to tar paper roof or not

I am building a new home in eastern Canada and want to know weather to tar paper or not. The roof is sheathed with fairly fresh sawn boards ranging from 4" to 8" so I will expect some shrinkage and gaps. All the roofers I talked to say not to use the paper and just to put the shingles on the boards with ice and water shield up 3" from edge. Others such as real estate and home owners say to use it no matter what the roofer says. Still others say to use perforated tar paper. What should I do? Most of the roof is 6/12 and some is 14/12. What is the point of perforated tar paper, I can't imagine it stopping water of a shingle blows off. Thanks for any help.
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Everyone I have seen use paper. Check your shingle warranty it may be excluded without paper.
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habbi wrote:

I'd use a complete roofing system - secondary waterproofing ("Ice & Water Shield") along with a high quality non-organic underlayment such as ShingleMate from GAF.
http://www.gaf.com/Content/GAF/RES1/ROOF/RS_ShingleMate.html
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habbi wrote:

Check your local building codes and as also noted check the specifications for the shingles.
While I have never heard of that idea, the fact that it is boards rather then plywood there may be some reason for it. Also you are further north than I am and that may be part of the reason. Did you ask the roofers why they suggest this?
--
Joseph Meehan

26 + 6 = 1 It's Irish Math
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What kind of shingles, and what's the attic-space used for? Perforated tar paper has really tiny holes in it, and will therefor pass water vapor, but not bulk water.
Joseph Meehan wrote:

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Why not use it? The cost is minimal. It is standard practice. And I believe it is recommended if not actually required by the shingle manufacturer. You roofer sounds like he doesn't know his buisiness. Harry K
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habbi wrote:

What type of shingles? W/ open-decked roof, wood shingles were normally laid w/o tar paper so they dry out more quickly. But, the decking is roughly 80% coverage whereas sounds like yours is 100%?
But, the answer is to check w/ local code reqm'ts and the shingle manufacturer to ensure the installation is according to intended use and code.
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Duane Bozarth wrote:

You may have the answer.

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Joseph Meehan

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estate
6/12
What does the shingle manufacturer say on the package of shingles?
I bet for your type of roof they require 30# felt (not 15#). This is protection for the shingles like a pad is for carpet. Don't follow their directions and any warranty you might have is void.
Roofers hate the stuff because it is a PITA to install and makes the roof slippery to work on.
I have never heard of perforated tar paper but that would reinforce the carpet pad theory as being the only valid reason for felt.
Colbyt
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estate
6/12
I just re-roofed my home this summer. Tore off the old, that was also papered and I installed the new shingles over new (the heavy stuff at about $23.00us per roll) tar paper underlayment. Then layed the Owens Pro40 shingles. I did the same on my garage when I built it myself 5 years go. IMO, more protection and "cush" is better and ends with a smoother looking end result. The paper has lines on it and when layed properly removes the need to drop chalk lines for the shingles.
Use it, you won't be sorry.....
wz
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"habbi" wrote

estate
6/12
Something you need to address besides the felt is: You shouldn't have any "boards" which is sheathing, any wider than 6" when speaking of 1"x material. In the _old_ days they used just about anything they could lay hands on, 1"x material wider than 6" cups after time. I used to be a certified master installer by Certainteed, part of the training is to rip all boards wider than 6" in half. You must renail any existing sheathing you did this to. I'm sure anyone that has stripped/tore off roofing with 1" material will tell you stories about the cupping on wide sheathing material.
If you are using a composite material for roof covering, felt is strongly recommended besides the dry in process. If you are using a wood or cedar shake, installation is different than composite material. Code dictates ice/water shield, in my area ice/water shield must extend 2' into the living area. In other words, if you have a 2' overhang, a 3' wide ice/guard would only extend 1' into the living area which isn't enough. More ice/water shield is better than less, in the example I would double up my shield overlapping the first course by 6".
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this interesting note:

I've seen 1X6 material cup as well. So bad that sections had to be removed and replaced.
-- John Willis (Remove the Primes before e-mailing me)
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Uncle wrote:

...
...
Hmmm...just finished the new roof on the old barn which used 1x8 to 1x12 open-deck roofing and I would say it was flatter than many a new plywood-sheathed roof I've seen...been there since 1918, roughly.
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just did my sheds last sumer. boards up to 12" wide. Cupped, warped, cracked.
Harry K
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Harry K wrote:

Barn had/has lots of cracks, immaterial to function.
Just shows over generalization always leads to exceptions...will depend mostly on <what> was used and how it was applied, plus whether it has seen extensive wetting since...which was the point.
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"Duane Bozarth" wrote cracked.

Actually, you're wrong. The biggest factor is the unconditioned space over conditioned space.
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Uncle wrote:

On conventional roof, maybe. On wood-shingled open-decking, no. There's enough air movement there through the cracks and gaps in the shingles to let virtually any possible amount of moisture escape...w/o the tar paper, anyway.
House was built same way as the barn...just up there (the attic) over the last fall to clean up and install new insulation while repainting the exterior. All snug as a bug... :)
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30# Felt is required in Florida. It may have to do with wind driven water tho. That also gives you a second chance when a few shingles blow off.
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