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-   -   Using Felt with Cedar Shakes (http://www.diychatroom.com/f9/using-felt-cedar-shakes-18167/)

freddmc 03-08-2008 02:07 AM

Using Felt with Cedar Shakes
 
On another thread in the contractors forum there was a discussion about using felt with cedar shakes. Some felt it may not been necessary.

In my case I am re-roofing my roof with a 4/12 pitch. It has 20 year old 24 inch cedar shakes(split on one side and sawn on the other) The underlay is not solid sheeting but rather is spaced sheeting. On top of the sheeting is felt paper (with about 6 inch overlap).

I will be tearing off the old shakes and will be applying 18 inch hand split shakes(split on both sides). I realize I will have to put in some extra sheeting where the nailing for the shakes does not line up.

My question is about the use of felt. So the question is "is felt necessary at all?". Some say that the felt is REALLY for water protection, others say it is for wood movement and some even say don't use any felt at all so the shakes can breath and dry out properly.

And the last question is do the same rules apply to shakes that are split on one side and tapersawn on the other?

Thanks

Fred McNeill

Ed the Roofer 03-08-2008 02:45 AM

This guide from the Cedar Shake and Shingle Bureau should help you with your questions.

http://www.cedarbureau.org/installat...ual/page04.htm

Yes, for Cedar Handsplit Shakes, you absolutely do need to install interply 18" shake liner 30# felt between the courses.

Ed

skymaster 03-08-2008 10:58 AM

http://www.graceathome.com/pages/dow...s_Brochure.pdf
http://www.benjaminobdyke.com/html/products/cedar.html

Ed the Roofer 03-08-2008 03:19 PM

You will not be needing the Cedar Breather product under your new shake roof if you intend on leaving the spaced board skip sheathing with the gaps in between the boards.

I understood your pos to mean that you would only be filling in some gaps where the cedar nailing pattern will fall on.

Ed

skymaster 03-08-2008 04:06 PM

Oooooooops I is in trouble again!:yes: missed the "spaced sheathing" havent seen it in so many years brain automatically goes to plyywood of osb. I bad

freddmc 03-08-2008 05:05 PM

Ed said;
"You will not be needing the Cedar Breather product under your new shake roof if you intend on leaving the spaced board skip sheathing with the gaps in between the boards.

I understood your pos to mean that you would only be filling in some gaps where the cedar nailing pattern will fall on."

Ed, you are correct about "filling in the gaps" ONLY where the nailing pattern requires it.

So do I interprete your answer to say that " I don't need any felt at all-just nail on the shakes or are you saying a product such as Cedar Breather is NOT necessary but you do still NEED felt?

Thanks

Fred McNeill

skymaster 03-08-2008 08:22 PM

F E L T for sure. Read the cedar industry link FELT under shakes on skip sheathing

Ed the Roofer 03-09-2008 03:52 PM

Quote:

Originally Posted by freddmc (Post 105614)
Ed, you are correct about "filling in the gaps" ONLY where the nailing pattern requires it.

So do I interprete your answer to say that " I don't need any felt at all-just nail on the shakes or are you saying a product such as Cedar Breather is NOT necessary but you do still NEED felt?

Thanks

Fred McNeill


Yes, you absolutely need the "Shake Liner" felt.

No to the Cedar Breather, since the spaced board skip sheathing will provide the necessary underside ventilation to dry out the shakes after they get wet.

Cedar Breather is a product which provides a breating space underneath the entire roof system. Shakes need to breathe from air flow underneath them to not remain wet, which will deteriorate, crack and alow them to bow to easily.

Ed

Dale Chomechko 03-10-2008 07:21 PM

Felt & Cedar Breather
 
Quote:

Originally Posted by freddmc (Post 105434)
On another thread in the contractors forum there was a discussion about using felt with cedar shakes. Some felt it may not been necessary.

