What will show though asphalt shingles?
I’ve heard that small variations, such as those at the edges of the OSB deck, can show through to the layer of shingles after a short time. My question is – how much variation will show? 1/16″, 1/8″, 1/4″? Does it have more to do with the edges being regular long lines that the human eye easily picks up, or is there an actual big bulge or dip at the variations? Since I am using shiplap, do the back V shaped seems need to be filled?
Thanks for any info/experience you can pass on!
Rebuilding my home in Cypress, CA
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I'm confused. Are you siding with shingles? or is this a roof deck, with asphalt shingles applied over tongue and goove decking?
Jim
Never underestimate the value of a sharp pencil or good light.
Edited 6/1/2005 1:08 pm ET by JTC1
The roof deck of my garage was done with OSB, and on frosty mornings when the sunlight is at the right angle I can see the outlines of the individual sheets. I don't think there's that much variation in the OSB thickness (I can't see the outlines at any other times) so it's not like there are pronounced bulges or lines or anything.
I have seen some roofs where you could stand back and actually count the sheets of plywood. I suspect its the result of any number of things like cheap 3 tab shingles, no tarpaper, thin plywood or even 3 ply like you get at the big box.
The most common reason is 1/2" plywood on trusses spaced at 24" OC and of course no "H" clips
The main thing you can see is sagging between rafters.
The above are all pretty much true but partly miss answering your question.
The answer depnds a lot on the weight and thickness of your shingles. 235# Fibreglass 20 year three tabs are the thinnest of the lot and will telegraph a fart feather farther and faster than ATT can get the news out ahead of it.
240# asphalt 15 year three tabs are slightly stiffer and thicker, but stiull show an eight of an inch in variation.
The heavier architectural shingles will al hide the eighth inch and the heaviest do a fair job of hiding 3/16"
Another trick for hiding something like what you have is to lay with a 4" exposure instead of the traditional 5" or the metric 5-5/8". That way you have a triple ply insted of just two and headlap
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235# Fibreglass 20 year three tabs
Do they still even sell them in the great Northeast? We can't hardly get them anymore.Hey Mister Sushi, you forgot to cook my fish.
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Thanks for all those insights everyone!
"...will telegraph a fart feather farther and faster than ATT can get the news out ahead of it." OK, I'm going to have that one run throught the De"Dan Rather"nator machine to thranslate the folksy saying!
OK, so I am using 15/32 OSB (with H clips of course), on mostly 24" rafters, with Titanium UDL (like tarp thickness), plastic cap nails, and shiplap over the eaves. All will be covered by 3 tab shingles to match the rest of the house (which incidentally has 3 layers of roofing so it's not a good example). From what all of you have said, I'm apparently destined to create a Miniature Golf couse over my garage out of transmitted bumps, bulges, seams and edges.
OK, how about this. After the deck and shiplap are down (and inspected), I sheath over that with something thin, like 1/8" luan. This sheathing would be edged on the flat part of the OSB sheets to even out the edges, and cover over the gaps on the shiplap. It would also graduate the height difference between the shiplap and the OSB, which is about 1/8".Rebuilding my home in Cypress, CA
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Titanium roofing! What'll they think of next?So you don't know what a fart feather is?just a whisper of a whisker of the real bird.barely enopugh to disturb the air...so the analogy is that the lightest shingles show just a barely anything, even a slight wrinkle in 15# papregreencu, now that you mention it, it's been a few years since I've seen them...
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I'd rather be educated by broads. But you'll do in a pinch ;)
Hey, what do you think about using thin sheet stock to lessen the topography of the deck surface? I'd cover the entire surface, then likely coat it with copper napthalate to help protect it from long term damage. I'd use roofing nails and Polyurathane glue to hold it to the deck, then put the peel & stick (forgot to mention that earlier) and Titanium underlayment down. Then shingle away.
Thanks for the tip on the 4" exposure, unfortunatly I have another roof right next to it at 5", I'm not sure how that would look.Rebuilding my home in Cypress, CA
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Why not upgrade this roof to Architectural shingles now,knowing your 3 layer roof will need to be redone soon and you can make them the same at that point.
Trying to make the new roof match the old one if it's past it's prime may not be good since you may not get the same 3 tabs in a few years-archs may be all thats available.
All that said I think you're too worried about telegraphing on your upcoming roof.Use 30 lb. felt laid so you get double coverage and that will work fine.
I'm not going to upgrade now because of #1 Cost and #2 Future improvements. The house over the roof, and the roof over the second story need to be taken down to the rafters to have Radiant Barrier installed. Than won't happen for a few years, but it will happen. If I decide then to upgrade my shingles I can just nail over the garage roof ones.
The ones on the house are only about 10 years old, BTW.Rebuilding my home in Cypress, CA
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I'd forget the extra ply of underlayment. Too much labnor and cost fopr what you get out of it. And extra ply of 30# like slateman said will help fine. You ain't gonna make a 240# shingle look like it beloings on the Taj Mahal no matter hhow much effort and prep you do
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Thanks for the idea of using 30 felt as a "transition" fabric.
When I suggested the 1/8 luan, I was thinking it was like $5 a sheet - my bad. At $10 a sheet I might as well throw on another layer of plywood sheathing!Rebuilding my home in Cypress, CA
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I have been surprised to see the joints telegraphing through the new architectural shingles. There is a new commercial building here in town that showed the vertical joints really bad. I'm sure it surprised the builder too.
I think if you look at such situations closely you'll usually see that what has happened is that the sheathing has sagged.
What could keep the sheathing from sagging to an appreaciable degree? Would blocking the horizontal seems be enough, or are we talking needing blocking every 12"? Would an additional sheet overtop cure this?
(And I promise it wouldn't be more radient barier OSB pointed shiney side up ;)Rebuilding my home in Cypress, CA
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Sagging is a function of the thickness and composition of the sheathing, the rafter spacing, and the heat/humidity affecting the sheathing. Vanilla OSB can sag pretty badly, depending on the brand. Having an OSB-decked roof gets soaked before shingling is generally a bad thing.
Thanks for the tips guys!Rebuilding my home in Cypress, CA
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The quality of your OSB , and cover it with 30lb felt before it gets wet. When you see the 4x8 OSB thur the singles I guess the roof got wet. Been building for 25 years and always plan sheathing roof and felt the same day, or before rain. We have not have that problem. Are you trying to blend in your t&g overhangs with your main roof? If you did not plan that diferance in to your framing you may need to feather that out your main roof.