Ceiling cracks

[Jerry Simon]

My drywalled basement ceiling, approx. 27' x 13', applied to TJI ceiling trusses (upper and lower rails separated by OSB).  Two drywall seam cracks, four feet apart, running entire 27' length of room, cracks perpendicular to trusses.  Zero noticeable flex to floor, and minimal live loads above, and minimal dead loads, biggest being a refrigerator at middle third of span.

I could see having these cracks if they were running parallel to the trusses, where just a couple flexing trusses could cause cracks, but hard to envision cracks running entire 27' length of room when cracks are perpendicular to trusses.  In my mind, it would mean almost each and every truss would need to flex, more than a little, to cause such cracks.

Any thoughts at what else might cause these two, four-feet-apart, parallel seam cracks aside from truss flexing?  Could just one, or a couple/few, flexing trusses cause such cracking across entire 27' ceiling span?

[Tom Raymond]

It's not the framing that's moving. You most likely have mesh taped seams. They always crack.

 

[Jerry Simon]

1 hour ago, Tom Raymond said:

It's not the framing that's moving. You most likely have mesh taped seams. They always crack.

 

More than just cracks; big-a** splits I should have said.  And, this is just half of the basement ceiling; steel beam divides room in half, and cracks are only on the one, same-size half (room is about 27 x 27).

Would like to fault contractor, but seeing above, hard to make that case.  Pretty sure I'm missing something, though.

 

[hausdok]

If my memory is working properly, I seem to remember that these things are allowed to sag more than 2X. 

Many years ago I had an issue where I found that a local builder had been mixing truss joists with rim joists of regular lumber. The truss joists were custom made for that builder to the same nominal dimension of the joists so he wouldn't have to rip the rims to get them to the same initial height. The builder tried to sue me when I reported it in a number of houses he built The late JD Grewell had helped me with that case. According to the TJI manufacturer and what was called the Truss Council back then, even a 1/8 inch difference can result in damage to a home. I seem to remember J.D. had written extensively about it because he'd discovered homes where the trusses has begun splitting when placed under differential pressure. I'm not clearly picturing what you have there in my head, so maybe I'm full of s*** as regards this one.