Expert: Tom Souza - 11/2/2009

Question
Can I use 2 layers  of 15# felt for shake shingles instead of one layer of 30# felt both as a layer over the sheathing and also between each course of shakes? Please spell out the whole procedure for me.Thanks

Answer
Hi Grant

great Question

It is not recommended using #15 pound felt for a wood shake liner.
I recommended using a #30 felt 18" wide or 22" wide so the shakes will have only a 10" weather exposer

It is also not recommended to use felt a under the wood shakes unless you have solid sheathing, The reason is shakes need to breath from both sides top and bottom with solid sheathing it is recommended to use under the shakes it will work as a moister barrier to the solid sheathing and the wood shakes. Normally a shake roof has skip sheathing, This is a 1x4 or 1x6 spaced every 6 to 8" apart. this acts as the breather.

from my experience Applying a wood shake roof to solid sheathing takes away around 5-7 years of life.
a 3/4" thick heavy wood shake should last around 23-27 years using #30 felt and installed on skip sheathing this depends on weather conditions and how it's installed. this may vary.

Applied over solid sheathing will lower life, also depending on weather and install


I hope this helps

Good luck
Tom