Most interior details, mainly walls and closets, are built with 2x4s.
- Mark the centerline of the new wall across the ceiling. At each end of the line, measure and mark half the width of the new wall's top plate in one direction. Snap a chalk line between these marks. Plan one stud at each end and, from the end that meets a wall, measure 151/4 inches to locate the inside edge of the first intermediate stud, then 16 inches to the same edge of each additional stud.
- Lay the top and bottom plates side by side on the floor. Measure where each wall stud will go and mark with perpendicular lines across the plates, using a combination square.
- Locate the joists in the ceiling and hold the top plate in position along the guideline marked on the ceiling and nail through the ceiling material and into each joist with two 3 1/2-inch nails.
- Use a plumb bob (string with weight) from each end of the top plate on the ceiling to just above the floor, then mark the floor to establish the bottom plate's location directly below it. Snap a chalk line along the floor between the marks as a guide for the bottom plate's edge. Nail the plate with 3-inch nails staggered and spaced every 16 inches.
- Install the studs and check plumb using a carpenter's level and nail into place.
- Where one wall intersects another, double-up studs.
- If the wall will turn a corner, frame with two full-length studs that have blocks sandwiched in between