How to Frame a Pressure-Treated Basement

Moisture-proof exterior basement foundation walls before beginning any framing. Tape a foot-square piece of plastic on the wall and leave it 24 hours to see how much moisture collects. Seal the wall with a good waterproofing paint if there is little dampness; install a moisture membrane if there is significant moisture.

Buy lumber rated for basements -- a type specified for use in moisture situations where there is no contact with soil. Get hot-dipped galvanized nails for fasteners; the copper-based treatments will corrode conventional nails. Frame exterior walls with either 2-by-4-inch studs and plates or 2-by-2-inch furring strips; stud walls allow for more insulation, whereas furred walls provide a bit more space.

Frame exterior walls by nailing top and bottom plates to the floor with concrete nails and to wood ceiling joists with 16d framing nails and a hammer. Set vertical studs or furring strips with centers 16 inches apart and fasten them to top and bottom plates with toenails driven diagonally through studs and into the plates. Put fiberglass insulation inside stud walls and rigid foam inside furred walls. Use unfaced insulation if a moisture barrier was installed.

Mark the outlines for interior walls, using a tape measure to locate spaces and a chalk line to snap lines on the floor to locate the bottom plates. Square the space by measuring from corner to corner and adjusting the outlines until those diagonals are identical, so the corners will be 90-degrees. Use a level when fastening walls vertically to make sure they are plumb.

Build interior walls with 2-by-4-inch studs, either made on the floor and erected or built in place. Frame walls on a floor by nailing studs through top and bottom plates; cut studs with a circular saw about an inch shorter than the distance between floor and ceiling. Make in-place walls by nailing top and bottom plates to joists and the floor and toenailing studs to the plates.