Gusseting Flat trusses with OSB

[Patman]

I'm a entry level BLDG Inspector in a small town, A local contractor has gusseted some flat trusses with 7/16" OSB that were damaged in a fire, basically he jacked them up to get rid of the 4 inches of negative camber and sandwiched them with OSB the entire length of the span, Is this too much rigidity that imposes on the deflection of the truss and has this caused a outward force on the exterior walls.
I have some experience in truss production but the fact they have been damaged in a fire and the structure is about 60 years old is a concern, the flat trusses were home made to begin with and he has removed most of the Webs and section of Bottom Chords because of fire damage, he claims that it is the same concept as TJI's only stronger, also take into account the bearing walls have sustained fire damage also and are presently being supported by some temporary framing and he plans on leaving the fire damaged wall in place and framing new walls up against it.
I would say this is cause for a call to an Engineer!
Any suggestions?

 

[DaveAtkins]

I would have a licensed, experienced structural engineer look at this building. I have at least two concerns. First, sheeting a truss with OSB does NOT necessarily make it like at TJI--the OSB in a TJI is continuous, and the OSB on the truss is discontinuous at each vertical joint (unless fastened to wood blocking both sides of the joint). Second, the new bearing wall can support vertical load, as long as it has a foundation wall or some other means of support beneath it (not a slab-on-grade), but can the existing, damaged wall resist wind and/or seismic loads? DaveAtkins

 

[RG88]

Agree with Dave 100% here.

In addition

This construction does not meet any building code that I know. There are too many factors here for you to go on visual 'inspection' and the contractor's experience alone. This should be cited as non-code-conforming construction and be referenced to the Alternate Methods provision in your respective code...the one that requires a design professional. This provision is usually in the administration chapter of the code book. If that doesn't work, check the new rafter span (since he removed some of the webs)....if they are 2x4s, they won't span far under ASCE-7 roof loads. OR since this contractor is so knowledgable, just have him provide you with the code section that covers this method of construction.

When I was an inspector, the rule was to cite non-code-conforming items and leave it up to the builder to hire the engineer if he didn't want to replace it or bring it up to code. If you tell him directly to hire the engineer, he may go to your boss and claim that you are intentionally causing him undue hardship (In as small town, this can get political...believe me I know).

Best of luck

 

[JAE]

Patman - if you are the "building official" per the governing code, you probably have the authority to order a load test on the trusses.

Review your applicable code to understand how this works. In the UBC or IBC, Chapter 17 governs in-situ load tests. (see 1713 in the IBC 2000)

So basically, you can request that the contractor hire a structural engineer to validate the new "design" through calculations and his certification ... OR ... you should request that the contractor perform a load test to verify that he indeed meets the load carrying capability that is required.

Anything else would be putting the public at risk.

 

[Patman]

One of those times when I wish I was the Building Official, I have another Thread posted on this same forum that should explain the situation as to why my hands are tied on this project and every other project going on in the town for that matter.