Roof Trusses

An unusual project with an uncommon shape presented the kind of design challenge truss technicians don’t see every day.

When Jim’s Apple Barn, the largest candy store in Minnesota, wanted to expand by way of adding a confection-filled planetarium to the end of a blazing yellow barn already bursting with sweets, it had a difficult time finding a truss company willing to take on the project. “We were the only ones that said yes,” recalled Trevor Ebinger, a member of the Manion Lumber & Truss sales staff. “It was quite an undertaking.”

A little forethought can prevent the potential overstress that occurs when deflection leads to rooftop ponding.

The BFS design team in Shelby, Alabama “collaborate on anything that doesn’t sit right,” says Thom Patton. One result: a roof that rests perfectly on a school building after a simplified build and easy install process.

This Research Report will look specifically at the sill plate requirements according to the 2009, 2012, and 2015 International Residential Code (IRC) and International Building Code (IBC) and clarify if a sill plate is required in the following conditions:

  • Flat truss bottom chord bearing on ICF wall.
  • Flat truss top chord bearing on ICF wall.
  • Roof truss bearing on ICF wall.

Lumber Design Values

No matter the species, component manufacturers (CMs) purchase and rely on the accuracy and reliability of many different lumber design properties, including: bending (Fb); shear parallel to grain (Fv), compression perpendicular to grain (Fc^), compression parallel to grain (Fc), tension parallel to grain (Ft), and modulus of elasticity (E and Emin).

Some truss lumber repair nailing patterns call for 16d common nails. Most nail guns do not support 16d nails, but have an equivalent to a 12/10d nail. Is there a substitution guide or ESR report that could help us?

I recall seeing a design recommendation several years ago regarding installation of hanger nails above the neutral axis of the bottom chord of a plated girder truss. The intent was to avoid dumping large loads into the bottom chord, below the neutral axis. Can you tell me where I can find this information?

If you use hurricane clips to secure roof trusses from uplift, are you allowed to use fewer than the typical three nails in the bearing heel of the roof truss? I am concerned because we want to do the right fastening schedule, but three nails in addition to the hurricane clip splits the wood. What is the standard recommendation?

What is the correct method of attaching scissors trusses to the top plate? I read recently in a trade magazine that this type of truss should be toe-nailed on one end and attached with slotted clips on the other end. According to the article, this is to allow for movement of the truss. We require PE stamped spec sheets from the truss manufacturer to verify trusses meet wind and snow loads. These sheets give bracing requirements but never give recommended attachment requirements.