Attic Knee Wall Construction
You can see the image below for an example of a knee wall.
Attic knee wall construction. The bottom plate of the knee wall rests on top of the floor joists leaving a large pathway for attic air to come up into the air cavity of the knee wall. Scribe a line on your scrap piece along the angle formed by the rafter. Framing basics for attic knee walls along the sides of your loft or attic space. The knee wall will be built on the floor of the attic and then tipped into place against the rafters.
Knee walls are short usually wooden walls installed around the sides of an attic where the rafters meet the floor. When insulated and covered with drywall the walls improve the thermal envelope of an attic. A knee wall is a short vertical wall roughly two or three feet high that blocks in that useless triangular space. Install a top and bottom plate or blocking at the top and bottom of all knee wall cavities.
Determine the angle of rafters by setting the scrap piece of 2x4 in a vertical position against the side of a rafter. But you do so at the expense of floor space. The higher the knee wall the greater the amount of useful wall space you create in your finished attic. Secondly without an air barrier on the back of the knee wall and with the potential to sag as indicated above attic air goes around the insulation into the cavity on the vertical space as well.
What are knee walls. Support and follow me. Knee walls are short wood framed walls that install between the ceiling joists and rafters in an attic. 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.