Frequently Asked Technical Questions
What is the life expectancy of wood that was used in an attic truss? Does fire retardant change the life expectancy?
I am developing a sustainable community in southeast Iowa. We have an abundance of cottonwoods nearby. I plan to have them sawn into dimensional lumber on the site and dry it there as well. I would like to use this material for trusses. A truss plate manufacturer informed me that because he had no data for cottonwood, he was unable to design trusses using it. Can you offer any advice?
I market 2x4 and 2x6 structural finger-jointed lumber. As of now, we have strictly sold it as a #2 product. However, we ran some through a bender at a sawmill to test the modulus of elasticity and it looks promising. The equipment showed no recognition of the joint; it acted like regular lumber. We would like to go forward with this venture in the hopes of offering an alternative MSR to solid lumber that may also be more cost effective. What do you need to have from us to get your approval?
I was working on a job that had trusses that span more than 78 ft. with a 9/12 pitch. We had the #5 truss being installed when the #4 truss gave way. The trusses that were being installed are a two part system. The bottom set is what you would call hip trusses. The trusses contained 2x6 bottom chords, 2x8 top chords and rafters, and 2x4 webs. The roof sheathing was to be 3/4 in. plywood, 15 lb. felt paper and roof shingles. The ceiling was to be 5/8 in. drywall. The #4 truss sheared about 1 in. off the wall. A knot was in that location on the bottom chord and both bottom chord and rafter were splintered apart into strands of wood. Also, the roof rafter on the bottom side (the edge that touches the top edge of the bottom chord) contains wane. Would this truss be considered ineffective? If not, why? How does one choose the size and location of these plates?
I am a structural engineer trying to locate average plate values such that I can recreate truss designs for a roof structure that is over two decades old. The plates are not marked with any type of identification, therefore I need to take a conservative approach in the design and determine worst case scenarios.
I am looking to purchase a new home and have one concern about truss construction. The prongs that come off the plates and penetrate the wood seem to only penetrate about 3/8 to 1/2 in. My question is: what keeps these plates from loosening over time and the truss from possibly falling apart from the load? Can the shaking from an earthquake cause the trusses to come apart?
I am investigating a roof failure in a 22-year-old structure. The connector plates have peeled open like a banana skin in several instances. The teeth do not appear sheared or torn at the wood surface. However, the plates will be in firm to one member and separated in the other (a gap of about 1/32 in.). Although there are large deformations, the roof is still standing. There was a heavy snow before the problem became apparent. Do you have any insights?
What tolerances are allowed for metal plate connectors in wood trusses? How do you take into account the possible presence of splits, waves and knots?
I am trying to determine the manufacturer of some wood trusses installed in the early 1980s in New Jersey. The stamp mark on the connector plates reads, to the best of my ability, TPL-153A (it could be PPL or TPI, but I am unsure). I need to get in contact with this truss manufacturer in order to determine design loads for the truss, as I am remodeling the store under the roof.
I am investigating an existing wood truss. The pressed plates used are stamped with “Combo Lock.” Do you happen to have any information on them? From what I have been able to determine, they have not been readily used in the last 10 to 15 years.