Ice shield on entire house?

I was just wanting to run something by you guys. I have a church that had some serious ice dam issues this year. This is just a simple roof 40 feet wide by 40 feet up on each side, it is about a 3 1/2 to 4 in 12, it is plywood decking. When I tore this roof off several years ago, I could look down in some of the roof vent holes and see another roof down below several feet. It appears when they did the addition many years ago they just planted new roof structure over old roof without removing.

This year they had ice leaks on this roof. I went over and the entire roof was ice, now granted we had 3-4" of freezing rain. But when the melting started, water backed up under black paper and leaked in. I had used ice shield along edges but it backed up even higher than that and went up to second seam in decking, about 8'. The church now had me price removing entire roof and felt, installing Grace Ice shield on entire roof, then installing new shingles.

My question is...Have any of you done this? What are pros and cons?

We don't get ice that often but this year was terrible. Now everyone is worried about ice dams so I need to find a reasonable way to install a roof that is 100% ice dam proof. Talk to me northern climate guys.

Thanks!

This was from a HD junk email I just got. Note that the entire roof they use for an example has I&W. http://homedepotforthepro.com/articles/article-roofing-with-cedar-shingles.php?cm_mmc=hd_email-_-032811_ProImp-_-0329_proimp-_-Roofer+Article+-PRO&et_rid=38105758

I run the lams @ 5" if necessary

Might have to go back to 'roofing' methods, as opposed to 'miracle cure' under lays. Before we had miracle cures, we shortened the courses. A 4" keyway gets less damage exposure than a 5" keyway. I did a few dimensional shingle 2/12's with Elks, at 4" exporuse, 6"+ Dutch-laps. Some are 10+ years old and often have 24"+ of snow.

Those reps can tell us that with the new underlay, there is no need to shorten exposure."The I&W will take care of it. Obviously, they fully expect lots of water under there.

In hurricane areas, we went to 4" or less exposure. The shingles didn't blow off though they had no seal strip. Take a folding rule and see how much deflection there is between 0" and 4", then, try 0" to 5". Try it at 3" for fun too.

Randy,, I did not explain well that the problem with that particular job was heat loss. So all of the I&W in the world would not have helped.

I agree w/ you tho ----- almost every job we do has 6' I&W.

Yeah Twill........after this winter I have come to the conclusion that 3' of I&W along the eaves is worthless. It really does zero good with ice dams since the first plywood seam is at 4'(and that is where the water enters)..........but I am glad you said it failed at even 9'. I have started telling my customers if they want I&W to go at least 2 rows high(6')........but after hearing you, maybe that won't work either.

Sorry sb..... 9' of I & W.

Twill59

Installed what 9'? I think that on airvents website it has a link to a great excel spreadsheet. Input what the attic space is and it will tell you exactly what ventilation systems to use. Yes, 36' of Ridgevent that has 18 NFA's is much better than 6 Box vents.

If you stick to the facts about ventilation and not opinions you will be much better off. Talk to the enginers that test this stuff. Talk to the Colleges that write articles about ventilation. I am sure that you will find the answer with the experts. Most of us on here are Roofing Experts yet still find the need to get knowlege from other Experts in our field. I have personally asked a few for opinions. That's the great thing about these forums. Can you post a few pics? That would help out tremendously.

Soldierboy

dougger-- I luv your adjusters up there. Send a few my way please. And U R so correct ( as is RG & TomB) about this product.....something for rookies and canvassers to sell to the homeowners is about it. Well actually it has already been "sold" to them thru so much mis-information. It is now a matter of verifying the idiots "knowledge" that they are about to hire. Little more than a Buzzword. Kind of like "lifetime" (wink wink)

I knew something wasn't right when I installed 9' of it and still got an Ice Dam call back in the 's. I think that is when my roofing education kicked into a higher gear

Not sure how to "Double" a properly vented roof AEI. A power vent every three ft? With fully open soffits, 10-12" rafters and 3.5" of insulation at the top wall plate? Powered intake vents? Help me out here....I'd like to see Dr. Frankenstein's creation

Thanks guys..

Soldierboy......there is nothing between the deck and the other roof structure below. When I look thru vent holes, I just see another shingled roof about 3 feet below. Big time fire hazard......

AEI.....In your opinion is 36 feet of ridge vent better than 6 box vents? Soffits are aluminum and have about every other one vented.

I have not heard back on this job......still pondering what to do. My supplier also stopped carrying Grace Select, they only have the heavy Grace.

If you install full ice shield manufacturers require "double the ventilation.

From what Air vent states on the snow zone. Snow is porous and is breathable. The right insulation and ventilation is key to preventing ice dams. However, a $65.00 roof rake and a maintenance fee to remove the snow 3-4' up every time it snows will work 100% of the time. I have seen ice and water shield on entire homes and seen the misery it has caused that homeowner. If you do this you would have to make sure; as stated above to vent, vent, vent some more our you'll be replacing the decking. What else is in between this deck and the roof below it? Where did they stick their furnace? I have a Dr. office that has their furnace in the attic on top of an old flat roof below a 15 year old pitched roof. They get horrible ice dams and he has us clear them 3-4 times a year. He is fully vented but with that furnace up there he creates his own problems. Just my two cents worth :lol:

Sooooo, does that mean if your not installing I&W to the ENTIE deck, there's no concern for adequate venting?....JK, a little ribbing there, for the MOTO stmnt....

Here's an interstng little tid-bit to ponder....There are particualr regions/areas up here that roofs hold FEET of snow throughout the winter & into spring....The ridge vent is useless at least half the year....

Whereas some building codes and local jurisdictions prohibit direct adhesion to the deck, most do not explicitly state their position in this regard. Individual manufacturers have allowed or limited such applications. Nevertheless, when installing self-adhesive membranes to the ENTIRE deck, it is necessary to allow for sufficient ventilation.

Personally, I feel it came about to mask inferior workmanship. -TomB Couldn`t agree more

100%I&W is standard procedure here in the Colorado mountains....It's not required by any local bldg. codes. Nor is it the correct way in a lot of cases....It's just the way they roll....If you don't; Eyebrows begin to rise....Personally, I feel it came about to mask inferior workmanship.

We run into "I told you so" situations all the time. The ice daming dynamics change significantly when you take a 25 yr. old shake roof with no I&W what-so-ever, or adequate attic venting & seal'er all up with I&W & comp, all kinds of crazy stuff starts happening....We're surrounded by idiots...However, "when in Rome".....