Interwoven Felt For Shakes?

ProSpec

What is the purpose of interweaving felt with wood shake shingles? Is it because the shakes themselves are not waterproof?

Thanks - jn

Bone Saw

felting every third course with split rolls ensures lapping felt without seeing black in between, keeping butt alignment 3 coarses apart is crucial too, hope that helps

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Ed the Roofer

The half roll gets applied for every course.

Typically, there is a 10" exposure for the shakes.

Felt is a guide line for setting the bottom butt ends and probably also a vabor barrier to prevent moisture wicking through the permeable cedar shake wood product through to the decking.

Installed properly, you are not supposed to see the felt between the joint, since it should be under the succeeding course.

Ed

Dang!!! It has been a long time since your last post.

Grumpy

30# shake liner felt is aprox 18" and gets lapped with every shake course. THis is a shake method of installation cedar perfection machined shingles are installed over a solid surface of felt, much like you would install your asphalt shingles.

Shakes are installed in a 10" exposure for 24" shakes and a 7" exposure for 18" shakes. I've not installed the 18", everyone gets the 10" due to labor pricing concerns. Smallr shakes = more labor.

It is my opinion that the felt is the actual water protection in the cedar roof system, much like a tile roof, the vapor barrier is the actual water protection, the tile just protects the barrier.

oldfrt

Do these shakes actually last with the felt paper under them.
I thought they had to breath to extend their life.
Last shake roof I did about 20 years ago called for 30#felt underneath.
They now look like they've been there 70yrs.

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neolitic

Real old-timer told me it was so that the shakes
could "move" as they swell and shrink.
Made sense to me, rough surfaces and all.
And that's why you don't need to weave the felt
with sawn shingles.

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Ed the Roofer

1st point to be made: The installation of the felt paper, in no critical way, determines the longetivity of the life cycle of the cedar shingle perfections or the sedar hand split shakes.

The reasons for cedar shake and cedar shingle roofs not lasting as long as one would expect are two-fold.

First, but not foremost, is that the quality of the hardwood sources have been extensively depleted, meaning softer and newer tree growth supplementing the demand.

Secondly, and in my own opinion, but backed up by resonable support, is the fact that many years ago, most cedar shingle roofs were installed on skip sheathing decking, which is a spaced board decking with a 1" x ~6" then an approximate 2" gap then the next board and so on and so on.

By having the skip sheathing, the cedar shingles were able to breathe and rapidly dry out the permeated moisture content from the exterior surface as well as the underside interior facing surface.

Most cedar shingle roof installations in current times, are installed directly on top of either solid plywood or osb deck sheathing. This does not allow for an air flowage under the cedar product. You will immediately begin to recognize the inferior products or the lack of proper under cedar ventilation within 1-5 years after first being installed. They will quickly begin to warp and split throughout the roof surface. If it were not for cedar actually being installed as a 3-ply for shingles and 2-ply for shakes methos, then leaks may be evident almost instantaneously.

There are several products on the market to re-create the under cedar breateability, with the most well known one being the Cedar Breather, manufactured by Benjamin Opydyke. Cost prohibition of the product and additional labor overshadows the benefit of doing the proper installation in most instances.

A properly vented installation of cedar shingles should provide at minimum, a 50 year projected life cycle.

An additional advantage of cedar shingles, is that unless completely degraded from rot, due to moisture inhibition, they are capable of receiving a reroof of standard composition or architectural laminated shingles directly on top of them due to their approximate 5" spacing per couse, which is ideal for a butt and run overlay.

Additionally, to add to what Grumpy commented on regarding the sizes and the spacing of the cedar handsplit shakes, cedar perfection shingles also come in a variety of sizes.

Although the most recognized size and spacing is to use the 16" nominal sized perfections, they can also be special ordered and purchased in larger sizes, which will allow for a wider spacing per course.

While the product price will reflect the additional size, the labor to install will go down approximately 18 %, which is significant in this most time consuming application.

There are also pressure treated and fire rated cedar shingle and shake products available, but the reasoning for using these variations is typically due to covenants or fire codes.

Ed

Grumpy

IN regards to Ed's point of ventilan research cedar breather by benjamin obdyke. I've won jobs on that fact alone.

Ed the Roofer

I'm presuming that you are agreeing with the absolute necessity of the Cedar Breather, if I am reading you correctly, right? (Or, skip sheathing.)

Ed

PlainPainter

I've used that Benjamin Obdyke behind cedar clapboard on sides of homes - man what really good stuff! Paint jobs last and last and last and last....

tnt specialty

The shake liner, (#30 felt), is a critcal component of a shake system, whereas with cedar shingles, is a stand alone system, (no felt is required and would actually undermine the shinlge's longivity).....

As tile should be; But in recent times, the underlayment has been heavily relied upon as a band-aide to improper tile system applications.

A couple of primary reasons shakes and shingle systems are failing as compared to shakes and shingle systems of yester-year are that the shakes have become thinner and shingles are being installed on solid sheathing as opposed to proper spaced sheeting.

A W Smith

Untreated Cedar shingles need to dry out evenly. If they are installed over solid sheathing or over felt they wont dry on the underside as fast as they dry on the face after a rainfall. This will cause cupping. Skip sheathing allows them to dry out from underneath. Treated shingles however do not absorb water and can be applied over solid sheathing.

Cedar Shake & Shingle Bureau Roofing Manual

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theroofinggod

Untreated Cedar shingles need to dry out evenly. If they are installed over solid sheathing or over felt they wont dry on the underside as fast as they dry on the face after a rainfall. This will cause cupping. Skip sheathing allows them to dry out from underneath. Treated shingles however do not absorb water and can be applied over solid sheathing.

Cedar Shake & Shingle Bureau Roofing Manual
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exactly felt between the layers is crap,even though it`s fairly common to find it done that way,it`s also the reason the shakes don`t last the 75-100 yrs they`re supposed to

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tnt specialty

That's right Al.

TRG? Hmmmm.....

Ed the Roofer

Applying felt between the layers of shakes is exactly what the Cedar Shake & Shingle Bureau show is the right way of doing it is. Are you referring to Cedar Shingle Perfections instead?

Ed

Grumpy

I am agreeing, that the under side of cedar needs to breathe and if spaced decking is no available then a cedar breather should be mandatory. Problem is when you are the only one bidding it, you are $100 a square higher than anyone else and it's hard to convince a customer it's that necessary, even though it is.

Ed the Roofer

You are absolutely correct about that point. I have run into the exact same thing where all of the other "Bidders", (Dang, I hate that term!), informed the home owner incorrectly, even though I had the Cedar Shake and Shingle Manual in front of their face.

Oh, they have been doing this for years, so they must know what they are doing!

Yeah, they have practiced doing it wrong for so long, they don't even know the difference.

Ed

Grumpy

Agreed. http://www.cedarbureau.org/installat...age4_popup.htm and http://www.cedarbureau.org/installat...al/page04.htm# for proof.

ProSpec

Hi Guys - thanks for all your replies. I'm now considering using RPM's syntetic shake (rpmroofing.net). Most of what I'm hearing here relates to real shakes needing to breath wich you don't need with synthetics. Can you guys think of any reason to interweave in that scenario? I was thinking of using Sharkskin's Ultra product and their Ultra SA Ice and Water at the eaves and valleys (sharkskin.us) My thought was to dry in the entire roof and then just install the synthetic shakes over the top of that?

Thanks again guys - Jim