Mark the location on the attic floor for the bottom plate. If your joists are exposed, it is a good idea to put a ¾-inch plywood floor down first on top of the joists. When you lay out the location of the bottom plate, make sure the line for the plate is parallel to the exterior frame of the building. Then chalk a line that runs the full length of the knee wall. This is where your wall will go.
Cut a two-by-four to length and nail the board in place along each chalk line. You can use several boards, if the knee wall runs the length of the attic. Use No. 16 framing nails to attach the two-by-four bottom plate to the floor joists. Make sure that the bottom plate is nailed to each floor joist that it crosses. It is a good idea to end each wall directly underneath a roof rafter. This makes the task of framing the side walls much easier.
Place two vertical framing members (two-by-fours) at the each end of the bottom plate. These pieces will not be part of the wall, but instead they will be used as guides to place the top plate, which is tied directly to the roof rafters. Set the bottom end of the two-by-four next to the plate (but not on top of it) and drive one framing nail into it, so as to hold it in place temporarily. Attach the top of the vertical framing piece to the rafter. Make sure this board is plumb by using a 2-foot level. Then chalk a line across the rafters from one end of the knee wall to the other. If the length of the knee wall is longer than the length of one board, then you will need several vertical pieces. Don't forget that all the temporary vertical studs must be plumb and that the bottom edge of each stud must butt up against the bottom plate.
Install the top plate for the wall to the roof rafters with more framing nails. Let this piece (or pieces) butt up against the temporary vertical studs. Nail each two-by-four with a couple of No. 16 framing nails.
Take down the temporary vertical pieces and start adding the vertical studs of the knee wall. These should be 16 inches on center, and the top end of each piece will have to be cut with a bevel gauge so that it fits underneath the top plate. Nail each vertical piece with several No. 16 framing nails at both the top and bottom.
Things You Will Need
- Measuring tape
- Chalk line
- Circular saw
- Carpenter's square
- Safety glasses
- 2-foot level
- Bevel gauge
- If you plan to place batts of insulation in the knee wall, you can always build the wall from two-by-sixes or two-by-eights for greater insulation value.