# IWS under felt or over?



## BamBamm5144 (Oct 6, 2009)

Ice and Water on hips and ridges is just something they tell you to make more money off of it. Entirely not needed. If you still spend the money and do it, it goes under the felt of course.


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## caybound (Oct 7, 2009)

I hear ya, but even when we don't get hurricanes, we get tropical storms. We're one lot off the ocean and looking for any extra protection we can get. We've been maintaining private islands for 11 years and have seen A LOT of roof damage here in the islands- water damage too.


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## Clutchcargo (Mar 31, 2007)

You could put IWS over the entire roof. I would use a product that the shingles won't not stick to like Grace.


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## BamBamm5144 (Oct 6, 2009)

Yes, put I+W over the entire roof so that your roof deck cant "breathe". This way next time when you do your roof you will only have to remove entire roof deck.


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## Scuba_Dave (Jan 16, 2009)

Covering the deck with IW prevents water from getting to the deck
The soffit vents & rafter vents allow the roof to "breathe"

It also helps prevent against leaks in colder climates
There is a problem with some types of IW - the shingles do stick to the IW


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## Clutchcargo (Mar 31, 2007)

BamBamm5144 said:


> Yes, put I+W over the entire roof so that your roof deck cant "breathe". This way next time when you do your roof you will only have to remove entire roof deck.


I've heard that arguement before. Isn't the only reason you would want the roof deck to breath, to remove moisture? Using IWS over the entire surface would prevent moisture from ever getting that far. 
The shingles will not stick to Grace IWS product and Grace also said in thier FAQ that it's OK to cover the entire deck with IWS.


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## BamBamm5144 (Oct 6, 2009)

Shingles do stick to Grace. They stick quite well. We have just torn off a roof that was entirely Graced and that took an extra day. The top half of the plywood will be soft and spongy and need replacement. I have yet to find a roof that has been entirely I+W and have proper ventiliation and not need full replacement. Of course Grace Corp will say it is okay to use only their product. Thats the same principal as shingle manufacturers saying they are fine with their product being used as a second layer and the advantage of doing so is the first layer adds protection.

Also, the shingles keep moisture from getting to the roof deck, not I+W. If it was I+W that did this, roofs would not exist prior to 20 plus years ago.


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## Scuba_Dave (Jan 16, 2009)

I just took off the roof above my bay window
Not a huge area but covered w/Grace & shingles were not stuck to it
Wind can & does blow rain up & under the shingles
Shingles do not seal the roof deck from wind blown rain, IW shield does

My roof has proper ventilation & full IW shield
I guess I'll find out in another 20+ years about taking the shingles off
But so far with the Grace IW shield I have seen I'm happy
Roofing materials continue to improve
They didn't have asphalt shingles 100+ (?) years ago
I guess roofs didn't exist back then either


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## Clutchcargo (Mar 31, 2007)

I've taken shingles off of the Grace IWS as well and they didn't stick. The Owens Corning Product on the other hand is a completely different story, it's as if the singles and IWS are one. As far as the long term effects of a complete cover of IWS, I'll have to go by BamBamm's experience.


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## BamBamm5144 (Oct 6, 2009)

Ive torn off small areas where it did not stick either but a full 30 square roof that is 18 years old baking in the sun everyday changes the situation.

Scuba Dave - The guys who roof we replaced did the same thing because at the time it was the "best" way to do things. I have never had a problem with wind blowing rain up under the shingles. That is what the tar line is for. I+W shield is really only to help prevent ice dams and thats because of how it sticks to the roof deck. At least thats my experience with it. I personally think that if my G-Pa were still alive he would be wondering what the heck is with all these new gimmicks and nail guns and he would wonder what ever happened with roofs not leaking because the installers took the time to do it correctly.


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## Clutchcargo (Mar 31, 2007)

BamBamm5144 said:


> The top half of the plywood will be soft and spongy and need replacement. I have yet to find a roof that has been entirely I+W and have proper ventilation and not need full replacement.


When you say the top half, do you mean 1/2 of the thickness or the top half of the roof?
How do you think the moisture got to the sheathing if it was covered in IWS?


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## BamBamm5144 (Oct 6, 2009)

CLutch, I mean the top half of each sheet of plywood. From what I have learned it has nothing to do with moisture but rather with suffocation of the plywood if that makes sense. Plywood needs to be able to expand and contract otherwise it will delaminate or so Ive been told but could be wrong. If youve ever noticed a roof where you can see the plywood lines up to the ridge it is because the installer did not properly space the plywood to allow for this expansion.


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## meltdowndave (Apr 6, 2009)

Probably not much of a consideration in your case, but I thought that I'd chime in with s a counterpoint.

I opted to run 30 # felt beneath full roof coverage of ICW. Since the tile installation guide called for two layers of material, it was a matter of which to put down first.

