Looking to put 3/4″ Tapersawn cedar shakes on new construction. One guy recommends a two-ply installation with felt paper between each course, on solid sheathing. Another guy recommends a three-ply installation w/o felt paper between each course, on spaced sheathing. Anybody got any opinions?
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Replies
felt between each course on either spaced sheathing or "Cedar Breather"
Do not install on solid sheathing. Also discuss fasteners , ridge cap, & flashings.
Mike Smith
Rhode Island : Design / Build / Repair / Restore
i prefer to ice&water the entire roof,apply cedar breather and hand nail, this way your attention to seams and workmanship are constant. i also like using cobra vent with solid cedar boards for capping.
Dear MB,
I've done it both those ways and some others. I don't see any harm with weaving felt b/t the courses, but it is a lot of fuss. Doesn't seem necessary.
In modern roofing, the underlayment makes the roof. And particularly with shakes, few people will pretend that they can keep the roof dry. So my best is to half lap two layers of felt. I use Roofer's Select or ShingleMate. Both are vasty superior to lumber yard 15# or 30# felt.
You will hear a lot of yak about venting under cedar. I've found that it does not preserve the shakes. They are very quick to dry and fairly self ventilating anyway. A strip of zinc or copper at the ridge, I like a copper cap, will do far more to extend the life of the roof.
On the other hand, I see a lot of new cedar roofs that have to be torn off when a ventilation layer under the roofing causes misalignment of the flashing and underlayment. The only fix is starting over, so don't fall for that.
Regards, Fred
[email protected]
MB - Yes, you'll hear lots of yak - that's why you should always go to an authority on the subject. Click on the link for a good technical presentation. You'll note that the answer to your question also depends on your locale and climate. Definitely use cedar breather under the shakes and keep people off the roof after it has been completed.
T. Jeffery Clarke
Edited 4/8/2002 12:06:00 PM ET by Jeff Clarke
Tapersawns are sort of a hybrid between shingles (ie Royals or Perfections) and hand splits. Marty at the CSSB says that he likes to put them down over solid sheathing with felt every course, like a hand split. With a solid sheathing and felt on every course, there is just no way these things are going to get ventilation on the underside. Heck, even if you go with spaced sheathing, with felt on everycourse, it still isn't going to ventilate that well. I was thinking that as a "belts and suspenders" solution, I could go with three courses rather than two (using a 24" tapersawn at 7 1/2" exposure) with NO felt in between, on spaced sheathing so that they can ventilate from below. This is more like a conventional shingle installation. As an additional safeguard, I will CCA treat them. Comments?
One of my clients has at least 150 sq. of 24" tapersplits with 7 1/2" exposure. Over solid sheathing, cedar breather, ice & water full height, lead-coated copper flashing. No leaks, no problems, completed in 1995. BTW - also with LCC-lined yankee gutters (again, no leaks, no problems). We consulted with Homer Earll of the CSSB who knows more about cedar shakes than anyone I've ever met.
T. Jeffery Clarke
Quidvis Recte Factum Quamvis Humile Praeclarum
Edited 4/8/2002 1:31:57 PM ET by Jeff Clarke
Dear Jeff,
We all have our experiences. Winter before last, I saw $240,000 worth of brand new cedar roofing on 8 roofs fail directly b/c of cedar breather. Not a single shake would need to be removed if they had left that product off.
Wood roofing won't last a single year longer from venting. There has never been a controlled study to show that, and I've never seen it when I pull off the old ones. Where there is some poison, the cedar is perfect 20, 25 years with no venting. On dozens of roofs.
Regards, Fred
[email protected]
Fred - You seem to feel that I disagree with copper/zinc ion ridge roll/strip - I couldn't agree more - it really works on a variety of roofing materials.T. Jeffery Clarke
Quidvis Recte Factum Quamvis Humile Praeclarum
Dear Jeff,
I'm not confused about that. Nor am I ever going to wonder about whether we all want water tight, long lasting roofs.
My position is that venting doesn't get us to either of those places.
Regards, Fred
[email protected]
My position is that venting doesn't get us to either of those places.
If you stop venting, Fred, I'm sure we can all get there together <G> BFN ...
