What Materials Are Needed for a 12' x 28' Flat Roof?

Joists

• Joists are supporting members of a roof that runs horizontally from wall to wall. Timber or steel joists serve as the foundation for a roof. Use joists that are long enough for both ends of the joists to reach the outer edges of the walls' frame. For 12-foot by 28-foot ceilings, 12-foot long joists are more readily available for purchase than 28-foot long joists. The joists should be approximately 12 to 24 inches apart from the center of each board; the appropriate length depends on how much weight the roof is expected to support.

Noggins

• Noggins are small spacers used to keep joists from moving out of place. Insert the noggins before covering the joists up with plywood. One method of inserting noggins is doing so while laying the plywood on the joists. This method allows the roof builders to have a platform on top of the roof while inserting the noggins.

Plywood

• Cover the joists with 5/8 or 3/4-inch plywood. Also, make sure an approximate 1/8-inch gap is between the edges of each sheet in case the plywood expands or contracts. Other materials may be used to cover the joist, including sheet metal, but plywood is more inexpensive than other types of material. Plywood consists of several, tightly compacted layers made up of wood grains. The most common plywood sheets available are 4-feet by 8-feet. Use a table saw to make any necessary cuts to the plywood sheets

Rubber

• After laying down all the necessary plywood, cover the sheets with a layer of rubber. Use a utility knife to make cuts to the rubber. Make sure you have enough rubber to cover the roof's 12-foot by 28-foot frame. Allow extra rubber to hang over the roof. Apply glue underneath the rubber where it meets the edge of the roof. Once the glue dries, cut the overlapping rubber. The rubber is meant to prevent water from leaking into the roof. Make sure all debris is swept off the plywood before covering the sheets with rubber.

Pneumatic Nail Gun

• Use a pneumatic nail gun for nailing the joists to the walls and plywood to the joists. A pneumatic nail gun relies on pressurized air to apply nails to the wood. If you cannot afford a pneumatic nail gun, use a hammer and nails to attach joists and plywood. Screws are another option for connecting joists and plywood; use a power drill to implement screws.