Do I Really Need Knee Walls In My Attic?

One question that many homeowners end up asking is “do I really need knee walls in my attic?” If you went around to 100 different homes built within the past decade, you would probably find knee walls in roughly half of them. Some builders go the extra mile by installing them, while others don’t. In order to answer the question, we must first look at the function of knee walls and why they’re used.

What Are Knee Walls?

Knee walls are short, usually wooden, walls installed around the sides of an attic where the rafters meet the floor. You can see the image below for an example of a knee wall. In most instances, they are no taller than 3 feet, but some builders may custom fit them according to the roof’s shape and size.

If you aren’t sure whether or not your attic contains knee walls, go and look around the edges.¬†Basically, triangular shaped attics do not feature knee walls, while attics with a more “boxy” shape do.

attic-knee-wall-01
Illustration of knee walls in the attic.

Provides Greater Stability

One of the benefits to using knee walls in the attic is the increases stability they provide. Once installed, they’ll support some of the weight from the rafters. It’s not uncommon for builders to place them up against the rafters while working on the roof. Once the roof is complete, they may take the knee walls down or leave them up.

Knee walls aren’t technically required for a structurally sound home or building, but they do take some of the load off the rafters. If you live in an older home and are concerned about the roof’s stability, it might be a good idea to install them.

Better Insulation

Knee walls also provide “pockets” for additional insulation in the attic. If you go back and view the illustration above, you’ll notice there’s an enclosed area behind the knee wall. Rather than leaving this space empty, homeowners can fill it with insulation for additional thermal protection.

Filling the space behind the knee walls with insulation helps to lock in your home’s thermal energy. With that said, it’s important to allow outdoor air to enter the attic. We discuss this in greater detail in a previous blog post about baffles.

What do you think about attic knee walls? Let us know in the comments section below!

Leave a Comment