T. Jeffery Clarke
Quidvis Recte Factum Quamvis Humile Praeclarum
Edited 4/8/2002 1:49:41 PM ET by Jeff Clarke
Dear Jeff,
Most people would be much happier if I did.
Granting your wish, Fred
[email protected]
fred : yur so hung up about not venting attics that u let it slide over to not venting cedar roofs..
we always use either zinc or copper.. and neither one will do a damn thing for the roof if the roof remains wet for long periods after rain..
solid sheathing will not allow the back of the shingle to dry quick enough .. so either skip sheathing or cedar breather will remain our spec.. if you encountered roofs failing because of cedar breather.. you're not telling the whole story.. the whole story will no doubt include a lot of bad detail and bad installation..
cedar breather will only enhance the lifespan of the cedar roof if it is installed correctly and detailed correctly..
solid sheathing will never increase the drying rate in our climate (33" year plus lots of fog).. and the result will be premature failure in the range of 10 to 15 years...my source is NOT the cedar bureau.. nor anyone who works there...
so.. your personal observation is different from my personal observation... guess which one i'm sticking with... yur buddy... MikeMike Smith
Rhode Island : Design / Build / Repair / Restore
I've just got to step in here and poke a few holes in fred's story to let it ventilate.
I disagree with just about everything he has said here about shakes and am still laughing about his contention that cedar breather caused shakes to fail. He may occasionaly have a case when it comes to unvented attics but he is going so far over the edge on this roofing that he might fall off.
The reason he has seen so many shake roofs fail is because he fails to interweave the felt to keep water out in the first place. He leaves the felt out and plentyu of water runs under the shakes without being re-directed to the surface of the next course down. Sop they soak up more of the water in the first place and then because it is unvented they hold it longer and rot.
I've done tear-off for re-roof on hundreds of shake roofs, in hot, dry Texas Plains and in cold, wet Colorado Mountains. I spent twenty years doing it before moving to colder, wetter New England. Without exception, the roofs that have lasted longest were installed with ventilation and with felt interwoven.
Period.
fred, you could restore your credibility by stepping down from the experts podium, and editing your posts to say, "In my humble OPINION"
to the original poster - In my experience, the exposure to the weather is more a function of the slope pitch and design style than of anything else. You should always uyse the felt interweave. It really is not harder to do when you know the tricks of the trade. Generally speaking, the roofer who wants to avoid using it doewsn't have as much experience and doesn't know as much as he should. that is an indication to me of which guy you should go with, all other factors being equal. And installation technique effects the life of a shake roof more than almost any other type of roofing material, so choose a guy with demonstrable experience.
Excellence is its own reward!
Dear Piffin,
I speak from Vermont experience. That's all. If you 've good luck roofing in a desert, consider it good luck. We have too much wind, rain, and snow to depend on myths.
Go find any scientific study to validate your claims about cedar venting. Search the Internet all day long. It's not there. Don't you think the Cedar Breather guys would be waving these studies around if they could? But they can't b/c it doesn't work. And it makes detailing around valleys, curbs, eaves, and ridge far less reliable with blown snow. I see it and I fix it.
But if you are looking for a fight, you won't find it here. Go pester the women about their vibrators and they'll kick your ### around the block again if that's what you are looking for.
Without regard, Fred
[email protected]
I don't know why everyone's gripin' so much. Seams like the same old Breaktime to me.
Edited 4/9/2002 12:03:52 AM ET by jim blodgett
jimbo.. when all around you are losing their heads.. and you remain cool , calm & collected.. it usually means you don't know what the f**k is going onMike Smith
Rhode Island : Design / Build / Repair / Restore
Fred hows it going? Not a bad winter up there this year eh? I am in PA. Not as bad but not much better here. I don't think many products on the market can do what they say for sure. I think time will tell. What I like to do is make my decision based upon logic. I would think that improved air flow would create a quicker dry time for the shakes. I think as roofers we can get the flashing thing figured out. I have never had a problem as you have had with the flashings but my advice would be to use larger steps along walls and back bend a kick toward the center of your valley flashings. Good Luck.
regardless fred,
You go ahead and paper your roofs in with studies (which you haven't done so well in posting your own self) and I'll stick to the basics that have served roofers well for centuries. The only place I have seen shakes applied like you recommend as a standard installation was in West Texas. When I asked why they took that shjortcut and wouldn't it be better to do it right, the answer (This was from the owner of that branch of the largest roofing company in the state) was that even though woven felt would make it last longer, normally, they assumed an average ruination from hailstones at about every six to nine years so there was no reason to provide a forty year job.
on your sidebar...