With tile, the underlayment might be the primary underlayment should we have enough of them cracked. So, it was important to not have any unnecessary exposed nails going into the deck.

Having ICW atop the felt covers the cap nails and provides more "gasket" material for what penetrations that you do make. It also allows one to remove the underlayment with minimal effort later since it's not affixed directly to the deck. Given that I have mint condition 60 year old cedar tongue and groove planking, I didn't want a future roofing contractor to come along and try to convince us that it needed replacing because the ICW was too difficult to remove.

Although the battens are the primary means of holding both underlayments in place, there's also the usual number of cap nails tacking the felt down, too. So, even if we lost a few tile in a windstorm, I'll still have a roof.


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## caybound (Oct 7, 2009)

We've used dupont attic wrap/Ohagin vents/continuous soffit for roof deck ventilation. Only going to use Grace at hips & ridges, since post hurricane studies show that's where roof is vulnerable. My qustion is, do we felt right over the IWS or tuck the felt under it?


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## BamBamm5144 (Oct 6, 2009)

Having felt under the I+W eliminates the purpose of the I+W since it will not be able to seal directly to the deck. If anything, run the felt over it.


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## Clutchcargo (Mar 31, 2007)

BamBamm5144 said:


> Plywood needs to be able to expand and contract otherwise it will delaminate or so Ive been told but could be wrong. If youve ever noticed a roof where you can see the plywood lines up to the ridge it is because the installer did not properly space the plywood to allow for this expansion.


Let me see if I understand this correctly. You're saying that the IWS does not allow the plywood to expand and contract as it should so what's happening is the plywood is delaminating because it's decoupling through the layers. So moisture and ventilation has nothing to do with it; just expansion and contraction from the heat. Is that right? When you pulled off the IWS from the 30 sq of roof, it wasn't damp but still it delaminated, right?


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## caybound (Oct 7, 2009)

BamBamm5144 said:


> Having felt under the I+W eliminates the purpose of the I+W since it will not be able to seal directly to the deck. If anything, run the felt over it.


My question is, should I hold back the felt from the ridge/hips then overlap the felt with the IWS 6" or so. That way, there will be 12" of IWS on each side of the hip in direct contact with the ply, but the IWS overlap also seals the edge of the felt


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## jogr (Jul 24, 2007)

Caybound, 

I'm no expert but here are my thoughts.

You always want the upper material to lap over the lower material - otherwise any water on the upper material will drain under the lower material. 

That's easy when you are doing felt layers above the I&W at the eaves. When you are doing I&W on hips and ridges it doesn't make sense to me to have the I&W shed under the felt so I'd guess you apply the I&W to shed onto the felt. But I suggest you contact the manufacturer of the I&W to verify. 

Perhaps you could just felt over the I&W at hips and ridges as if it wasn't there at all - but this means that any water getting to the I&W will shed onto bare sheething rather than onto felt.


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## BereaRoofing (Nov 4, 2009)

*Ice guard on entire roof deck*

I have been tearing off roofs my entire life and you can install ice guard on the entire deck. This post was humorous to me because today I tore shingles off of ice guard. Grace is the worse brand to use if you install it on the entire deck; the shingles melt into it. In most cases with Grace, you end up replacing the sheeting, unless you want to chisel the shingles off for hours. I highly recommend Tamko ice guard. It is much easier to work with and it has a "gravely" surface that prevents the shingles from melting in. Also, the Tamko is much easier to stand on, especially when wet, in comparison to Grace. I believe it is also cheaper. In most cases, other than a hurricane zone, which is not my specialty, it is not necessary to install ice guard on ridges, it is a waste of money. However, I highly recommend running the ice across the deck and up any walls. This causes the need to remove siding which is the reason most contractors don't bother. If you have a "leaky" spot near step flashings, chimneys, etc. it is worth the time/labor to do this.


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## BamBamm5144 (Oct 6, 2009)

Run the I+W down the hip so that 18 inches is on both sides. You can then felt right over the top of it as if it wasnt even there. I believe you are over thinking it. The way you are suggesting will work just as well I am sure, I have just never done it that way.

Clutchcargo. The plywood delaminated off of the I+W. This house was not properly ventiliated. With a proper ventilated house I am sure I+W on the whole roof deck would work fine but whats the point in spending that money. I believe anything except two feet inside the "warm-wall" of the house is entirely useless for ice and water shield. The only reason manufacturers suggest it is because the make a lot more money on it. An average roll of felt costs less than half a roll of ice and water. ice and water is at most in rolls of 2 squares, typical felt is 4 square.

If you can do a job right with proper flashing and other techniques there is nothing to worry about. Go to roofing.com and ask the guys there if they think it is necessary to Ice and Water a whole roof.


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