How to Separate Rooms With a Wall

Move a stud finder along the ceiling to locate ceiling joists. If the joists are running at 90 degrees from the direction of your new wall, you can locate the wall where you want. If the joists are running parallel with the direction of your new wall, position the new wall directly under a ceiling joist. Mark the location of a parallel ceiling joist on both ends of the room and draw a straight line between them so that you can position your wall exactly under the joist.

Measure the length of your new wall. Cut two 2-by-4 boards to this length using a table saw. Use a rotary trim saw to remove crown molding where the board will mount to the ceiling. Line up one board on the ceiling using your line as a guide. Screw the board into the ceiling joist using 3-inch screws and a screwdriver. Use two screws every 12 inches. Line up the second board with the first and screw the two boards together.

Measure the width of the 2-by-4 dividing the 3 1/2-inch side in half. Draw a line along the center of the board running the length of the wall. Drop a plumb line from the center line to find the center line directly below the ceiling board. Mark the flooring. Repeat every 2 feet along the length of the new wall so that you have a line of marks on the flooring.

Use scrap 2-by-4 to draw a line on the flooring and up the wall a few inches on each end. If you have carpet and padding, center the scrap 2-by-4 on the line and use the straight side edge and cut the carpet and pad with a utility knife. Cut 1/4 inch wider than the board on each side of the board. Remove the carpet and pad. Use a rotary trim saw to cut through the baseboards at the same measurements.

Measure the length of the wall at the floor. Cut a 2-by-4 board to length. Screw the board into the subfloor using 3-inch screws and a screwdriver. Measure the height of the wall between the top plates and bottom plate. Cut a 2-by-4 board to fit. Position the stud against the existing wall.

Toenail or screw the stud to the top and bottom plates using a framing nail gun or screws and a screwdriver. "Toenail" means to nail at an angle through the stud into the plates. Measure the thickness of the stud and divide in half. Measure 16 inches from the center mark. Make a mark on your bottom plate; 16 inches is the required spacing between wall studs. Measure for the stud. Cut and install the stud. Repeat across the wall with your last stud positioned flush against the existing wall.