If you were paying attention to what I posted to the "ladies" it was about their lack of attention to the words written by another. There was an assumption made based not on what had been written. I pointed out the error. And I can't remember that they ever licked my ###.
Excellence is its own reward!
OK, studies smudies. Here's what I've witnessed: I installed a cedar shingle roof (18" perfections) 15 years ago on 1x3 furring over felted plywood. I installed the furring in 3 and 4 foot sections randomly spaced with an inch or so between each piece on the butt ends. I used a 5" reveal. A year or so later a neighbor of this customer had a new cedar shingle roof applied directly over felted plywood. I was called back this past summer to roof an addition on the first house. The cedar shingles are still in relatively good condition. The neighboring house now has asphalt shingles on it (cedar was replaced over a year ago).
Now, here's what I don't know: 1)What grade the shingles were on the 2nd house. They appeared to be perfections, but I don't know for sure. 2)Did the house change hands and the new owner didn't like the look of cedar? I doubt it, but I've seen stranger things. 3)Was the roof installed properly? Appeared to be. The flashing details were good, which is usually a good sign.
About 6 years ago, I replaced a 6 year old shake roof applied over felted plywood. I used the same furring method (7 1/2" reveal with 24" resawn shakes). I haven't seen the house recently ( it is not easily accessable ), but have heard it is doing well.
I use ice barrier membrane in the valleys and eaves under the furring. I use 18" felt with shakes, but not with shingles. I flash with 16 oz. copper or lead coated copper. I have not used cedar breather. Might be a good product.
Copper ridge roll helps keep the moss off. A strip run every four feet or so works better. Keeping the trees cut from over the house works the best.
These practices seem to work in my location (central KY). Different climates may call for different measures.
Edited 4/10/2002 7:26:58 AM ET by grantlogan
It seems logical to me that shakes or shingles could last longer if ventilated from below, which makes me inclined to install them on spaced sheathing. However I'm still confused. How do they vent from below if felt is placed between every course?
I also wonder how you all feel about CCA treated Royals, installed 3-ply on spaced sheathing without interwoven felt? This method is specified by the Cedar Shake and Shingle Bureau. My project is new construction near Philadelphia, PA. Roof pitch is 10/12. We want to do it right so that it lasts. Snow is not much a problem here, but humidity is.
Our original idea was to install CCA treated Tapersawns. It is my understanding that Tapersawns (altho called shakes) are very similar to Royals (shingles) only thicker (5/8" to 3/4" butts) and a little less uniform. One CSSB representative has advised that Tapersawns can be installed like shingles- 3 ply on spaced sheathing without felt. One roofer has suggested that a 3 ply installation without felt allows water to penetrate deeply into the shakes- so they get thoroughly soaked through a few layers and stay wet for a long time. This roofer has argued that it is better to use felt interwoven so water doesn't penetrate so deeply.
Any thoughts? I also would like to know your general thoughts about Tapersawns versus Royals and your experience with CCA treated shakes and shingles. Thanks for your advice.
mom.. use the felt on every course... y do u keep asking this question.. it's been answered.. now u have to decide who's advice u agree with...
here it is again.. skipped sheathing, (or cedar breather ).. felt every course..
SS or HD Galv. fasteners.. pay attention to flashing.. use a copper strip at the ridge to aid in the prevention of algae & moss...Mike Smith
Rhode Island : Design / Build / Repair / Restore
In our climate (high desert) I can answer to definitely use interwoven felt (for shakes, anyway, can't answer for shingles). Our house and detached garage had 30 year old roofs when we replaced them - the house had interwoven felt while the garage did not. Both had skip sheathing. Standing in the attic of the house you could see daylight looking down between the shakes, but almost no evidence of water in the house. The garage needs to have all the drywall replaced due to extensive water damage.
