How many layers of roofing?

system · October 4, 2020, 5:17pm

Originally Posted By: dlabrake
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When inspecting a home with wood shingles and 2 layers of asphalt/composition shingles over that, is this a roof with 2 layers of roofing or 3. Some argue that in fact the wood shingles become the defacto sheathing component and there are only 2 layers of roofing material. As we all know, 3 layers of roofing is not allowed, so if we call it 3 layers, the roof has to be stripped, even though the current shingles may be brand new. Seems that both descriptions might work, but which one is accurate. Any roofers out there?

system · October 4, 2020, 5:17pm

Originally Posted By: jedwards
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Not a roofer, but I’m not buying the “wood becomes the de facto sheathing” bit. Three layers of any roofing material plus the “real” sheathing is an awful lot of weight for any typical residential rafter system, IMHO.

–
John Edwards

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system · October 4, 2020, 5:17pm

Originally Posted By: dkeough
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In Florida they allow 2 roofs. There is a section in the roofing code that will allow another roof as long as an engineer can state that the trusses are built to hold the weight that would come with 3 roofs.

In regards to the wood shingles, that is one roof along with the 2 shingle roofs make 3.

system · October 4, 2020, 5:17pm

Originally Posted By: dbush
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Dan, that is 3 layers of roofing. Anything above the sheathing counts as a layer.

–
Dave Bush

MAB Member

"LIFE'S TOUGH, WEAR A HELMET"

system · October 4, 2020, 5:17pm

Originally Posted By: gbeaumont
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hi to all,

I am with John & Dave on this one, normally the shakes are on a substrait and the shakes are therefore layer # 1, if a shigle is over that is has to be layer # 2, if a second shingle course is applied I would have to say that makes 3 and a tear of is in order.

regards

Gerry

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Gerry Beaumont
NACHI Education Committee
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system · October 4, 2020, 5:22pm

Originally Posted By: Blaine Wiley
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I called out a roof a while back with three layers of composition shingles. The seller was an absentee owner from New Jersey. He said they allow three up there. Naturally he was told to go pound sand.

Anybody up in that area that can verify that? Just curious. ![icon_biggrin.gif](upload://iKNGSw3qcRIEmXySa8gItY6Gczg.gif)

system · October 4, 2020, 5:17pm

Originally Posted By: dlabrake
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These are shingles not shakes. They are not on any substrate, but on 1x4 purlins.

system · October 4, 2020, 5:17pm

Originally Posted By: jonofrey
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Blaine,

Pound sand? I think I've done that!

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Inspection Nirvana!

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system · October 4, 2020, 5:18pm

Originally Posted By: jhagarty
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Dan:

That is 2 layers over the Original roof. Acceptable in this area.

--
Joseph Hagarty

HouseMaster / Main Line, PA
joseph.hagarty@housemaster.com
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system · October 4, 2020, 5:23pm

Originally Posted By: Blaine Wiley
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John,

I've been told to...many times. ![icon_lol.gif](upload://zEgbBCXRskkCTwEux7Bi20ZySza.gif)

system · October 4, 2020, 5:23pm

Originally Posted By: roconnor
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The IRC limits the number of layers of roofing to two layers (R907.3) and a maximum total weight (dead load) of 15 psf (R301.2.2.4). In high snow/wind load areas, I would list anything more than two layers as a “concern” …

–
Robert O’Connor, PE

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system · October 4, 2020, 5:18pm

Originally Posted By: Guest
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They’re wood shingles over purlins with two layers of composition on top.

Number one, that roof has got to be butt ugly. Number two, what the heck did they nail the composition shingles to. Nailing through a wood shingle won’t hold it all down. Nailing through the wood shingle then an inch of air into the sheathing is going to deflect the wood shingle, create tension on the nail and it’s all going to lift off anyway. It’s bad workmanship. Period

system · October 4, 2020, 5:18pm

Originally Posted By: dfrend
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I’d have to agree with Chad on this. And it must cause ripples when the water comes down the slope.

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Daniel R Frend

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system · October 4, 2020, 5:18pm

Originally Posted By: khamilton
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Also, I would think that all the nails from the two layers of comp shingles would have split the he$$ out of the wood shakes!

Kip

system · October 4, 2020, 5:18pm

Originally Posted By: jpeck
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Down here, as David said, it’s two INCLUDING the original roof. Unless an engineer wants to hang his hat on it, but I suspect that will be very unlikely.

–
Jerry Peck

South Florida