Are wood roof trusses with plywood gusset plates alright for house construction?

Monday, December 16, 2019

No, they are usually not acceptable, and the reason is that roof trusses for a home must be designed and certified to handle their anticpated live and dead loads by a professional engineer. Engineering drawings have to be submitted to the local building department as part of a building permit application. 

    We have seen trusses using plywood gusset plates, glued and nailed to the truss webs, that were constructed at the homesite by the carpenters, a few times in the 1980s in the Florida Keys. They appeared to be engineered, followed a standard web configuration, and the plates seemed adequate. But, more often, site-built trusses are like the ones shown in the photo above of a rural 1950s era home, with undersize gussets secured with only a few nails and definitely not following an engineer’s design for the web placement.

    There are engineer’s plans now available on the internet for building your own trusses with plywood plates, so it is possible. But factory-built trusses are so economical by comparison, when you factor in the labor cost, that do-it-yourself trusses only make sense if you consider your labor to be free. Plus, your homemade trusses are likely to get agonizing scrutiny for compliance with the plans by the local building inspector. 

    A home inspector for a homebuyer will always call out site-built trusses with plywood gusset plates for evaluation by a licensed structural engineer unless stamped engineering drawings are provided by the homeowner.

    Truss factories use spiked metal gusset plates, with their size, shape, and location specified as part of the engineering. The plates are sunk into the wood at connection points with heavy rollers or a hydraulic press to create an extremely stable connection.

    The only time we see plywood gusset plates nowadays is for a repair of a manufactured truss with metal gusset plates that was damaged during installation, like in the photo below. The repair gussets must be specified by an engineer and are always oversize to allow enough stiffness and nailing surface for the connection.

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  To learn more about roofs and attics, see these other blog posts:

Why is my roof sheathing sagging between the trusses?

Why is granule loss a problem for an asphalt shingle roof? 

What are the mistakes to avoid when doing attic improvements?

What causes roof shingles to curl up at corners?  

What causes shingles to buckle along a line on the roof? 

• Why is my roof leaking?

What causes leaks at a fake roof dormer? 

What causes a sagging roof ridge line?

What causes bubble-like blisters in a built-up and gravel roof?  

Why does it cost so much more to replace a steep roof than a low slope roof? 

What is "ponding" on a flat roof?

Is an attic required to have a light by the building code? 

How can I inspect my roof for hurricane damage?

Why is premature curl of roof shingles a problem?

How can I tell if a roof has more than one layer of shingles? 

What are the common problems with attic insulation? 

What is the life expectancy of an asbestos cement shingle roof? 

What's the average lifespan of a roof?

Why is it a mistake to replace a roof and not replace its flashings? 

Why is there no attic access hatch in the house?

What is the building code requirement for an attic access hatch, scuttle, or door? 

Does a roof with multiple layers of shingles last longer?

What can I do to prevent roof leaks?

Are roof trusses better than roof rafters (stick framing)? 

Why is a popped nail in a shingle roof a problem? How do I fix it?

What are the most common problems with wood roof trusses?

What causes a lump or dip in the roof? 

If my roof is not leaking, why does it need to be replaced?

How can I be sure my roofing contractor got a permit?

How many layers of roofing are allowed on a home? 

What are the dark lines running parallel to shingles on my roof?

Can metal roofing be used on a low slope/pitch roof? 

How can I make my roof last longer?  

What are the warning signs of a dangerous attic pull-down ladder?

How can I find out the age of a roof? 

Should I buy a house that needs a new roof?

Should I buy a house with an old roof? 

What are those metal boxes on the roof?

What does "lack of tab adhesion" in an asphalt shingle roof mean?

Why do roof edges start leaking?

Why do my dormer windows leak? 

Do home inspectors go on the roof? Do they get in the attic?

Should I put gutters on the house? 

How much of a roof truss can I cut out to make a storage platform in the attic? 

What's the difference between an "architectural" and a regular shingle roof? 

What does a home inspector look for when examining a roof? 

Do stains on the ceiling mean the roof is leaking?

How can I tell if the house needs a new roof?  

 Why does my homeowner's insurance want a roof inspection?

What are the hazards to avoid when going into an attic? 

     Visit our ROOF AND ATTIC page for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.



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