In my case I am re-roofing my roof with a 4/12 pitch. It has 20 year old 24 inch cedar shakes(split on one side and sawn on the other) The underlay is not solid sheeting but rather is spaced sheeting. On top of the sheeting is felt paper (with about 6 inch overlap).

I will be tearing off the old shakes and will be applying 18 inch hand split shakes(split on both sides). I realize I will have to put in some extra sheeting where the nailing for the shakes does not line up.

My question is about the use of felt. So the question is "is felt necessary at all?". Some say that the felt is REALLY for water protection, others say it is for wood movement and some even say don't use any felt at all so the shakes can breath and dry out properly.

And the last question is do the same rules apply to shakes that are split on one side and tapersawn on the other?

Thanks

Fred McNeill

Hi Fred
I have manufactured & installed shakes most of my life(36 years in the field)
Yes you can install shakes without felt as they used to for 500 years. The shakes have to be triple coursed, not double coursed like they do today(cedar shingles are triple coursed & do not require felt except for starter)
The problem tends to be cost of materials needed to acomplish this.
Cedar Breather as I see it is only effective under a triple coursed application on plywood, otherwise it really has no way to breathe. especially in 18" applications where it actually has 2 layers of felt on top. Good gimmic but hardly practical
Dale

tinner666 03-10-2008 08:22 PM

My concern would be the 4/12 pitch. Kinda low, IMHO.

johnk 03-12-2008 11:16 PM

Felt,felt,felt as Ed says.Shakes arent the same as they were 50 yrs ago for one and why not have the extra protection and its code where I come from:no:

Ed the Roofer 03-13-2008 12:44 PM

I would be extremely cautious, and make sure I use the felt shake liner, especially in view of the low pitch.

Shakes on a 4/12 pitch st as long as on a steeper pitch, especially if you are in a snow region, where it will soak up moisture and start to bow, and split. Cedar shingles, since they are applied in a 3-ply coursing, which is standard, will probably last longer, but thet too wil start to bow from retaining moisture prematurely.

Ed

Dale Chomechko 04-22-2008 01:10 AM

Bowed Shakes
 
Bowed shakes(especially 5/8 Tapersawn-18" or 24") are usually a result of something called cross grain. Picture a knot in a tree, the grain curls around this knot. the grain is crossing the side(not the face)of the shake.As this shake dries, on the face first, it starts to curl up & as time goes on it gets worse. Eventually snapping off. This is a #4 shake. This is not a #1, basically you have been ripped off because so few people know the grading rules. A split shake is not subject to curling because you are not sawing through this bad grain. Even a resawn shake is first naturally split & not subject to this.
The very best way to protect your roof from rotting even if it stays wet underneath is to get it pressure treated from the manufacturer. I have yet to see rot on these roofs & I've seen lots of 30 year old roofs & oh ya, I live in a rain forest

webbyonweb 04-26-2009 01:59 AM

Synthetic Underlay ?
 
I have manufactured & installed shakes most of my life(36 years in the field)


Hi Dale, I'm curious if you have an opinion on using synthetic underlays such as GAF Deck Armor instead of felt ? It's a superior breathing product, is much stronger, tear resistant etc, ease of install etc . . . your thoughts and experience would be appreciated . . thanks, Eric

Dale Chomechko 04-29-2009 09:52 AM

Deck armour
 
Hi Eric
Deck Armour does breath very well. I had an experience with it that totally amazed me. A mastic was used underneath it in this case & a piece of EPDM rubber overlapped it (dead valley /hip intersection-it was goofy)
the mastic fumes actually leached through the Deck Armour & buckled the EPDM proving to me its breathing capabilities.
Also I have seen Deck Armour protect a renovation for 3 months without leaking.I live in BC -150 inches of rain
Need I say more, it's a very good product.
You would still have to cut it into strips & layer it between each row of shakes.
If this is new construction or being inspected you may want to check with the inspector (try to get something in writing)
Dale Chomechko
DC Roofing Inc


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