A Guide to Roof Framing - Prefabricated or Conventional

The thought of framing a roof is a nightmare for most carpenters. Framing a roof is one of the most difficult projects to undertake in construction, however it is also one of the most fulfilling. The thought of a general contractor using trusses on a house, just does not agree with my set of values. I personally do not approve of trusses being used in construction as of yet. Simply because most building codes allow trusses to be placed on 24 inch centers. Conventional framing is required at 16 inches on center. Conventional framing is my favorite by far.

Trusses are prefabricated meaning they are built to the specifications according to the blueprints specs, live load, dead load, etc... The problem with trusses is they are rated per specs at 24inches on center, that leaves 22.5 inches in between. The problem arises somewhere between 3 to 7 yrs later, you will start to see a sag between the trusses. This is not the trusses sagging but the plywood used for your roof, unless a thicker grade plywood was used 3/4 inch or more,which I highly doubt. The standard thickness for plywood is 1/2 inch, with the seams nailed every 3 inches on center alternating and 4 inches on center on your 24 inch centers. The results are you end up with a 4 foot x 8 foot x 1/2 inch piece of plywood spanned across 5 trusses with 4-22.5 inch spaces in between each truss. You will have approximately 18 to 20-8d nails on each end and 12 to16 nails in the three trusses in the center.Total you will have 72 to 86 nails per sheet of plywood.