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Almost all of my roofs are tile or slate, we put ice and water shield on first, 30# over that. For composition, I think ice and water shield would be a waste of money.
Thanks.
I've asked a couple of other sources, and we have decided that if the underside of the sheathing is well ventilated that it won't hurt, except in the wallet.
Helen,
its a bad idea for a number of reasons, first and formost its a waste of money,any roofer who is worth his salt can provide you with a roof that does not leak, ice and water shield is only a recent invention they put a roof on my house 50 years ago that has never leaked just fine with out the stuff. Another reason is vapor you have to make sure the roof deck is well vented or you will just trap any mositure in the attic. Third unless you are putting on a lifetime roof what is the home owner going to do in 25 years when it comestime to strip it off and put on new shingles ? I gues you can apply another layer over the grace product but not for any of the sand/granule faced products. I try to provide my customers with some lasting value and I don't see how by charging them more now and creating a possible host of problems in the future I am doing that. I do however recomend one of the high tech roofing underlayments like rooftop guard inplace of felt. it provides far more protection then felt but at a fraction of the cost of covering the whole roof with ice and water shield
Lou
You know this water-vapor through plywood is an intersting theory, but I am not convinced it is true. If there is enough moisture escaping from the habitable space of a building into an unconditioned attic it will surely reach its dew point when it contacts any cool surface. If there is good attic venting, and good exhaust venting in kitchen and baths I don't really see it being a problem.
We have fully covered roofs with GAF storm gaurd when we knew permanant roofing wasn't going to happen for a few months, never had a problem. Now, that there are better felts, ie tri-flex 30 and the like, I doubt we would do it again. It does provided a confident dry-in material that won't blow off easily.
Interestingly, I have a sheep farmer down the road that builds foot baths for his flock out of ordinary CDX plywood, caulks the seams, it is completely water proof! Poor moisture management in building is not caused by roofing material.
Roof Top Guard is just as vapor impermeable as any other polyethylene based underlayment like Ice & Water Shield (and most other synthetic roofing underlayments like TriFlex 30, etc.) so vapor migration is not a relevant issue.
WR Grace put Bituthene on the market over 40 years ago for heavy duty foundation, plaza deck, and bridge waterproofing. It was a major breakthrough. A residential version, originally called Bituthene Ice & Water Shield, was introduced in 1978 (I have the first catalog and the samples are still in good shape) so it is not a particularily recent invention.
I agree that it is not necessary to fully cover the roof deck under asphalt shingles except in coastal or high wind areas, but it is a must under metal, slate and tile roofing IMHO.
I have covered several roofs in Grace usually at the request of the customer. Recently, I did an addition that was getting a metal roof so I did use Grace over the entire surface of that roof.
Alot of roofers up here use it on re-roofs because they can strip the roof and dry it in real tight before shingling.
You must use the high temperature version under metal roofs. Most folks don't even know that it exists. Bitumen bleed starts at about 180F on the regular stuff and 250F on the high temp, if memory serves me. They keep changing the product name, but it was called Vycor Ultra six years ago.
perhaps I should do some more explaining so I am not thought a complete idiot just somewhat of one, there are a lot of old roofs around here cedar shingles with a layer or two of comp on top with no venting. most of these roofs have enough holes in them its not an issue. on more then one occasion I have seen roofers strip the roof plywood over the skip sheathing cover the whole thing with ice and water shield right over the peak and say well there are enough air leaks in the gable end to take care of the venting. brand new roofs with no venting are a common sighting here. all I was trying to say is the tighter you make a home the more important venting becomes. what was not an issue can become an issue
housewright
lots of things are water proof that are not vapor proof, most house wraps, the goretex in my boots, roofing felt. and foot baths and roofs are a different situation, you want to put that 1/8" space at all your seams when you are sheathing a roof but not so much on a foot bath im pretty sure that an 1/8" gap is both water and vapor permiable, and no I am not say that replaces the need for good venting
Sweep8
we are ten years behind boston out here so that makes the year 1988 and even to this day I still know of one old school roofer who does not use it, and not all the lumber yards have the high tech stuff yet(triflex rooftop guard)
my great unlcle started installing slate roofs in the 40's has installed thousands of squares of slate in his life time, can count the number of rolls of ice and water shield he has used on them and the number of call backs he has had on one hand
this same uncle put on some comp roofs in the 50's got a call from the customer again in the 70's aplied another layer of comp shingles and to this day even though he has long ago retired he still gets calls from little old ladies who still live in these homes and guess who he tells them to call. I can't even begin to imagine the nightmare stripping a roof that was completly covered in "cheap insurance" would be. i would probably have to take it down to the rafters and redeck it
proper roof design good flashing technique and great venting thats cheap insurance
Something that's not been touched upon here is shallow pitched roofs---(4/12 down to 2/12). Most shingle mfgs. require a double layer of #15 felt paper. I have always gone the extra mile and installed Grace ice and water shield in place of this. NEVER HAD A PROBLEM... But I do agree that in most applications, covering the entire roof is a waste of money
You must use the high temperature version under metal roofs. Most folks don't even know that it exists. Bitumen bleed starts at about 180F on the regular stuff and 250F on the high temp, if memory serves me. They keep changing the product name, but it was called Vycor Ultra six years ago.
