8 Basic Steps to Successfully Insulate a Concrete Slab Floor

Posted by Andrew Oldroyd on February 15th, 2019

If your basement is unexpectedly chilly, then an uninsulated concrete floor might be the reason for that. Concrete floor insulation can save you a lot of money on your heating bills, making the garage or basement warmer. Using slab insulation services also provides the perfect foundation for finish flooring such as carpeting adding a fresh look.

Following are the basic steps to concrete a slab floor successfully:

1. The primary step is to prepare to insulate the floor. Here, the condition of the concrete needs to be evaluated at first, which can have issues such as moisture. You can also check the floor for smoothness and level. Grind down the significant high spots to ensure an even surface.

2. Measure the distance between the slab and the ceiling. It is a good practice to leave around 7 feet clearance between the ceiling and the surface of the finished floor. The subfloor can take up to 2 inches, and any floor covering can reduce clearance, so it is best to plan accordingly.  

3. To attain a robust concrete slab insulation, it is essential to clean the surface of the slab thoroughly. Then apply a coating of asphalt primer and follow label directions allowing it to dry thoroughly.

4. For areas prone to rainfall, concrete slab insulation service providers recommend using a fine-tooth trowel. The next step is to apply cold, cut-back asphalt mastic over the entire slab. Let it dry, then roll out 6-mil polyethylene sheeting over the floor to provide moisture protection. You can overlap the edges by 6 inches, allowing the sheeting to extend along perimeter walls. Get better results by walking over the plastic to increase adhesion. In climates where rainfall is light, the step involving cut-back asphalt mastic coating is not required.

5. Lay out pressure-treated sleepers at the edges of the room. Border their ends and fasten them to the slab with masonry nails.

6. Fit one and half thick rigid foam insulation between the sleepers. The strips should be about 12 inches wide. It is advisable to always measure for an exact fit to not fully compress the insulation. This can be a compromise on the performance.

7. Place a three-quarter inch of plywood sheet across the sleepers. Start with alternate rows with half sheets to move the joints. Use 2 inch long nails every 6 inches of the panel and every 12 inches into sleepers under panel centers.

8. This is the final step where once the plywood surface is laid out you can finish with the flooring material of your choice for the perfect concrete slab insulation.