Slab Insulation Details

Slab Insulation Details When Using Stem Walls:

Below are two methods for installing slab insulation when using stem walls. The depth of wall will determine which method is preferable. For example in Detail 1, the 2 x wall + drywall + molding are deep enough to cover the top edge of the foam; thus allowing the tack strip to fasten directly to the concrete.

Detail 2 is used when the total depth of the wall does not cover the foam insulation, thus creating a situation where the tack strip could “co-mingle” with the foam. By cutting the foam back at a 45° angle and pouring over the top of the foam then enough concrete surface is provided for tack strip fastening. This method requires a little extra thought. A few ideas to share when using this method is:

  1. Be sure to use the right “L-Block” or use other methods for the top course. The bearing part of the block (where the wall sits on the block) must only be the size of the wall. If it is wider than the wall then it pushes the foam needlessly further out into the room. Consider not using the “L block” and instead use brick or CMU brick. This allows the builder the flexibility to custom design the width and height of the stem wall to allow for the insulation and still achieve proper bearing and depth of concrete.
  2. Carpet installers frequently glue down tack strip. When using this method combine gluing with nailing.
  3. Be sure the installer pulls the tack strip as far away from the wall as the manufacture will allow.
  4. Doubling the tack strip in these areas works great. Again glue and nail.
  5. If the Builder does not like these ideas then furring the wall or using 2 x 6 or 2 x 8 studs is another option.

Slab Insulation Detail