Insulate Under Stairs

By Todd Fratzel on Basements, Insulation

Insulate The Bottom Side Of Stairs

Effectively insulating a house isn’t rocket science but there are a few areas that folks forget to account for which can result in quite a large amount of heat loss.  Some areas that get overlooked include; insulating attic stairs and properly insulating basement walls. The other are that is often overlooked is the bottom side of stairs that have un-heated space below them.

This is a problem that I even overlooked in our new home. I say that with a grain of salt because the reason I overlooked it is fairly simple. Originally we planned on keeping our basement heated but the reality is we haven’t finished the space yet and there is no reason to heat it until the space is being used. As a result there are many really cold winter days that this beautiful staircase feels very cool on our feet especially after stepping off our warm radiant heated wood floors.

How To Insulate Under Stairs

Insulated the bottom side of stairs is actually pretty straight forward. In our case it’s a bit more complicated because the drywall has already been installed below the staircase as you can see in the adjacent photo. However, the following process is the simplest way to insulate the bottom of stairs.

  • Install 1×3 wood strapping along the bottom of the stair stringers from the bottom up to the top. The strapping will give you something to attach the insulation to and also drywall if you’re going to finish the surface.
  • Install 1 inch or 2 inches (depending on how cold your climate is) of foam board insulation (see foam board insulation R values). I recommend you use either extruded polystyrene or foil faced polyisocyanurate foam insulation. The easiest way to install it is with screws and large fender washers. You can also use foam panel adhesive.

For our situation we may just install a layer of foam board directly on top of the existing drywall and then drywall over that again. It’s probably much easier than tearing out the old drywall first. The bottom line is insulating the bottom of your stairs is an easy way to ensure your house is insulated properly and not wasting energy.

About the author

Todd Fratzel

I'm full time builder for a large construction company in New Hampshire. I run their design-build division that specializes in custom homes, commercial design-build projects and sub-divisions. I'm also a licensed civil and structural engineer with extensive experience in civil and structural design and home construction. My hope is that I can share my experience in the home construction, home improvement and home renovation profession with other builders and home owners. I'm also the Editor-in-Chief and Founder of Tool Box Buzz. Please feel free to contact me if you have any questions, suggestions or you'd like to inquire about advertising on this site.

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