If you need to add a rumpus room, home office or workshop to your home, remodeling a basement is a practical way of gaining extra space without altering the roof line by extending your home with an addition. Since most basements have a concrete floor, the tricky part is fixing the partition wall sole plate correctly.
Locate and mark the position of the floor joists above the basement with an electronic stud finder and pencil if the basement is fitted with a ceiling.
Plan the layout. If your partition wall runs parallel to the joists, either position the partition wall so that the head plate can be attached directly to a joist or strip of the ceiling and install 2-x-4 noggins at right angles between the joist, to provide an anchor for the head plate at the desired location; space the noggins on 16-inch centers between joists. Attach the head plate to each individual joist at the location of your choice, if the joists run at right angles to the partition.
Measure and mark the location of both ends of the head plate with a steel measuring tape and pencil. Cut a 2-x-4 head plate to size on a miter saw set at 90 degrees.
Position the head plate accurately and secure it to the middle joist with the wide face upward. Hammer a single 16D coated sinker nail through the head plate and into the middle joist or into the central noggin, whichever is applicable.
Move to the left-hand side and align the head plate at 90 degrees to the side wall with a large builder's square. Once aligned, secure the head plate to the end joist with two 16D coated sinker nails. Move to the other end of the head plate, align the plate with the square and secure it to the joist with two nails as described previously. Repeat by securing the head plate to all remaining joists with two 16D nails in each joist or to the noggins spaced 16 inches apart, whichever is applicable.
Drop a plumb line down to floor level from one side of the head plate at each end and mark the sole plate position on the floor with a felt-tip pen. Snap an accurate chalk line between the two marks to act a reference point.
Align the edge of the sole plate with the chalk line. Drill a pilot hole through the center of the sole plate and into the concrete floor, 2 inches from the left end with a hammer drill fitted with a 3/16-inch masonry bit. Push the sole plate to one side and enlarge the floor pilot hole with a masonry bit sized to accommodate a 3/8-inch concrete anchor.
Insert a concrete anchor into the prepared hole, enlarge the pilot hole in the sole plate and snug the sole plate to the floor with a masonry anchor bolt and socket wrench, without overtightening.
Move to the other end of the sole plate and anchor it loosely to the floor as described before; you may have to undo the anchor bolt on the far end after drilling your 3/16-inch pilot hole. Once the right-hand anchor is installed, secure both ends of the sole plate to the floor with anchor bolts.
Mark the stud positions on the sole plate spaced apart on 16-inch centers; you may have to adjust the gap between the two end studs so that the central studs are 16 inches apart. If you intend to add an intervening door to the partition, position a suitable door frame in the required place between two studs and attach a second stud to the outside of the frame to turn it into a "king" stud. Add a couple of evenly spaced "cripple" studs above the frame header when securing the studs to the head and sole plates in a later step.
Measure the distance between the head plate and the sole plate with a steel measuring tape. Add 1/16 inch to this measurement, transfer the measurement to sections of 2-x-4 lumber and cut a suitable number of studs to size on a miter saw set at 90 degrees; the extra 1/16 inch will allow you to wedge the studs firmly between the sole and head plates prior to nailing.
Attach the end studs to the adjacent walls with 16D nails into suitable noggins or studs located with the stud finder. Drive two nails between the stud and sole/header joints at a 45-degree angle from the room side of the studs.
Position the remaining studs between the head and sole plates by wedging them into place. Once positioned, place a long spirit level vertically against the stud, center the bubble by tapping the bottom of the stud either way with a hammer and secure the stud to the sole plate with two opposing 16d nails hammered into both sides of the stud and into the sole plates at a 45-degree angle.
Secure the studs to the head plate by repeating the steps described before.
Brace the studs with three horizontal 16-inch-long 2-x-4 noggins spaced evenly apart between the studs on each evenly spaced gap. Stagger noggins evenly between the opposing noggins in the odd-spaced gaps; secure the noggins to the studs with two opposing 16D nails driven in at a 45-degree angle. If applicable, secure the door frame to the studs with three pairs of 16D nails on both sides of the frame and across the door header noggin.
Finish the wall by cladding both sides with drywall panels secured to the studs with drywall screws and a cordless power screwdriver; butt each horizontal and vertical joint firmly together without leaving gaps. Cover the joints by taping and floating drywall tape to the joints with drywall compound and a drywall float.
Smooth all joints down with sandpaper and a sanding block after the drywall compound has dried; your partition wall is now ready for a coat of paint.