Frame an Attic Knee Wall

Knee walls define the usable space in a finished attic, turning awkward low-ceiling areas into storage and giving you clean vertical surfaces for insulation and drywall. The wall runs parallel to the ridge, typically 4 to 5 feet from the eave side, creating a boundary between standing height and crawlspace. Done well, a knee wall feels like it was always part of the house — plumb, solid, and ready for whatever finish you throw at it. Most attics need two knee walls, one on each sloped side, and the framing itself takes a weekend once you've settled on the height and run your layout. The real skill is cutting studs that marry a level floor to an angled roof. Every stud gets a different compound angle at the top, and your accuracy determines whether the drywall crew blesses or curses your name. This guide assumes you're working in an attic with exposed rafters and floor joists, standard 2x4 framing, and a roof pitch steep enough to give you meaningful headroom. If your attic floor isn't decked, lay down plywood first. You'll be walking that space hundreds of times before you're done.

1. Mark the wall line on the attic floor. Measure from the ridge beam down each rafter slope to find where 5 feet of headroom hits the floor — this is your rough wall location. Snap a chalk line parallel to the ridge at this point on both sides of the attic. Check that the line runs straight across multiple joist bays and doesn't wander. This line represents the face of your wall studs.
2. Cut and anchor the bottom plate. Cut a 2x4 bottom plate to run the full length of your wall line. Position it so the chalk line marks the outer edge of the plate, then screw it down into the floor joists below every 16 inches using 3-inch construction screws. If the plate spans between joists, add blocking underneath or shift the wall line slightly to land on solid framing.
3. Mark stud locations on the plates. Starting from one end, mark 16-inch on-center intervals along the bottom plate using a tape measure and Speed Square. Make a clear X on the side of each mark where the stud will sit. These marks ensure your studs align with standard drywall and sheathing dimensions.
4. Measure and cut the first stud. Hold a stud vertically at the first layout mark, tight against the bottom plate, and mark where it meets the underside of the rafter. Use a Speed Square to transfer the rafter angle onto the stud face, then cut with a circular saw. Test-fit the stud — it should sit plumb and meet the rafter snugly without gaps.
5. Cut remaining studs to fit the roof slope. Measure the vertical distance from plate to rafter at each stud location — this changes as the roof slopes. Transfer the rafter angle to each stud and cut. Work in batches of three or four studs, cutting and test-fitting before moving on. Studs should stand plumb when checked with a level.
6. Install studs and toenail to plates. Position each stud on its layout mark, check plumb with a 4-foot level, and toenail through the stud into the bottom plate with three 3-inch nails — two on one side, one on the other. Drive nails at a 45-degree angle. The stud should stand firm without wiggling.
7. Cut and install the top plate. Rip 2x4s lengthwise at the rafter angle to create angled top plates that sit flush against the rafters. Nail the top plate to the top of each stud with two 3-inch nails, then fasten the plate into the side of each rafter with 3-inch screws. This ties the wall into the roof structure.
8. Add blocking between studs at mid-height. Cut 2x4 blocks to fit horizontally between studs at roughly 4 feet up from the floor. Stagger them slightly so you can face-nail through each stud into the block ends. This blocking stiffens the wall, provides a nailer for drywall seams, and keeps studs from twisting.