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.
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.
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?
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.
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
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.
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.....
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".
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.
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.
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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