I don’t understand where you make that interpretation. The language seems quite plain and straightforward to me. If they meant “directly over other types of shingles” I that is what they would have written. I see no reference to directly anywhere.
I would classify it as three layers and unacceptable. As a former firefighter it would make it very difficult to open that roof for venting.
On this, Tim?:shock:…LOL 
AHJ. :mrgreen:
heh…
You just need longer nails, right?
I was asked to look at a roof that was done 4 years ago. The HI had some concerns… 5 out of 6 vents installed upside down; one valley done with metal, the other 3 wove…with joints in the valley portion! The entire shinmgle job was installed on rotting plywood. No flashings anywhere where they’re needed.on the cosmetic side, 2 different colors used for the capping and some capping was comprised of the laminate.
The vendor paid some idiot 4 years ago to do this garbage work, now he’s gotta pay to have it done again, this time properly, if he wants the sale to go through.
Well are you joking or not? :shock: Good lord.
LOL
you would think they would peen over the standing seams…
Not sure if still true…
The building code does not address the number of layers of roofing.
If the engineered design of a roof
will accept multiple layers of roofing and sheathing…
It is OK to continue to build up…
We are working with a property now built between 1870 and 1880
where the original battens and shakes are visible within the attic.
Roof is now approximately
7 - 9 inches thick (with layers of metal, plywood and asphalt shingle subsequently added)
Architect / Engineer says OK…
sooo…
This was a materials question vs. simply layers. The code is specific as pertains to asphalt composition shingles over wood shake in this case. The code does, however defer to engineered designs and manufacturer installation instructions. I have not been presented with any evidence that this is an engineered design. Also, try to find a composition shingle manufacturer that says it’s OK to do it this way with their materials…
I will be there Friday as they are cutting the roof
to add ventilation (against mine and the roofer’s recommendations).
We will see how this turns out
…
The IRC does address the number of shingles.
And indirectly, it addresses the types of shingles. That is, if you live in a 90 mph zone (see Code maps), for example, the shingles you install should be approved by the manufacturer for that wind speed.
Good bump.
Its not so much the covering (shingles / shakes) being able to breath but rather that due to expansion and contraction of the shingles/shakes the new OSB sheathing would be an unstable substrate… not to mention other issues that may be at hand.
The code book does not address every issue therefore it often comes down to good / sound building principles…installing OSB or a substandard substrate is not sound building practices.
Jeff
I dont see anything in the IRC that would prohibit that, other than the additional weight which needs to be evaluated. Assuming the roof framing is adequate (some framing has reserve capacity), it’s possible they located and marked the rafters and used long nails to secure the OSB to the framing … not likely though … :shock:
Mr.O.Conner
Its not only the added load that has to be evaluated, ( engineer cost, and or, web truss, or even conventional rafter ).
Its the many possibility of nails lift on sheeting, the trapped air pace that can cause condensation between the layers, to acquitted flashing drip height for the perimeter of the decking.
The protrusions that exit and inter the decking,to a myriad of complexities that can shorten the longevity and the rafter or truss system period.
Does it happen.
My worst witnessed 5 roofs with the first being shake and then plies with 3 layers of shingles.
Not my job. I did no removal. Labors job.
The new decking and added expense were surmountable.$$$$$$$$$$$$$$$$
Just an opinion.
A valid concern if existing wood shakes are not installed over spaced plank decking/sheathing (which is how I usually see older wood roofing done).
You are dead to right on instailling ply over Shakes.
There are many ways to apply wooden shingles, shakes ETC. Once to apply another layer on Ply on top you are creating dead air spaces. Voids to capture and grrow condensation particulate.
Frost into ices in to liquid at the time of melting.
Look even if the first roofing system was applied correctly, how are you going to add plywood on top of the wood roofing system and maintain zero spacing is the point I am trying to drive home.
It is a bad practice to apply more than 2 roofing system atop 1 deck.
Plain and simple.
Why bother even installing the OSB deck? Today I arrived at my inspection to find an excessively wavy roof. The asphalt shingles were installed directly onto the wood shingles. The 30 year architectural shingles were ready to be torn off, the seller replaced the roof only 10 years ago…I was sorry to see another contractor taking advantage of an 85 year old (at the time) widow.
Joe. Is this a joke or a trick question? Seems lioke way too unbelieveable. Did you see such an installation somewhere or did you have a bad nightmare you are sharing with us in Fort Pierce, FL?