The normal interior wall is made of a frame of vertical two by four studs. These rest atop a base made of 2 by 4 and a top plate. Walls which will contain a lot of plumbing (a “wet wall”) should be made of 2 by 6 lumber. The frame is then covered with the appropriate material .
The first step is to make sure the area is clear. Carpet and drywall need to be cleared from the floor and ends of where the wall is going to go. If the new wall will not abutt to the connecting wall, or if it will not be directly under a ceiling joist, nailing blocks have to be installed between the framing pieces.
Once the floor, connecting walls, and ceiling have been cleared and the studs and joists exposed, it’s time to mark a centerline for the new wall across the ceiling. At each end, mark out half the width of the top plate in one direction. Then make a chalk line from end to end between the marks. The next step is to mark the locations of the wall studs.
This is done on the top and bottom plates. They need to be laid side by side on the floor. The first stud (besides the one you plan on having meet the wall) should be measured 15 ¾ inches from the end of the new wall, and hence the plates. After that, measure 16 inches and mark the locations for the inside edge of each succeeding wall stud. These marks will denote the edge of the stud closest to where you started, not the center of the stud. Do this very carefully, making a line all the way across each plate using a square to ensure that each stud mark is in perfect agreement.
Now it’s time to put the top plate in place. First, find the ceiling joists using a stud locater or by making careful measurements. Place your top plate along the chalk line made earlier, and nail it into the ceiling joists using two 3½” nails at each one. In cases where the new wall runs parallel to the joists, nailing blocks must first be installed between the joists and the top plate is nailed to these.
Now use the top plate to locate the position for the bottom plate. Gravity gives a big assist here with the ancient plumb bob. Attach it to the top plate’s edge in order to find the location of the edge of the bottom plate. Mark this postion in at least two places toward the ends of the top plate, and then use a chalk line to snap a line between them. Now the bottom plate’s position is clearly marked. Nail it in place using 3½” nails staggered every 16 inches or so.
Finally, the studs are installed. Stand them on the bottom plate and raise them into position at the marks made earlier. Check them with a carpenter’s level to ensure that they are vertical, and use stud framing clips if available to secure them in place. 2½” nails can also be used to toenail the studs in place. Be sure to double up the studs where one wall meets another.