How to Frame a Rec Room

Waterproof exterior walls. Tape a square-foot piece of plastic on the wall for 24 hours to see if it accumulates moisture. Seal walls with a good waterproofing paint to fill pores in the concrete if little or no moisture appears. Install a moisture barrier, either a waterproof membrane or foam board with a moisture-proof outside facing, if some dampness accumulates; serious water problems may require more extensive remediation.

Mark the outlines for the walls on the floor with a chalk line. Measure the distances for interior walls from the exterior with a tape measure and mark room corners with chalk. Measure from corner to corner to make sure the outline is square; if diagonal distances are identical, corners are square. Snap chalk lines on the floor 3 1/2 inches apart to make outlines for wall bottom plates.

Frame foundation walls with 2-by-2-inch furring studs and plates, fastened to the floor and wall with a hammer and concrete nails or a power screw gun and concrete screws and to the wood overhead joists with 16d framing nails. Space vertical furring studs with centers 16 inches apart, and toenail them with 8d galvanized nails driven diagonally into the top and bottom plates. Use a level to make sure studs are plumb.

Install rigid foam board insulation between the 2-by-2 studs. Secure this with construction adhesive or adhesive recommended by the manufacturer. Use foam with a moisture barrier on painted walls, with the facing toward the inside, but unfaced foam board on walls where a separate moisture barrier was installed. Never put two moisture barriers on the same wall.

Build interior rec room walls with 2-by-4-inch top and bottom plates and vertical studs. Assemble them on the floor and erect them or make them in place by nailing top and bottom plates to the floor and overhead joists and toenail studs into them. Make pre-built walls about an inch shorter than the height from floor to joist so they can be slipped into place. Drive tapered wooden shims between top and bottom plates of pre-built walls to fill the gap, and secure them at top and bottom. Space studs with centers 16 inches apart, and use a hammer and 16d framing nails to fasten them. Place walls between the marked lines and use a level to plumb all walls.

Frame a door in one wall. Set full studs the width of the door plus about 6 inches. Make a header to fit horizontally at the top of the required opening from two 2-by-4-inch boards sandwiched around a strip of 1/2-inch plywood cut to fit. Nail the header with framing nails through the side studs. Cut "trimmer" studs with a circular saw to go between the bottom of the header and the bottom plate to support the header; nail these to the full studs and the header.

Finish the door frame by cutting out the bottom plate on the inside edge of the trimmer studs with a reciprocal saw and by cutting short "cripple" studs to fit between the top of the header and the bottom of the top plate. Toenail the cripples to the top plate and header with framing nails.