I am building an addition to the back of a house that has a cedar shake roof. I have not installed a shake roof before but the new roof is small and I wanted to add to my skillset.
Current construction on the house is a truss roof with a vented attic. 1/2″ plywood decking covered with roofing felt, medium handsplit shakes at a 10″ exposure woven with 18″ felt over each course. Shakes are stapled with 2 staples per shake.
I believe the existing roof is fairly recent (within the last 5 years) obviously the shakes have weathered, but the ones I removed during demo are still “red” in the center.
My question(s) arise from reviewing the Cedar Shake Bureau website. They state that in humid climates (and I think Iowa qualifies) the shakes should be installed using a breather mat over plywood to allow both sides to dry evenly.
The existing roof does not have the breather mat, and I am uncertain if this will reduce the service life or if the existing felt will allow the roof to perform acceptably. Would it be advisable to include breather mat it in the addition?
The addition roof is likely to outlast the existing just due to age, but I would not want to repeat a mistake (if one has been made) on the addition.
Also, can I install felt on the entire deck of the roof prior to installing the shakes? Then interweave the shakes with felt on each course, or am I potentially creating a problem with too many layers of felt?
Finally, any opinions regarding the use of staples v. nails? I would think the staples would be faster, especially since I own that equipment, but nails could offer better holding power. My new roof deck is 5/8″ cdx plywood.
Thanks in advance for any insights or advice.
Replies
Seldom do I see here a series of questions relative to a project so well presented, researched, and thought out.
well done
Now let's see if I can do them justice...
The breather is not a necessity. we did ccedar for years before it was invented,
But the shakes will last longer if you use it appropriately.
The question is will the added life be equivalent or greater than the ost of the breather, which is not cheap.
I have never lived in Iowa, But gven the extreme old in winter, I don't know if it is as humids as Georgia or Florida. You won't see many cedar roofs down there, period.
The way I ran shakes was to dryin entirely with 30# felt, then - knowingf aprox how many squares I was likely to run that day, roll out the 18" interweave, nailing at tops only. You plan that layout so that the bottom of the interweave stripos is where you want the bottoms of shake courses to lie. I'm sure you can see this from what you have now. With 24" shakes, the top 4" of the shakes will be covered by this felt strip. You can see it between pairs of shakes, and that helps orient the next course up.
So after the interweave is run out, I stock the work area with bundles . That helps weight the interweave down so wind leaves it there, and places the shakes approx where I will use them, about every four feet as I recall.
Laying the shakes mens slipping the top tip of each in under that four inches worth of interweave and nailing. Don't forget startter course.
I almost always hand nailed and ran from one to three squares a day tht way. When I used a gun, I got up to six squares sometimes on open running.
I hate stples, but i've been told they are acceptable. With either, it is important to adjust the gun so the fastener is not penetrating the cedar.
I did not give a full answer to whether you use cedar breather. That one is up to you. It depends a bit on the pitch of this roof. Steeper sheds water faster and is less likely to stay damp.
My inclination is to not use it here, because when the rest of the roof is shot, this addition most likely will get re-roofed at the same time by whoever owns it then
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Taunton University of Knowledge FHB Campus at Breaktime.
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Piffin,
Thank you for the kind words. I read your reply this morning, but didn't have the time to reply as I was running late.
I think that I will omit the breather and install the interweaves as you noted. The breather is about $120.00 for 200 sq ft. my total roof is only 6 square so not a huge cost overall, but I don't think the potential extra lifespan is warranted on just the addition.
Thanks for the install tips. I will install the 18" strips as you mentioned.
This roof is pretty cut up for only 6 squares. 1 ridge, 2 hips, 2 valleys, and three skylights. In addition, I have to weave into 2 existing roof planes so I doubt that I will be anywhere near your production rates, but it sure will be fun ;).
Any advice on how to remove shakes on the existing roof without causing major damage? I'm inclined to start at the top and work down, but this causes me to remove more shakes than I would like.
One final question, what is your opinion on the necessity of venting the roof deck below these shakes? The construction is 16" TJI's at a 6:12 pitch. Top flange of the TJI's is roof sheathing, bottom flange is sheetrock ceiling. Plans call for soffit and ridge vent with a min. 2" air space below the deck, with the balance of the cavity filled with insulation. I question the effectiveness of the venting.
Attached is a pic to help.
Thanks
Given my age and how cut up that is, I could not match my former speed. Be good going to get one square a day with all the cutting and flashing!There is barely any roof above that tie in, so I would remove all of it to the ridge. easier by far than tying back in and chancing a leak!The venting description sounds fine to me, but use a good snug VB on the inside between the Ijoists and the sheetrock. That way no moisture gets to the insulation space so none really needs to be vented out
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
Beautifully put, as noted.
I would suggest some reading here http://www.cedarbureau.org/faq/installation.htm and here http://www.cedarbureau.org/installation/roof-manual.htm if you like.
Jeff
Edited 11/5/2007 9:28 pm ET by Jeff_Clarke