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We are experiencing problems with bouncy wood floor trusses. I'm wondering what the industry standard is on deflections (live and total load). Also, do you have any ideas on how to decrease the deflection without affecting the profit margin significantly?
Does SBCA have any guidelines regarding the size of a room in an attic truss? I have used a formula, length of room in inches divided by the depth of the bottom chord equaling less than 22. I was curious if any extensive studies or published articles giving more exact guidelines are available.
Is there a general rule of thumb to follow on chase placement within a top-chord bearing floor truss? In other words, how close to the bearing point of the truss can the chase occur?
How do trussed roofs perform in long-term service? Are there any reports of rusting in the nail plates, rot/insect attack, do-it-yourself modifications, or condensation and ventilation problems in the attic?
My framers are always complaining that the “trusses are bad.” I am looking for tolerance information that not only addresses the allowable variance in length and height, but also allowable variation in the top chord with regard to straightness (i.e. how straight should a pull string line from the top and bottom of top chord be?). Also, if trusses are set on a perfectly level wall, what variation is allowed from truss to truss (i.e. if I put a 10 ft. straight edge perpendicular to the trusses, how much can they vary in height, not just at peak or bottom but all along the top chord)?
What is the recommended way to frame gable end overhangs?
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.
I am looking for a company that can properly transport wood roof trusses on a one-time basis that are too large to fit into a box trailer. Trusses are to be fabricated in NC. Do you have any recommendations? Could be a specialty hauler or another truss fabricator in the area that has the special frame truss hauling trucks.
I stamp the bottom chord of my trusses with my company name and the name of my third-party inspector. Recently, my local building inspector requested another stamp with the on-center spacing, the total design load and the load duration factor. I have never heard of this before and I was wondering if you had any further information on this requirement.
I am researching building products for a new home and I wanted to use metal plate connected floor trusses. When I took my plans to the builder, they cautioned me against using these floor trusses. They stated that they were not engineered products, they do not carry any kind of warranty, and they do not know how long they last over time. My basement span is 30 ft., they said trusses could not span 30 ft. I really would like to use floor trusses, but now I am unsure. Could you offer any information?
We keep having problems with dry wall joints raising on the vaulted bottom chords in the track homes that we are building. The joints run from front to back of the house and the trusses bear on the side walls. The trusses are mostly 2-point bearing (a few in the front and back of the building are tri-bearing). The trusses span 40 ft. and have a 4/12 pitch with a tile roof. Is it common to have dry wall problems as the trusses deflect? How long should the roof be loaded before hanging sheetrock? Should the heel of the truss be allowed to slide out on the top plate?
Is lag bolting the bottom chord of a truss to the top plate of a wall a proper fix to correct truss arching, assuming the attic is properly vented?
I want to get a good definition on what causes “truss lift,” when the trusses will actually raise off the top plates of interior walls (even when nailed), causing the drywall to crack. Is it from drastically different temperatures in the attic and living area?
I installed roof trusses in my house and dry walled the ceiling to the bottom of the trusses. Now I seem to have a problem with the change of the seasons. Where the ceiling meets the interior wall, a gap opens and closes – in winter it opens, in summer it closes. What did I do wrong, how can I correct it and how should the drywall be installed in the first place?
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?
I am building a new shop that is 30 ft. x 32 ft. I need to free-span the 30 ft. dimension. Where can I get a load chart that recommends lumber size and strategic locations of the angle braces to support the free span? I am going to field erect the trusses and stick build them on the building.
I am planning a 36 ft. x 60 ft. clear-span horse barn with posts set 12 ft. O.C. If I use 2x6 verses 2x4 wood trusses what would the proper spacing be? The roofing is 29 ga. K-panels metal with insulation, and winter snowfall is minimal in our area.
Recently, I was invited to view a newly-constructed 60 ft. by 36 ft. barn, with homemade big timber trusses as follows: 36 ft. span, 12/9 pitch, construction was 26 ft. 2x12 rafters, bracing 2x6, ceiling joists were 36 ft. boxed, 6x12 out of overlapping (6 ft.), 2x12 glued and nailed center, 16 feet of joist doubled as an 8 ft. high loft, floor trusses were on 12 ft. centers atop posts deeply anchored with good footings, roof and wall cross ties were 2x6 on edge every 24 in., floor cross ties in the loft were 2x8 on edge every 16 in., 4 ft. snow load.
We are building a garage with a bedroom and bathroom and trying to find out what type of floor joists and roof trusses to use. The garage will be a 26 ft. by 32 ft. with a 26 ft. by 32 ft. room upstairs. But we don't want to have posts in the middle of the garage to help support the weight of the second floor.
I am currently working on a project where a wood truss system was loaded with a heavy spring snow. I do not believe the load was beyond the truss's design capacity, but how do you know? Is there safety built into wood trusses? If the trusses were loaded beyond their design capacity, it would not have been for a long duration.
The lumber used in most metal plate connected wood trusses is either visually- or mechanically-graded solid sawn dimensional lumber. However, the Truss Plate Institute's ANSI/TPI 1 allows the use of structural composite lumber (SCL) products such as laminated veneer lumber (LVL), laminated strand lumber (LSL) and parallel strand lumber (PSL). These engineered wood products can conceivably compete with sawn lumber and complement it in truss designs.
Girders are trusses specially designed to carry extra loads that are a result of the structural framing members they support. Sometimes a single ply girder truss is insufficient to carry the entire load, so the truss designer designs a multiple-ply girder. This is where identical trusses are built and fastened together to act as one unit to support the load. ANSI/TPI 1 states that girder trusses up to three plies thick can be fastened together with nails. Girders over three plies must be pre-drilled and bolted rather than nailed.
I am a building designer on a salt storage building project. I would like to use metal plate connected wood trusses in the design. What should I specify for the metal connector plates?
Has there been any research or studies on long-term deflection of metal plate connected wood trusses? How much deflection is allowed?
We have designed a custom home that needs a good solid floor, with low vibration perceptibility. The system we have specified consists of 2 in. of gypcrete over 1 and 1/8 in. thick plywood or OSB. The floor trusses are 20 in. deep at 16 in. O.C., spanning 31 ft. 6 in. The preliminary truss design shows a double top and bottom chord with a total load deflection of 1.30 in. (l/290) and a live load deflection of 0.65 in. (l/581). The basement ceiling will be 1/2 in. gypboard nailed to the bottom of the trusses.
Some building designers believe that gable end webs need to be L-braced to 90% of the web length, which sounds fine. However, they spec that scissors gable end webs need to be braced to 100% of the web length. That means that in the field they are notching the braces to fit around top and bottom chords – you can imagine how difficult that can be. Is that necessary or even the intent of the web L-bracing?
Is there a chart available on the allowable amount of deflection on floor trusses?
Are there charts illustrating allowable HVAC duct sizes that can fit between truss chords for various truss depths?
Do you have sound rating information for floor truss assemblies (i.e., STC and IIC ratings)? We are looking specifically for ratings for 12 in. floor trusses, with 1 and 1/2 in. concrete topping and without the topping. We are looking to meet the minimum code rating of STC 45 and IIC 45.