Preventing stuck shingles to Ice and Water shield- Felt over?
maine_tyler
| Posted in General Questions on
Is there a best practice for installing asphalt shingle roofs where Ice and Water shield is used?
I have heard the shingles can stick to the I&W (using Grace) making a mess at replacement– some folks seem to even think the decking will need to be replaced when the shingles are if I&W is used.
The roof structure and sheathing should last far longer than the service life of the shingles, so this seems crazy. Does anyone run felt over the I&W to provide a break, or am I crazy to be worrying about this? WOuld felt even help.
Maine.
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Replies
Tyler,
Once a good ice and water shield is adhered to the deck, there's no turning back. Wether or not you cover it with felt is somewhat inconsequential, as the next time you replace shingles it will be a mess either way. Tearing the shingles off, even if you could pay a crew to take their time (they won't, it's full force removal time when they break out the shingles forks) still leaves it pretty rough.
It is still worth having - 20 years of leak free service may mean just putting another layer over it, if the decking is still in fine shape. Worst case scenario is that 8 ft of plywood/osb gets replaced around the perimeter of a house, which is really a small material cost when it comes right down to it.
Thanks for the response Kyle.
I gotta say I find this kind of crazy. I see old board roof deck that's lasted 50, 100, 200 years... Now, every time someone says 'slap some Ice and Water on there', they're condemning the sheathing to replacement at reroof time?
Maybe I'm just out of the loop (not a roofer that's for sure!) but I feel like this should be discussed more at places like GBA and whatnot.
What about the people sticking this stuff to their entire roof? That's a lot of sheathing.
It certainly makes me not want to extend the I&W any more than needed (no more than a sheet of sheathing).
Tyler,
Why not set the I&W on your roof underlayment? When you re-shingle you'll want to replace both the I&W and the underlayment anyway, but you wouldn't risk damage to the sheathing.
Not that I believe in shingle warranties, but pretty much every doc Ive seen shows the ice and water applied directly to the decking. Do you think they would gripe about it if it were on top?
Kyle,
Yes, that's explicitly laid out in their installation instructions. It would definitely void the warranty.
Can you think of a reason not to do as Tyler suggested and run the roofing underlayment down over the I&W? That should allow the shingles to be replaced without damage to the sheathing.
I can't think of a good reason that it's not commonly done this way, for many climate zones.
I suppose an argument could be made that water could somehow get in between the sheathing and I&W, and then be trapped there with the only method of drying being diffusion, but that's a stretch, seeing as how shingles are already an impermeable layer with no drying potential.
Another argument may come from uplift / ripping all the shingles off in one plane. I think one of the major benefits to I&W is that it's permanent. If a high wind event were to get under a long stretch of I&W that's not adhered to the deck, it would be a nightmare for the roof, ripping off the bottom layer of shingles and potential allowing a whole lot of water into the structure.
The same number of wholes get poked through the deck in either case. I would think that by the time shingles need replacing, another layer of I&W could be applied directly over the first one, and all you'd have is a super thick I&W, with no downsides.
I have often wondered the same thing. One of my earlier questions on GBA was about that subject - are peel and sticks durable long term?
I waffle back and forth. Personally I think they're over rated for typical vented attic assemblies. Taped sheathing seams, ice and water on the eaves 3 ft past the wall line, starter shingles, #15 felt, arch shingles and appropriate nail patterns satisfy the fortified roof requirements, stop air leakage, and provide a continuous drainage plain.
There are cases where I think a peel and stick is appropriate, tongue and groove decking in a cathedral ceiling serving as the interior finished surface, with insulation on top. Board sheathing that has shrunk and has 1/4" gaps is another.
Perhaps it can also give a roof it's second life after the first replacement of shingles. If I lived where I have snow on the roof for months at a time, I could be convinced it's a good idea.
Is it better to have a product that performs better the whole time it is installed, or to have one that degrades slowly? There are a lot of angles on this type of question, and I'm certain there's no blanket advice that works everywhere.
It appears the Hammer and Hand folks do run felt over the I&W to the drip edge.
https://hammerandhand.com/best-practices/manual/6-roofs/6-1-kick-flashing/
Not sure of their reasoning, but at the least it provides a positive lap over the drip edge without adding another strip of adhered flashing tape, like shown in this ProTradeCraft video:
https://youtu.be/Qi5JiLrHGzI?t=64
As far as I&W over the underlayment; seems like it could work but I think at least a small part of the protection comes from being directly adhered to the decking (no space for moisture to creep into and live).
My plan for now is to basically follow the Hammer & Hand details, and let whoever does the reroof deal with any consequences, hopefully all minor.