Three broken truss webs

Here are some photos showing three damaged trusses I was hired to designed the repair. All three had damage to the same web, two were broke and one was cracked. Back in the old days all truss members were made from good quality lumber. Now it’s common to see lower quality lumber used on web members carrying smaller loads. In this case the broken webs were #3 grade 2x4 lumber. All three broke at a knot/defect in the wood.


I agree. I saw three damaged trusses on two pre drywall inspections this week. Craft are making field repairs and drawings are being made to reflect field repairs! Ass backwards!


How did they make field repairs without knowing the forces in the damaged member?


So, is this considered poor quality of lumber, poor craftsmanship or both?

Thanks again Randy for providing us with your insight. It helps in trying to determine if nonstandard repairs were attempted.


That’s the question I had for the job site superintendent. He said the repair was stronger than the engineered drawings and the engineer is going to create drawings to match the repair in the field. I should get a copy next week.

I’ve been down that road before, but it was the other way around. The project engineer told me how to repair it along with a drawing.


That’s the way it’s supposed to happen Marcel. Back then higher grade lumber was being used for trusses not all this stuff with knots in it. Number three lumber should never be used in a truss. Randy’s truss shows number three lumber.

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Thomas, that #3 2x4 was visually graded lumber. There is no way to know for sure how the knots impacts the tensile strength of the 2x4. I am sure the truss company factors in their cost to repair some damaged webs versus the amount of money they saved using cheaper lumber.


Thanks Martin!



The grading rules usually permit some percentage of visually graded lumber to be below grade – I believe it is 5%. ANSI/TPI 1 requires that all lumber used in trusses be of the grade specified by the truss design. A strict interpretation of ANSI/TPI 1 would require that the fabricator cull the 5% that is off grade. What are your thoughts on this?


The 5% tolerance is to account for variations in lumber grader judgement and for human error. It is not there to intentionally assign inaccurate grades to lumber. Truss manufacturers buy graded lumber – it is not a reasonable expectation to have them cull through lumber or essentially “re-grade” the lumber they buy. They rely on the grade to be accurate.

The fact that the lumber is marked with the grade stamp specified on the truss design is enough to meet the intent of provision 3.4.1 of the Truss Plate Institute’s ANSI/TPI 1(link is external): “Truss lumber shall be the size, species and grade specified on the truss design drawing.” However, any grade-allowed lumber defects such as wane or knots that occur in plated areas must fall within the quality tolerances for ineffective teeth outlined in section 3.7.4.


Modern day lumber quality is a great topic. I regularly tell buyers that lumber is the single part of their new house that is lower quality than is used to be. EVERY other part of a house is built better due to technological advancements, etc. But the actual lumber pretty much sucks compared to what it was a few generations ago (I put it a bit better than that when talking to the buyers).

My area of Oregon produces a lot of lumber and I’ve learned a bit about it over the years. Modern day, a lot of “regrowth” is produced. Meaning, a forest was cut down in the 70s, replanted, and then harvested again to build houses today. So, instead of old-growth with nice tight grain you get tons of knots and breaking points. I’ve had engineers tell me strength and capacity charts have been altered over the years to account for this. Honestly, with the twisted crap I see sitting at the stores I’m surprised there aren’t more problems with things like truss up-lift or just broken trusses like OP’s pictures show (yes, there may be more to OP’s situation but the point remains valid).

I definitely enjoy really looking at the lumber in older houses. The tight grain patterns and lack of knots or other imperfections are pretty amazing compared to what is used today.


Randy, It would be interesting to see your completed repairs. Great post btw.

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They have bred all the quality out of lumber to turn the crop over faster.

Randy, Very informative post. Thanks for including your fix recommendation and sharing.

Is this new construction in a cookie cutter development?
Just from a common sense, was a carpenter most of my life before I became an inspector, I see poor engineering on the vaulted truss plan. You can’t put that much tension stress on the King post/web of the truss and have a 2" knot in the member. It pulled the board apart when the roof got loaded.
If I was the inspector and this was a new home, I would recommend the homeowner demand that they remove the roof, redesign the trusses or walk away.
This is just the beginning of the problem.

House was built in 2005

Hello Randy,
Let me make sure I understand, are these after repairs were done? or these are the defect that needs to be addressed by engineer or repair crews? Thanks.

I did the inspection and designed the repair plans. The work hasn’t been done, but the homeowner will pay to have me verify the work was done properly when finished.

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One from today, 3 broken with field repairs. I referred them back to the seller for engineer documents or further evaluation by an engineer if no documentation provided. Does not look great to me :man_shrugging:

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LOL… do you live near Randy? Looks like the same house.

When any of you are looking at repairs that are engineered (speaking to the group because I know Brian knows this), repaired trusses or beams or whatever will have lots of nails/screws/etc. that are VERY specifically placed and spaced. This is one of the best ways to spot a professional/engineered fix. Joe Handyman is unlikely to know or care.

My old business partner was an engineer and used to talk about all the time. “Engineers don’t throw darts” is a phrase I’ve heard. As in, they don’t build things like I do when whacking something together some weekend. Attachment points are measured/spaced and done right. No bent over, shanked nails, no mixed fasteners. Things are done in a very deliberate manner. It’s actually super-easy to spot proper repairs but I agree we should also encourage buyers to follow up with plans/permits/engineering.