Construction

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?

T-bracing

Question: 

The truss industry maintains that the design of truss roof and floor system permanent bracing is the responsibility of the building designer. System permanent bracing covers the entire structure and all bracing element interactions.

Duct And Light Penetrations Of Fire Rated Assemblies

Question: 

In a small scale multi-family residential project, I'd like to use a wood truss floor-ceiling assembly to achieve a one hour separation between units. I'd like to directly attach the drywall to the underside of the trusses & use the truss space for ducts & lighting (the floor above will be lightweight concrete on plywood sub-floor). UL assemblies do not seem to address the duct/light penetrations in such an assembly. Can I achieve a one-hour rating in such an assembly and how are penetrations addressed? Can the ducts in the truss space serve both units above and below?

Scissors Truss Diagonal Bracing

Question: 

We are finding it difficult to design permanent diagonal bracing for scissors trusses. The truss is often only a few feet in depth, which does not provide adequate room for diagonal bracing. Has SBCA come up with recommendations for permanent bracing of scissors trusses?

Charring Of Trusses

Question: 

Our home caught fire last month and burned partly through a tongue and groove ceiling to the trusses. Some are charred. Our contractor did a moisture meter test. An engineer for the insurance company said the trusses were only smoke damaged & the moisture meter test is invalid (it can be set to read anything). I found one article on charred trusses, but it’s pretty vague. We do not feel safe with the insurance engineer’s assessment because some of the trusses are obviously charred. We hired an engineer who agreed with us.

Retrofitted Shed Dormer

Question: 

I own and live in the middle unit of a one-story tri-plex that has a truss-framed roof. The interior has high ceilings that would potentially allow the addition of a second floor room. I am contemplating adding a shed dormer to create a second story bedroom. Do you have any suggestions as to how a shed dormer could be added? I am familiar with how to frame up a shed dormer if the original framing were rafters and a ridge board, but the truss construction has thrown me for a loop.

Alternate Nailing Patterns

Question: 

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?

Drag Loads

Question: 

Can you explain drag loads and how to calculate a drag load pertaining to roof trusses?

Determining The Load Capacity Of Trusses

Question: 

I am doing research for clients who have flat roof trusses to which they are adding a second story. We are now looking for information on the trusses to determine what their load capability is. What do you need to know to help us determine this?

Standard On Center Spacing

Question: 

What is the recommended standard spacing for open-web wood joists? I have seen them placed 24 in. O.C. Is this acceptable for a customer who will have an exercise room with 500 pounds of free weights? I understand there are problems with bouncy floors with 24 in. spacing. Is this true?