For you engineering guys

Quick question on weight tolerance.

Great roofer, not so good with the mathematics of weight tolerance over a trussed roof. I know that no one will be able to give me an exact formula or solution, but I have the 21 squares stacked along the ridge (not over the ridge, but 3" down from the ridge) on one side in anticipation of laying it yesterday and today. However, because of the weather here in the Northeast, I will not be able to start this roof until Tuesday possibly.

I just need to know, should I go over and move some of the weight across the ridge to the other side. The last thing I want is for the weight to send the roof into the living room.

The slope is 4/12, 45’ ridge (and eaves obviously), 18ft along slopes (both sides).
The trusses are 2x4 make up, 24" centers, 5/8 plywood with H clips. If any thing else is needed to give me an idea, let me know.

Thanks for the information ahead of time. God Bless.

thats normal. no fear at all of material crashing through.(unless it"s a duplex or multi-unit)

we are talking around 7 bundle high stacks right? thats normal.
if you got 5/8ths over 24s, you are doing Good!

Yuk.,.,18’ 2"x4"-4/12 ?

5/8… youre prob good… personally, i dont recommend stacking it like that just cuz ive seen it cause sags, especially over 24’s but there could’ve been several other factors contributing to the sagging. one being it was over 7/16…

i can tell you one thing for sure, trust your instinct. if something is telling you to move it… move it. better safe than sorry. 2x4s bend alot easier than 2x6s. and if you didnt build the roof and cant vouch for its stability… i wouldnt take any chances. you dont always have to learn by mistake ya kno…

honestly i doubt very seriously it will fall thru if you terminated the plywood ends over your rafters but…well, after seeing an entire building collapse, i cross my t’s and dot my i’s on every project

go there. you will get your exact formula for weight load max’s and remember no matter what your “tolerance” number is… it doesnt apply to the entire length of the truss just the nodes.

The only thing that might happen is the plywood would sag between trusses, but at 5/8 I doubt even that would happen.

FYI: I load new construction roofs all the time and have NEVER had an issue with bundles falling through. And I load 10sq (2400lb = 1.2 tons) on 2 trusses. Mind you these are engineered trusses, when they are set, they rest 1/8" above the wall plates inside, and when I load the roof, they don’t budge.

On older homes where I can’t see the bearing walls, I stack them in 7-10 bundle stacks along the ridge. Never had an issue.

I’ve seen a duplex push the walls out and drop the complete roof from this. You have to remember that with 5/8" decking, there is already, just over 100#'s on the truss, plywood alone.
Next, go with your gut feeling. Probably wouldn’t take you 30 minutes to spread some out.