Product Performance

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?

Impact Sound Transmission Through Floor Assembly

Question: 

A condominium project I am involved with is experiencing a sound transfer problem through the floor/ceiling assembly between the first and second floor. You can hear every footstep, from an adult to a child. The floor assembly consists of a carpet and pad, 3/4 in. OSB sub-flooring, 15 in. deep wood trusses at 16 in. on center, 9 in. fiberglass batt insulation and a 5/8 in. gypsum board ceiling. The trusses span 20 ft. with air/heat ducts between the trusses. Will an additional layer of 5/8 in. gypsum board attached to 7/8 in.

Proper Bracing Of Valley Framing

Question: 

It is critical that permanent top chord bracing is supplied by proper nailing of the valley truss bottom chords to the carrying truss top chords, through purlins or properly installed rated roof sheathing. If the sheathing is not carried through under the valley framing, then the permanent top chord bracing must be supplied in another manner.

Fire Cuts

Question: 

What type of construction uses a fire cut truss? Could you describe a fire cut truss?

Truss Storage Responsibilities

Question: 

We have a customer that bought trusses in June. The trusses were shipped [ and one month later are] being set. The chords have weathered and bowed. What is the industry standard for dealing with this problem? What is our liability in this situation? We were not aware of any delays on the customer’s part and shipped as requested. Note: These trusses are 62 ft. scissor trusses.

Repairs To Field Modified Damaged Trusses

Question: 

As a home inspector, I have recently inspected an existing home with an attic truss system installed. Several of the truss web members have been cut away to allow access to an attic-mounted heating system. Can you recommend repairs to a truss with cut web members?

Truss Failure And Repair

Question: 

I am a professional engineer looking for information concerning the failure of metal plate connected wood trusses and methods of repair. I am looking for this information with regard to developing recommendations for the repair of truss systems in the floor structures of two-story multi-family dwellings. I see frequent failure of truss systems of this type in both in bending and due to catastrophic failure at the gussets.

Penetration Of Fire Walls

Question: 

Can a roof truss penetrate a one-hr. tenant separation wall without having a one-hr. rated ceiling? The building official insists that the 2x4 chords are combustible and nullify the integrity of the one-hr. rated partition that is constructed in an attic above an 8 in. C.M.U. bearing wall. The partition consists of gypsum board attached to 2 x 4 stud framing. The building official insists that a ledger must be attached through the gypsum board to support the trusses each side of the wall. This is almost saying that any rated assembly must have bearing only on other rated assemblies.

Deflection Of Long Span Scissors Trusses

Question: 

I was wondering if you have any information or anecdotes relating to the deflection performance of long span scissors trusses? We recently sold a job with 70 ft. long scissors trusses. The customer is in the process of installing the trusses and doesn't like the deflections he is seeing. To make matters worse, the scissors trusses are framing into a valley set (which we provided) that is erected on 35 ft. Howe trusses. The Howe trusses are exhibiting very little deflection. Any ideas?

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