How To Insulate A Concrete Floor
Written by Todd Fratzel.
Insulating Concrete Floors
If you live in a cold climate then you’re no stranger to cold concrete floors in the winter. If you’re planning on finishing a basement or portion of your home that has a concrete floor then it may be a good idea to insulate it before installing basement flooring. Concrete floors are cold and full of moisture that can be a long term maintenance problem.
Methods To Insulate A Concrete Floor
There are numerous methods for insulating concrete floors and slabs. The method that you chose really depends on cost and available headroom. If you’re finishing a basement most building codes require a minimum finished head room of 7′-6″. So any choice in the insulated sub-floor must account for that minimum height including the finished ceiling construction. The following are two methods that we’ve used in the past with great success.
Insulated Sub-Floor Panels
There are numerous products being sold today that are typically a combination of rigid foam insulation and some type of sub-floor material like OSB. There are quite a few of them on the market including Barricade Subfloor Tiles. The subfloor tiles are really great for folks with little DIY experience and clearance issues as they provide one of the thinnest insulated options.
If you’ve got adequate headroom and few interferences then this is the method that we like best. This method works great if you don’t have many doors and you can deal with the higher sub-floor at the stairs. The method is quite simple consisting of a layer of foam board insulation, sleepers and a plywood sub-floor (see diagram above).
- First you need to be sure the floor is clean. Be sure to fix any problems in the concrete floor such as cracks, spalls and water problems.
- Install a layer of rigid foam board insulation such as Styrofoam Tongue and Groove or Styrofoam Brand Highload 40 (depending on the loads you have the first one provides 25 psi and the second one provides 40 psi). We recommend at least 1 inch of foam board. Use a good quality foam board adhesive to adhere the foam to the concrete. If you’re interested in learning more about foam board insulating properties then check out our article on R Values Of Foam Board Insulation.
- Seal all the seams of the foam board insulation. We recommend you tape the seams with Tyvek (or similar) tape. You can seal along the walls with spray foam from a can (Great Stuff or similar).
- Install pressure treated sleepers. We recommend using 3/4″ thick pressure treated decking. Use foam board adhesive along the bottom of the sleepers and also attach the sleepers to the concrete using masonry nails or a powder actuated nailer.
- Install a layer of 3/4 inch tongue and groove AdvanTech (or other sub-floor material). We recommend you screw the sub-floor to the sleepers using stainless steel screws and sub-floor adhesive as well. We really recommend you consider using AdvanTech because of it’s excellent properties in damp environments.
- Finally install your finish flooring. You can install any type of flooring at this point because of the sturdy sub-floor.
Final Thoughts On Insulating A Concrete Floor
The only issue to watch out for in this situation is the height. You’ll most likely end up with 1 inch of foam board, 3/4 of an inch sleepers and 3/4 of an inch for the sub-floor for a total of 2-1/2 inches. This will most likely require doors to be lifted and stairs to be reconfigured. However, you’ll have a very warm comfortable floor and a whole lot less moisture in your basement.
Want To Hire A Professional?
If you’re feeling a bit overwhelmed by a full basement remodel then you may want to consider hiring a contractor. A good place to start is using industry proven contractor referral companies. Company like ServiceMagic offer a great referral service. Just follow the next link:
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