Monday, January 26, 2015

Roof Trusses



All about Roof Trusses

A Common Residential roof truss is made up of 5 parts. 
1. The Roof Rafter on which roof sheathing and finally roof surface is attached
2. The ceiling rafter on which the ceiling surface is attached
3. Bracing tying the two elements together into geometric supporting structure.
4. The Truss Tail which is the extended portion of the roof rafter protruding past the wall creating an overhang.
5. Connection plates which are steel plates with barbs punched one way through the plate, creating a connection of two members when this plate is forced by machine into the surface of the two members.

Since local energy code requires about 12” of insulation in our area (using batt style) to meet the minimum R-38 requirement we have to examine how different kinds of trusses affect this ability to insulate (mainly over the wall where the two members meet). Ever see ice dams on the eaves of houses?  The Economy truss is the main cause.

Common Residential Truss types (3) shown
Left: Economy Truss (poor): has the minimum amount of wood required to attach the two members
Center: Max Butt Truss (better): Raised heel gives more height for insulation
Right: Energy Truss (best):Raised heel gives full height for insulation

Note: raised heel trusses are more expensive.