Thickness Of Insulation Under Concrete Floor

There will be a damp proof membrane under the insulation and possibly a second membrane on top depending on the type of screed.

Thickness of insulation under concrete floor.

In this scenario a rigid foam insulation is usual and as you d want the same u value in the roof we need the same thickness of insulation 180mm. Step 4 place 2 inch thick pieces of rigid styrofoam insulation on top of the plastic sheeting. The first important thing to pay intention to is the depth of the floor slab. On the other hand if you are laying insulation on top of the existing slab than you will need to make sure that there are no construction.

Many increase the under slab insulating foam board thickness to 3 or 4 inches at the outer 2 to 4 feet of the slab. In cold climates it is advisable to use a minimum of 2 inches of extruded polystyrene under the slab. Depending on the use of the building the slab can then be finished ready for use or receive a screed suitable for a floor finish. A 50mm thick layer of proprietary floor slab insulation is usually enough to reach and maintain the target u value but this should be checked with an architect first.

The math is pretty simple the thicker the concrete floor insulation material the deeper the slab will have to be. Designers generally insulate both directly under the slab and around the perimeter as well. Place the insulation edge to edge using duct or other construction tape to hold the insulation together. Insulation sheets should be laid tightly together with the joints staggered to avoid movement.

Insulation is laid on the concrete and covered with a screed. Namely if you are only digging the slab you will need to take into account the thickness of the insulation since it will affect the depth of the slab.