Felt Over Grace I & W Barrier -- Overkill?

Chunkstyle

hey guys

i took the plunge today & bought a couple rolls of grace -- hoping to apply part of it tomorrow.

grumpy mentioned a guy who always goes over grace completely with roofing felt, as opposed to just lapping 4" at the top. is this overkill -- and maybe worse -- because you'd be stapling the felt down thru the grace, adding a ton of extra small holes? i know the grace is supposed to seal up really well around penetrations, but i'd imagine the fewer to begin with, the better. is the extra layer of underlayment worth the staple holes?

also -- is a run of aluminum flashing down the valleys (planning on closed, woven valleys, btw), over the grace, worth the bother, or is it stupid? i think i've only got 16" wide max. aluminum right now, so it's probably not worth bothering with.

thanks!

jproffer

All's fair in love and valleys , there is no such thing as overkill in a valley IMHO. If you have 16" AL, you might put the run down the center of the valley, then another with the edge at the center on each side...nail it down, ice and water, felt ran over from each side, as well as shingles ran over from each side (since you're weaving, there's no real thought to this one, it will just happen.

BTW, are you using archis or 3-tabs? If you're weaving 3 tabs you're OK. Not saying it's impossible to weave archis and make it lay right, but it's harder. If you're using archis, you might consider a cut (google: california cut) valley.

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Jim P.

AaronB.

I say do not cover the IWS with felt (certainly overlap it) and leave the aluminum out of the valley, proveided your installers are well-versed in the mechanics of waterflow within the valley assembly (dubbing the corners, proper nailing and shingle placement, etc).

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reveivl

I don't know this expression "dubbing", feel like explaining? Rich.

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minnesotaroofin

we call it a dog ear. cut the top corner of the shingles in the valley,

Grumpy

No reason for metal in the valley if you have ice shield.

bergenbldr

Only reason to use metal plus i/w in valley is if you are doing open valleys otherwise the overlap or weave will handle the water, i/w in a closed valley is only a backup.

jmorgan

We do not recommend felt over GIWS. Why have all of those extra nails? Exposure time is 30 days. This is a conservative number....most jobs can go longer exposed. Look for "edge curl" of the top plastic film, when it gets to 3/4", cover it up.
Jim

AaronB.

I think the only time I would like to see felt over IWS would be to act as a separator between the the IWS and metal roof panels so that the roof does not stick to the IWS as it expands and contracts.

__________________
http://www.roseroofing.net/
Seamless Industrial and Commercial Roofing Systems, Residential Repair. For Those That Demand Quality!
Free roof inspections within 12 miles of our locale.

Grumpy

Yes Aaron, or Rosin paper could be used in lieu of the felt, but either felt or rosin paper is a good idea over ice shield when installing a metal roof.