Building Attic Kneewalls

Attic kneewalls, short walls that reach from the floor of an attic to the rafters, can provide a nice dimension to attic rooms and actually make them feel less cramped. Most attic kneewalls are five feet (1.5 m) tall, the minimum ceiling height for usable floor space in most building codes. This also means that not too much floor space is wasted.

The unfinished space behind attic kneewalls can actually serve a purpose also. This space can be utilized for built-in storage, and for hiding service lines. To use this space, you should build a framed opening in the attic kneewall during the framing process, just like you would frame an opening in a wall for a window or door.

To build an attic kneewall, you will need a circular saw, a chalk line, a level, and a T-bevel. In addition, you will need 2 x 4 and 2 x 6 lumber, and nails. Attic kneewalls are much like partition walls, with the addition of beveled top plates and studs which are cut at an angle and follow the slope of the rafters. A 2 x 6 top plate is needed for the added stud depth created by the angled cut.

Using a straight 2 x 4, cut the board so that it is a few inches longer than the height of the proposed wall. Measure the exact height of the wall and draw a line across the board where the wall height is. This is your storyboard.

At the end of the attic, set the storyboard flat against the outside rafter. Use a level to check the storyboard and make sure it is straight, and align the height mark with the bottom edge of the outer rafter. Mark the rafter at the spot where the mark on the storyboard hits the rafter. Next, mark the front edge of the storyboard onto the subfloor. These marks will show you where the top and bottom wall plates will be.

When building attic kneewalls, the storyboard must be perfectly plumb, and should be periodically checked with a lever. Trace along the bottom edge of the rafter so that the rafter slope is transferred onto the storyboard. Repeat the entire process on the other end of the room. Use a chalk line to line up the marks and mark along the rafters and along the subfloor.

Next, use a T-bevel to match the slope of the rafters which is marked on the storyboard. Use the T-bevel to adjust a saw blade to the correct angle, and bevel-cut one edge of the 2 x 6 top plate. You have now cut a beveled edge on the top wall plate of the attic kneewall.

Mark the stud locations on each of the wall plates. Install the wall plates along the chalk lines and nail them to the floor joists and rafters. Measure each stud and cut to fit, making sure you angle-cut the top end so that it meets the top plate. Nail each stud in place. The framing for the attic kneewall is now complete.

After the framing is complete, plumbing and wiring systems should be installed, as well as drywall. In many attics, insulation is not installed behind the kneewall. Adding insulation can make the attic a much more pleasant place as well as reducing heating and cooling costs.