Roof structure

[Joseph Tribuzio]

I inspected a home built in 1973 - heres a picture of the roofing structure, i have not come across this type yet. ( I get lots of housing boom bungalows)

What type of roof structure construction is this?

Any Inherent concerns with this type specifically?

Any tips? resources?

[Michael Larson]

Built on site trusses.

I have no idea if they were done according to a plan.

Any sagging at the middle?

Here is a previous discussion.

[Joseph Tribuzio]

Thank you Mr Larson,

So its looks like a conventional field built (site built) truss - i have no verification of it being an engineer designed or approved construction. I will advise client not to attempt to modify it and that it is highly recommended to have an engineer evaluate it.
However, i will say here that there was a load of snow on it and it didn't seem to be sagging at all.

[Robert Ernst]

I agree with the others. Like mentioned look for sags in the rafters. There isn't much pitch to that roof so it would probably more likely visible with a lot of snow. Always check that those plywood gussets are attached well and none are missing.

[Kenton H. Shepard, CMI]

If that's 1/2" plywood and those rafters are more than 24" OC, the plywood is overspanned.

Leaks at the ridge, especially long-term leaks bad enough to soak the plywood gussets but not be visible from inside the home, can weaken gussets over time. Look for staining or decay indicating leakage.

[ROBERT V. YOUNG]

Gussets are sound building build practice for furniture building .
1: No ridge beam and span is 4-8 feet? . Still over sized
2: Look at nails. Some are starting to transfer rust staining on to sheathing, meaning
a>there is a humanity problem but not evident on all nails.
b>Shingles are nearing there life span and or lack of under-layment at one time or now.
3: over spanned.
4: question the gable venting louvers being over-sized. Might allow weather to enter on windy days.
Any decking that widely spanned would need to be 1 to 5/4 ply.

[Robert Ernst]

Without seeing the stamp on the plywood we can't say it's over spanned, but 3/8" plywood with H clips is common even on 24" in older homes.

[ROBERT V. YOUNG]

Those spans are over 24'. Clips are bylaw-ed now. 3/4 decking on thet roof would fail prematurely in my opinion.

[John Evans]

Robert,

How do you know the spans are exceeding 24"? With this truss design, it appears that the center vertical web support must be placed over a load bearing wall.

[Robert Ernst]

Well only Joseph can tell us the span or the thickness of the plywood. 3/4" plywood can span 48" with edge support and 36" without.

[ROBERT V. YOUNG]

Robert E.
look at the nail patterns for the shingles.In the roof decking.
4 nails horizontally equals 3 feet.
4 nails per single.

[Kenton H. Shepard, CMI]

Originally Posted by rernst1

Without seeing the stamp on the plywood we can't say it's over spanned, but 3/8" plywood with H clips is common even on 24" in older homes.

It was acceptable in many places for a while.

[agallatin]

Built in 1973 ! Nearly 40 yrs. , I would say they where well engineered , and proven ! Probably stronger than todays engineered !

[ROBERT V. YOUNG]

Yes Allin I agree . It was well engineered even if, or if not, by and architect.