How to Divide an Attic

Lay out the location of the dividing wall by measuring from one of the end walls in several locations across the floor of the attic and marking the floor with a pencil. Connect these marks with two chalk lines 3 1/2 inches apart to mark the two sides of the wall.

Install a 2-by-4 that will act as a bottom plate for the wall by placing it between the two chalk lines and screwing it to the floor with 3-inch-long screws.

Hang a plumb bob from the ceiling of the attic and adjust it until its point touches one edge of the bottom plate. Mark the point where the string touches the ceiling. Do the same with the other edge of the bottom plate. Do this at several different points along the bottom plate. Connect the marks that you made on the ceiling using a chalk line.

Attach a top plate to the ceiling in the same way that you attached the bottom plate to the floor. If you are dealing with a slanted roof at the top of the attic, attach the top plate directly to the slanted roof. If the top plate doesn't coincide with a rafter, add filler blocks between two rafters to which you can attach the top plate.

Lay out the locations for the wall studs by measuring along the bottom plate and making marks every 16 inches. These marks represent the centers of the studs. Hang a plumb bob from the top plate and make a mark directly above each of the marks on the bottom plate.

Measure the distance between the top and bottom plates at the location of these marks. For a slanted attic roof, you will have to cut each stud separately. Cut the studs to fit and install these between the top and bottom plates by driving 3-inch-long screws at an angle through the studs and into the plates.

Install drywall on both sides of the wall frame by measuring the space, cutting the drywall to fit and securing it the studs with 1 1/2-inch drywall screws screwed in every 12 inches along the length of the studs.

Apply spackle and drywall tape to the joints between drywall pieces and to the holes made by the screws. Allow it to dry, sand it with 100 grit sandpaper and a sanding block, then apply a second coat of spackle. Allow that to dry and sand it smooth.

Prime the entire wall surface then paint it with a coat of finish paint.