Design

Responsibility Of Snow Drift Load Calculations

Question: 

Is the truss designer or the building designer responsible for calculating snow drift loads on a roof system?

Truss Attachment Information

Question: 

Would you please inform me of the specified requirements of the size and the amount of nail attachments from the truss to the top plate?

Temporary Bracing Documents

Question: 

Is it common practice for the supplier/distributor of a truss to provide a publication regarding temporary bracing with the delivery of the material?

Testing Wood Truss Strength

Question: 

We are building churches in Europe. These are modified pole barns and we are trying to use local materials and local volunteer labor. Since the truss is the heart of the building, I am looking for a method to test some completed trusses before the building is started to make sure they are strong enough.

Uplift Values On Truss Design Drawings

Question: 

I am a building inspector and I have a question on information provided on truss design drawings. What does the uplift reaction number represent? Some manufacturers are very specific and state “to provide for mechanical connection of the truss to the top plate with a connector capable of withstanding a specific load.” Others simply list the uplift reaction with no further information. These are the ones that have caused a debate as to what the number actually represents.

Notched Top Chords On Gable Ends

Question: 

The industry suggests notching the gable end truss to support the overhang. Is this wise? What about a structural gable, or a gable designed with drag loads, or one with only partial bearing? How safe is it for a framer working with a truss that has the top chord cut repeatedly?

Main Wind Force Resisting Systems Vs Components Cladding

Question: 

As an engineer, I have noticed truss designers in some high wind states routinely using “Main Wind-Force Resisting Systems” wind pressure coefficients as opposed to “Components and Cladding” coefficients to design for wind uplift. A roof truss is not a main wind-force resisting system and would have to have a tributary area of more than 1000 sq. ft. before qualifying for the lower Primary Frame coefficients. In my experience this practice is routine.

Safety Issues With Design Dead Loads

Question: 

Can I safely install 3/4 in. T&G, OSB on 2x4 trusses that are 24 in. O.C.? My roof was installed over 5/8 in. plywood without clips that have caused a lot of sagging and the shingles need replacing. I want to “fix” it one time and install architecture type shingles, but the garage is 24 ft. wide and 28 ft. long without any load bearing walls. My concern is the weight on the trusses. 5/8 in. plywood weighs 52 lbs. and the OSB weighs 78 lbs. for each 4 ft. x 8 ft. sheet. The roof will require about 84 4 ft. x 8 ft. sheets to cover, which equals about 2,184 lbs.

Blocking For Lateral Displacement And Rotation

Question: 

I am a building inspector and have some questions regarding how to apply IBC 2012 2308.8.5 (IRC 2012 R802.8) (similar IBC 2015 2308.4.6 & IRC 2015 R802.8) to trusses, especially those with high heels:

Designing Trusses

Question: 

I'm looking for a book that will provide formulas and design criteria for trusses. Can you give me any suggestions of where to find a book or fairly inexpensive software?