I don't have any experience with CCA treated roofing, but it's my understanding the three companies on this continent that pressure treat lumber with that stuff have recently agreed to voluntarilly stop producing it in exchange for immunity from class action lawsuits in the future. It's bad stuff - like asbestos, or lead.
jimbo.. IMHO.. it's not bad stuff.. the treaters just decided they weren't going to spend the rest of eternity trying to defend in court... part of the new "pseudo -science" ..
course i cud be wrong..
but hey, whadda i no ?Mike Smith
Rhode Island : Design / Build / Repair / Restore
Mike - you said ".. IMHO.. it's not bad stuff.." you got a right to your opinion, and another right to express it. No problems there, mate.
'corse, you obviously have you head up your ass.
Hey! I just saw a photo of all those state commemorative postage stamps they're gonna issue. How come the one for Rouges Island has that same bunch of pirates in a sail boat as the quarter has? Is that all you guys got in that little state? Oh, wait a minute! I got it! You guys could show a framed ceiling with STRAPPING! Yeah, that would be a PERFECT representation of that state.
mamasboy
The thickness of the shake combined with the 3/16" to 3/4" gap left between them allows airflow up undr to vent with the interwoven felt.
I would conjecture that you were told it is acceptable to lay triplecourse without felt because CCA is not supposed to rot anyway. Still not good waterproofing practice to do away with the felt. Why?
Well, the treated would be heavy, pond dried, wood. When it finally dries up on the roof, it will shrink and become brittle, likely openning splits in the wood near the nails. Now you've got a bunch of CCA kindling. It might keep most of the water out on a steep roof but not on my dime. Do you really want a steady wash of heavy metal coming off your roof onto....for the next ....years?
Realize that when talking to the rep that what "can be done" is not the same as what is "most often advised" or "best" not that someone in that position would be allowed to use a word like "best".
Mikey and Jimmy, thank you for teaching fred and I how to play together well!
Excellence is its own reward!
Edited 4/11/2002 9:51:27 PM ET by piffin
Yeah, well, it helps if you've seen the crack of dawn from the first tee together.
If you can say one thing definitively, it is that all cedar is not created alike. From the best of the best mills in BC to the worst of it there is a LOT of variation. That, along with installation, explains some of the differences in performance. Overhanging tree areas will decrease the life of the roof too.T. Jeffery Clarke
Quidvis Recte Factum Quamvis Humile Praeclarum
"Overhanging tree areas will decrease the
life of the roof too."
That depends Jeff, If it keeps the roof damp by dripping dew onto it, the rot can happen quicker, but I re-roofed one where it was obvious that the trees had added to the longevity. Very tall cedars on the south side of the house that didn't directly overhang enough to contribute to moisture but did provide shade and kept UV rays from deteriorating the lignans.
Around here the south side of the roof will wear out more quickly than the north by far. On this one the thirty something year old cedar shingles looked almost new except for colouring. The north was well worn from the winds.Excellence is its own reward!
geez...cant imagine I just sat and read a thread so long about CEDAR BREATHER and the such....Whatever happened to roofing igloos?
Fred, you speak in several of your postings about scientific studies. What study did you do that allowed you to conclude that Cedar Breather actually caused a roof failure? The product has been on the market for over 12 years. I would think if it caused failures it wouldn't be doing so well by now. The Cedar Shake and Shingle Bureau sees fit to recommend it in their manuals as an application alternative to skipped sheathing when using a solid plywood deck. Obviously, there are other, more labor-intensive options for providing air movement under shingles or shakes that may or may not work just as well. As for flashing details, there are some details in the company literature, which look like drawings from the Bureau literature. I would think it's tough to cover all flashing details someone may encounter in the field. I would think a qualified roofer can handle those types of situations.
Dear Jeff,
I'm not going to argue about weaving felt into the courses. But if you want to use the "Cedar Bureau" as a paradigm for best practice, then we have something to debate.
Error #1--They neglect to show an exposure dimension in their graphic, but it scales wrong anyway. I think the exposure of should be limited so that there is always 3 layers wood roofing throughout.
Error #2--They neglect a third course at the eaves. Again, this leaves inadequate protection where the roof needs it most.
Error #3--Only a single layer of underlayment is shown at the eaves. This is clearly not acceptable in any northern climate, but bad practice in any wood roofing assembly. Note how every other part of the roof they show has two layers? I like that better. And where would that protection be more important than at the bottom. That's where the greatest exposure to water is. Always.
