How to Frame an Addition

Lay your foundation. Whether you plan on pouring concrete or building a raised sub-floor, your floor--or footprint--comes first.

Lay out your walls by marking on your floor exactly where your doors and windows will go. Around the exterior of the foundation, you will snap a line, using a chalk box with string, to make sure the walls are straight.

Determine your maximum wall height, then cut all of your studs 4 1/2 inches shorter than the length you determine. The bottom seal plate is 1 1/2 inches and the double top plate is 3 inches. This is 4 1/2 inches that must come off of your studs to ensure an accurate room height.

Make a template so you know exactly where to nail your studs. Do this by tagging two two-by-fours together using 8-penny nails. Mark on both pieces exactly where you will place your studs.

Spread the two-by-fours apart so you can lay your studs between them. You now have accurate and matching stud marks on the top and bottom plates so you can begin building your walls.

Using 16-penny nails and a nail gun, construct your room addition walls while they are laying down. Follow your bottom and top plate templates, and nail the studs where you placed your marks using a minimum of two 16-penny nails on each end. Lift the walls into place.

Make all your walls the same way, starting with a template, marking your plates and then nailing in the studs. Some room additions will require two walls, and some three. Most additions will already have at least one existing wall.

Secure the walls with plenty of nails. Add braces for extra support. These angled pieces of lumber also ensure that the walls are plumb.

Go back and put in any jack studs, king studs, headers, fire blocking and cripples. These are all extra two-by-fours used when framing a window or door rough opening to add strength and support to the structure.

Place the headers horizontally across the top of the windows. Jack studs run the length of the window from floor to ceiling on each side of the window opening, and cripples are small blocks that fit vertically between the header and the top plate.

Attach a king stud to each side of both jack studs for additional support. Some local codes require fire blocking, or placing small blocks between the king studs and the nearest framing stud on both sides.

Nail down your final top plate all the way around the walls on top of the existing top plate. All top plates are doubled. Place all of your nails in line with the studs below.