Rigid Insulation Under Basement Slab

Evenly spread the base gravel under the basement slab keeping it 1 inch lower than the conventional method.

Rigid insulation under basement slab.

A careful evaluation of these materials performance attributes against the project s needs can dramatically shrink labor and material costs. View the owens corning basement and crawlspace insulation 48 78 48 78. 4 10 2012 3 climate zones e301 1 6 5 8 4 slab r value table 402 1 1 insulation and fenestration requirements by component e402 1 1 climatezone slab r valued 4 10 2 ft 5 10 2 ft 6 10 4 ft 9. Tape the joints between the boards with builder s tape.

As the slab will only be able to dry upward the slab should be allowed to dry before finishes are applied. Additional insulation is applied along the edges of the slab because that is a primary surface for heat loss. Dupont styrofoam brand extruded polystyrene foam insulation is an ideal solution for under slab installations offering the following advantages. Place a 1 inch layer of 4 x8 extruded polystyrene foam board over the gravel covering the entire floor area.

Get free shipping on qualified under slab foam board insulation or buy online pick up in store today in the building materials department. If the foundation is on frost susceptible soils install a layer of impermeable insulation horizontally in the soil at a slope ratio of 1 5 for at least 1 m 3 ft. For under slab applications the rigid foam insulation typically should be installed over a gravel base with a poly vapor diffusion retarder between the gravel and insulation. You want to create a tight insulation layer.

Insulation is applied to houses with slab on grade foundations exactly as you would insulate the outside of a full basement see section 6 1 insulating the basement from the outside. Insulation located below grade as required in climate zones 4 through 8 should extend the length specified in the table by any combination of vertical insulation insulation extending under the slab or insulation extending out perpendicular to the building insulation extending perpendicular away from the building should be protected by pavement or by not less than 10 inches of soil. For installation on concrete foundations and under floor slabs the rigid foam insulation you choose can make a difference of tens of thousands of dollars on a project.