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-   -   leaking around ice+water shield? (http://www.diychatroom.com/f9/leaking-around-ice-water-shield-93654/)

longshanks 01-27-2011 11:56 AM

leaking around ice+water shield?
 
Hi all

Due to problems with roof leaks, shingle wear, and extensive ice damming, we had a contractor re-roof our house last year. The roof is 5/12 and we opted for 30 year certainteed landmarks. I replaced the old skylights with new velux units and had the valleys done with I+W shield. I also spent several hours/days in the attic, improving ventilation, insulation, sealing all leaks and perforations. There is considerably less heat loss into the attic now, but the new skylights still melt snow (as all skylights do).

We live in northern canada, December and January have had daytime temperatures between -10 and -20 celsius. This week it warmed up above freezing and as things melted we noticed a wet spot on the ceiling gyproc. I climbed into the attic and found an area of about 2' in diameter of wet roof sheathing. This spot is at the bottom of a valley, downslope from a skylight.

I called the roofer and he said he'd fix it but he hasn't showed up in the last 3 days. He has advised that they don't work in the rain. It has been raining steadily but tonight it is supposed to freeze up again.

I am thinking that an ice dam trapped water due to the rapid thaw, and the water backed up around the I+W. The roof design isn't that great, with the skylight melting snow and accumulating ice in the valleys below. Does that make sense?

The water damage inside is presently minimal. Any advice on how I should be approaching this? Can this sort of thing be properly repaired for the long term on a roof with 2' of snow at -10 degrees? Or should I keep the valley shoveled and have them come back in spring?

jmiller 01-28-2011 07:44 AM

You're right about the skylight melting snow, I've seen that before and always thought the velux design was weird that way.

Even if they put ice and water in the valley, if it's not wrapped down onto the fascia board at the bottom (which I almost never see anyone do, especially at the bottom corner of a valley) the water will back up from the gutter into the soffit and up under the shingles as well.

Was the leak near the eave, or say halfway between skylight and bottom of valley? It should be able to be fixed permanently with ice and water, but I'd make sure the skylight chase sidewall are insulated as well as possible (r 40, not r13/19, and that your ventilation system is actually working properly. I have a feeling you're losing more heat than what's coming out the skylight, and that if that were all that were coming out the ventilation should be strong enough to pull that air out of the attic and replace it with cool air from the soffit. The ice/water should be looked at as a fail safe IMO, not the first line of defense.

huntercrow 01-29-2011 01:03 PM

Hi I had the same problem for years and the only solution is to remove the shingles and completely cover the roof with ICE and Water shield and you will never have that problem again.I installed the fiberglass laminate shingle and have no problems . It is costly but cheaper in the end .JOHN

longshanks 01-31-2011 12:47 PM

to answer your questions:

the leak occurred about 2' in from the outside wall, or around 4-5' from the edge of the roof. Based on our roof configuration, I am guessing that there was an ice dam somewhere around the bottom of the valley.

In addition to sealing up all the ceiling perforations, and having about 18" + of insulation on the attic floor, last year I painstakingly fitted three layers of 2" blue styrofoam SM (R30) and tuck tape around the skylight tunnels. The amount of ice damming on the roof is reduced now, but still there. I watched the roof closely during early winter frosts, and wasn't able to detect any heat loss, except for a couple inches around the skylights.

Ventilation is a brand new continuous ridge vent, and it works. Attic is cool and well ventilated. There is limited ice damming except for a couple inches around the valleys. Looking around my neighbourhood at houses with similar roofs, it seems uncommon not to have ice build up at this time of year.

Now, in terms of what to do... The roof looks good as far as I can tell. They installed I+W under/around the skylights and fully covered the areas that have been problematic in the past, but I am thinking they didn't put a wide enough expanse of I+W in the valley that has now showed a leak. I haven't been able to track down the contractor to make a plan. Is this something that should be covered under my roofing warranty? I am thinking it may be best to shovel the valley now, and wait until a proper job can be done in the spring. Any opinions?

thanks for your input. I know this isn't a DIY question really, but based on the limited response from my roofer I am unclear what my options are.

huntercrow 01-31-2011 01:01 PM

Hi As you probably know ROOFERS are as dependble as the weather .They will do the minimun amount of work to get your money and then on to some other victim . The shingle manufactureres are not much better . You have to find the solution and tell them what to do and I found the only way to completely cure the problem is to put I &W shield over the whole roof as the leak in the valley may not be leaking at that point but rather up the roof farther and ending up in the valley so with the I&W shield over the whole roof there is no place the water can get in as when that membrane is laid it is there for ever because it is so sticky . My problem was like yours and I had this done a year ago November and last winter and this winter everything was perfect .ood luck with this JOHN

jmiller 01-31-2011 05:22 PM

I'm sorry that you had a bad experience with a roofer ^

It sounds like a typical ice dam at the bottom of a valley, and is at least partially due to an 'act of god'. At least that's what was claimed in the past, but now we see ice dams every year, and in my humble opinion it's as much due to the design of the house as anything.

IOW, it may very well not be the roofers fault, but I am pretty confident I could make it stop if you were my customer.

huntercrow 01-31-2011 06:47 PM

Hi My problem is fixed no thanks to the roofers I had before . i told the last roofer to cover the whole roof with I &W shield and that fixed the whole thing It was costly but worth it

Bob Mariani 02-04-2011 05:41 PM

I&W over the entire roof is a waste of money. You are using an expensive bandage due to incorrect building practices. An ice dam is created when the snow builds up enough (about 24") to insulate the bottom layers of the snow already on the roof. Air flow leaking from the house is the primary culprit here. This heat loss costs you a lot of money and is heating the roof sheathing to 35 degrees allowing the snow to melt since the snow above is insulated it and this roof is no longer cold. COLD is what a roof should be in the winter. Stop wasting heat to destroy your roof and air seal and insulate the attic. The other factor is a balanced ventilation of the roof sheathing. Allow 1" air space from a continuous soffit vent to the ridge vent. Use closed cell foam to get enough R-Value over the exterior wall so that thermal bridging does not heat the edge of the eaves. Some do not understand the physics here. The sun is not the culprit, its the heat you are pumping out of your house. Look at a house with ice dams, now why is the barn right next to it free of the ice? NO HEAT LOSS!


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