Ceiling Joist Roof Rafter

Roof rafters don t need to be parallel to ceiling joists when rafter ties are used.

Ceiling joist roof rafter.

Pictured at left is a 2x6 rafter spliced together using 3 4 plywood. In this case the rafter as a whole is actually stronger than it would have been because the splice is more than adequate and the plywood adds to the strength. The are similar to trusses in this regard. In unfinished space an attic insulation is typically laid between the joists.

The rafter tie is attached to the top of the rafters such as the topmost point in a cable or hipped roof. If you are framing a cathedral ceiling there are a couple ways to deal with the need for rafter ties. This board forms the bottom member of each rafter and of course the ceiling of the space below. They are nominally 2 inches thick actual width usually 1 1 2 inches and come in a variety of widths from 8 to 12 inches.

As a general rule roofs that have a high human occupancy rate should be framed with rafters every 16 structures such as sheds or barns can be frames with rafters every 24 again make sure to consult local codes. Joists are traditionally made from timber. Rafter ties help tie the roof rafters together structurally eliminating the need for ceiling joists. In this design the tops of the rafters attach to a load bearing ridge beam that runs along the length of the roof.

You can possibly remove them altogether of you include posts in the gable walls to support a structural ridge. A structural ridge is the standard alternative to ceiling joists. In this case the framer just needed a longer rafter. Ceiling joists can serve as rafter ties to resist outward thrust on the walls from the rafter loads if they are installed parallel to the rafters and in accordance with code.

Rafter ties or ceiling joists acting as rafter ties are required by code unless the house is designed so that the walls or a structural ridge beam carries the full load of the roof. If your project had a rafter length of 8 or less a safe and strong method is to use 2x8 framed 16 on center. Joists are the parallel horizontal beams that run across an open space joining opposite walls in a building to support both the ceiling below and the floor above.