Finish Your Attic: How to Build Attic Walls, Part 1

What You'll Need
Tape measure
2x4-inch lumber
Miter saw

If you are undertaking an attic conversion, you will probably be adding some walls. Finished attics often have small dividing walls that block off the lowest part of a triangular roof, separating the inside of the attic from drafts and moisture. Knee walls provide the perfect way to turn an old, abandoned attic into a useful extra room that can serve as a bedroom, office, or other living space.

In Part 1 of this guide, you will learn how to measure the roof and rafters to find the correct location for the walls, cut off the plates for the walls, and create studs to fit those walls. In part 2, you will learn how to fit these to the attic wall and finish them well.

Caution: In many jurisdictions, it is illegal to use attic space as living space. Consult your local building code and inquire about any necessary permits before beginning any such project.

Step 1—Measure the Attic

To build your walls to the correct length, measure the angle of the rafter by laying a piece of 2x4-inch lumber against the side of the rafter in a vertical position. Mark the line that the angle forms along your 2x4. Use your saw to cut along this line. You now have a template of the rafter angle.

With your tape measure, work out the position of the timber against the top and bottom of the attic and also calculate the length of wood you will need to create the tops and bottoms of the rafters.

Step 2—Cut the Lumber

Before you can use your template to make the studs for your wall, you need to cut the top and bottom plates, which will serve to support the wall. Get some large pieces of 2x4-inch lumber. Measure out enough to cover the length of the rafter onto which you will be fitting the wall, take the first piece of lumber over to the miter saw, and cut it down so it fits tightly into the wall. You may need to nail several pieces of your wood together.

These plates support the wall. Make them large enough to cover its entire length. Make sure they are laid out straight against the wall before you begin cutting.

Step 3—Cutting the Studs

The studs for the wall go in between the sole plates and help support the drywall. Measure each of the studs out carefully and then cut the top and bottom of the stud timbers until you can slide them into position against the sole plates. A sloping joint would probably be best for this.