Plan out your project determining your budget, the size of the addition, materials, tools you'll need, necessary permits and a step-by-step construction plan. This will help you save money and avoid future frustrations.
Design your addition so the new roof attaches under the lip of the existing roof. The minimum ceiling height and window area required by the local building codes will help determine new room details. A new bathroom addition should be located near the existing plumbing drainage and water supply.
Excavate for the foundation using a tractor if available and make wood forms to pour the concrete into, according to the approved construction specifications. The footings should be at least three feet underground if building in a frost zone and should have embedded bolts to secure the sill plates.
Attach wood sill plates flat onto the top of the concrete foundation using the embedded bolts. Nail wood floor joists standing on end every 16-inches onto the sill plates. Allow room at the ends of the joists to nail on the rim joists.
Nail down 3/4-inch plywood sub-flooring onto the floor joists. Build 2-by-4 walls with 5/8-inch thick CDX plywood facing, lift them into place and then brace the walls using 2-by-4 studs nailed at 45 degree angles until the walls are all nailed firmly in place and the roof joists are affixed.
Hammer down roof joists onto the tops of the 2-by-4 walls spaced every 16 inches and nail 5/8-inch CDX plywood onto the roof joists. Nail down roofing paper with roofing nails, as well as the final layer of asphalt shingles.
Nail siding onto the exterior and affix insulation inside the wall as desired. Finish the interior with gypsum board, wood trim and the desired flooring materials.
Things You Will Need
- 16d framing nails
- Plywood for forms
- Joist lumber per specifications
- 3/4-inch interior plywood
- 5/8-inch exterior plywood
- 2--by-4 lumber
- 1/2-inch roofing nails
- Instead of new framing, consider the option of simply adding on a prefabricated addition, which will save time and may be less expensive in the long run.