Error #4--"The felt interlays also increase the roof’s insulating value." That is laughable. But it is effective at suppressing interstitial evaporation and keeps the cedar wet far longer. When the underlayment is bomb-proof, that's not a good trade.
Error #5--Roof after roof after roof shows that any type of poisoning, a bit of metal ion off flashing, or the alkaline wash off brickwork, or direct chemical treatment does far more to preserve cedar roofing than ANYTHING mentioned at the site you linked to.
Generally speaking, you've hit upon a nice example of an industry group putting out less than state-of-the-art information about their product. This is fascinating topic all by itself. I hope to see more examples and some serious discussion about that sometime. But for now, I'm sticking to advice that I can verify on the roof. The Cedar Bureau folks seem to be afraid of heights.
Regards, Fred
[email protected]
Definitely with Jeff on this one. The proper way to install a shake roof is over skip sheathing with shake felt at each course.
If local code requires solid sheathing, then cedar breather or furr strips is the best alternative.
Properly installed a shake or shingle roof will keep your house dry and last a long time
david
walk good
Please note that the 'authority' states: "A solid deck is recommended in areas where wind-driven snow is encountered." Also note that eaves, even with skip sheathing, are always solid with ice & water shield. If that's ok with eaves, then why not run the ice and water from eave to ridge and use cedar breather on top of that? I've had no problems with that method.T. Jeffery Clarke
Quidvis Recte Factum Quamvis Humile Praeclarum
Jeff,
some confusion with terminology. In the cedar bureau illustration, using board sheathing is called solid sheathing, yet in their written instructions, they state solid sheathing is to be considered plywood only.
in my mind solid sheathing is plywood , engineered sheet products. Board sheathing is just that , wood boards used as sheathing. It may become a solid deck when run tight together, but it has different propertys compared to plywood sheathing with consideration to moisture, air movement and drying time.
For windy exposure, the skip sheathing was often run closer together, but the interwoven shake felt on each course was the key to maintaining roof integrity, not solid sheathing.
Your idea of running ice and water shield clear to the ridge is superfluous unless you install your shakes incorrectly.
Discussed the use of solid sheathing with the CB several years ago and came away with the impression it was more to do with code compliance and engineering requirements than performance concerns. If cedar breather works as well as some people claim, then using solid sheathing may be acceptable. I would still weave my shake felt to prevent moisture from driving into the shakes and running down the solid sheathing.
I lke the breathability of board sheathing/skip sheathing. If care is taken in the install of the roof, flashing details, materials etc,then there should be little problem with a lasting shake roof.
david
walk good
David - the confusion may be due to the fact that they show skip sheathing in the diagram with solid boarding at the eaves (correct) as opposed to plywood solid sheathing full height. They don't mean that in a skip sheathing situation you should use ply at the eaves.T. Jeffery Clarke
Quidvis Recte Factum Quamvis Humile Praeclarum
I'd second what Jeff, Mike, and Piffin have said. It will breathe better than you might think in spite of the felt. In years past I've heard complaints about higher a/c bills from folks in Texas who have replaced their cedar roof with solid deck/ comp shingles. Pay attention to the fasteners ........... Jeff's expert authority has good advice there, too. Makes a beautiful roof imho.
Edited 4/8/2002 8:20:07 PM ET by jc
OK i am jumping right into this one. I have installed many a shake roof and consider myself an expert. But what do I know? I think cedar breather is ok. But just ok not the best option. If given the time to do the job any way I want with the best job in mind , I would , Install 6' of Ice/Water shield to all eaves. Install 30lb felt to rest of roof decking (sheathing if required) . Install horizontal strapping over vertical and install shakes doubled coverage if over 7 pitch, triple if under, with 2 " ring shank stainless steel nails. Copper for all flashings. I would vent the ridge and the bottom facia , with a bug screen as to allow the roof to breath underneath. Horizontal strapping on rafters would be my second choice. Cedar breather on sheathing third choice. All with at least 30lb felt interwoven on each coarse. I would never install shakes directly to the sheathing or leave out the felt. Nor would any good roofer. I have nothing against the cedar breather and will use it again but it is expensive and not as cost effective as my best option.