I spent a couple of days scraping "liquid" ice and water of a roof a couple of years ago. It was dripping off the drip edge like black icicles(sp?) and coming out the soffit vents. It was an unvented roof with asphalt shingles. The GRACE rep. was even suprised by it.
I spent a couple of days scraping "liquid" ice and water of a roof a couple of years ago. It was dripping off the drip edge like black icicles(sp?) and coming out the soffit vents. It was an unvented roof with asphalt shingles. The GRACE rep. was even suprised by it.
Yep. That's good ole bitumen bleed. Just what I was talking about. Sometimes the Grace reps don't even know they have a high temp product.
I still don't use the stuff much . . . just sparingly.
WR Grace warns, I believe even on the box, that Ice & Water Shield should not be used in hot applications like the desert Southwest US and under copper, Cor-Ten or zinc metal roofing in high altitudes. For high temperature conditions they make a 30 mil thick butyl & polyethylene self-adhering underlayment which they once called "Vycor Ultra", then just "Ultra" and have now decided to call it "Vycor Butyl". They had decided to use the tradename "Vycor" only for light duty wall flashings so this change makes no sense (not that any WR Grace change has ever made sense) unless they intend to sell it in strips for window flashing and compete with DuPont's StraightFlash, etc. I hope so since their rubberized asphalt membranes are not compatible with the plasticizers in thin flexible PVC, certain sealants, and EPDM.
WR Grace makes many waterproofing materials for residential projects
Self-adhering vapor impermeable roofing underlayments:
• 60 mil Basik - granular surfaced - temporary roofing?
• 40 mil Ice & Water Shield, Strips, and Detail Membrane
• 30 mil Vycor Butyl (aka Ultra) - high temperature application (up to 240°F)
• 25 mil Select - low budget application
Non-adhering vapor impermeable roofing underlayment:
Tri-Flex 30 - spunbonded polypropylene coated both sides with polypropylene
Self-adhering wall flashings
• 25 mil Vycor Plus
• 40 mil Vycor V40
• 40 mil Perm-A-Barrier - abrasion-resistant and masonry thru-wall application (green) heavier poly sheet
Fluid applied vapor permeable wall weather & air barrier:
• Perm-A-Barrier VP - sprayed or brushed acrylic membrane - on glass-faced wall board or CMU behind brick in a cavity wall application - also works well on plywood and OSB - tenatious adhesion even on damp substrates
- seals panel joints, window openings and nail penetrations - the ultimate wrb.
All WR Grace product names are subject to change without notice.
Thanks for the help. I just found out about the bituthene bleed today, so I'm printing out the whole thread and rereading it later. I had been specing Vycor for places getting ultraviolet, becuase I knew that the Ice and Water Shield doesn't hold up under daylight. My clients want the full coverege bituthene out of frustration, and I point to their neighbors houses and suggest that we start with good details for flashing and ventilation. Like taking the dryer vents all the way outside, and the bathroom vent coming on with the light, especially in houses with teenagers... and the AAMA has a good flashing detail for windows.
You just don't waterproof with silicone caulk, and a house that doesn't breathe properly is going to rot.
Of course, I also think 6 oz of dark chocolate per day is a good idea. :)
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