solid wood, as solid wood will be at a much higher risk of cupping or warping due to any moisture left in the slab. Just be sure to check with the wood manufacturer that it is suitable.
Remember that there is a lot of water in concrete, so wait as long as you can to let it dry, and if possible try to cure first. If you are installing radiant heating in the floor it would good to run in for a week or two to dry the floor before you install wood.
Mike
Under the slab, it is, makes sense for the reasons you listed. The conduits suggestion is a good one also, i can use that. Thanks for taking the time to reply to my question, appreciate it
Paul
Happy to help Paul, good luck.