I’m looking at re-roofing our home. I’m putting together a bid package. The present roof is 19 years old. Three tab fiberglass/asphalt shingles. The shingles have a 25 year warranty and are in fair shape. I have lost some tabs because of wind and have replaced them yearly as needed. I have not replaced several that I lost over this past winter. The trusses are 6/12 pitch and 2 x 6 construction on 16 inch centers. They are designed to span the width (36’) of the house, and there is a center load bearing wall. The roof decking is ½â€ plywood with 30 lb. felt and in good shape.
We would like the new roof to be a cedar shake roof. (¾â€ heavy 24 lg., 10†exposure). Can it be done without a tear-off? I have been told that the weight of the shakes would be 300 lbs per square. Has anyone had experience with this type of project before? Are there any specifications available for doing this type of project? I’m also looking for more information and details so that I’m sure the job is done right. Details for around skylights, chimneys, roof vents, etc? Can a ridge vent be used with cedar shake roofs? Is there anything that I forgot?
Replies
In my neck of the woods (California), many communities don't allow shake roofs any more. They're a fire hazard, both to themselves and to their neighbors.
Depending on how long you want to live there, I would do a tear off, unless you plan to sell very quickly. The Shake won't be easily nailed to asphalt shingles and won't lie flat. A tear off will look better.
I recommend using ice and water shield around all valleys, perforations and the first 6 feet or so on the eaves, whether you are in a cold climate or not. Now is also the time to think about gutters.
Regards,
Boris
"Sir, I may be drunk, but you're crazy, and I'll be sober tomorrow" -- WC Fields, "Its a Gift" 1934
Cedar Shakes are normally installed over skip sheathing to allow the shakes to breathe and dry out after getting wet. There is a product called Cedar Breather http://www.obdyke.com/html/products/cedar.html that I would use because of your solid sheathing. In any event, a tear off of the asphalt shingles is in order imho. The Cedar Bureau's website http://www.cedarbureau.org/ should have the installation details you are looking for.
First if you are gonna do a shake roof don't compromise. the biggest expense is labor so make sure it's gonna last.. improperly installed shake roofs won't last as long as a shingle job.. and will look bad in too short of time..
Tear off. and use cedar breather under the shakes.. otherwise the moisture will stay on the shakes and cause premature failure..
Use copper at least on the ridge. it will afford you a measure of protection against mold forming.. Make certain that stainless steel nails or staples are used.. While some advocate hot dipped galvanized, if the dip is knocked off the nail will fail and with it the shake..
My experiance? well I'm doing it now (or was before I took a break to come inside)
jj
Don't listen to everything you hear, even from me.
;)
But if it were mine, I would probably do the following to get where you want to go. (I roofed for over twenty years, probably a quarter of those roofs were cedar shakes and shingles.)
I would apply skip sheathing right over the asphalt shingles. 1" x 4" @ 10" OC. Nail or screw it into the rafters. Then install the shakes with 30# felt woven in to the courses appropriately. This method will save the tearoff trouble and expense and give the required breathing and nailing for the shakes. it will provide you a "cold roof and lessen your need for attic ventilation. Wheather or not to add more ventilation than you have would depend on another dozen variables I can't see from here.
Put the ice and water shield in valleys before the skip sheathing and the metal after.
Couple more things...
It sounds like you have rafter framing and not trusses lkike you mention. Trusses need no center bearing wall and generally are made with a 2x4 top and bottom chord and are installed normally at 24" OC
You mention putting together a bid package. Don't waste your time getting too official like that untill after you've talked to a couple of roofers. Use the advanced search function here and read threads about "bids" or "bidding" for discussion of why you are more likely to get a better job for the money if you don't do "bids"
Excellence is its own reward!
JJ,
Already got some good advice.
Shakes are an expensive roof. There was a study in one of the trade rags and I think it was the most expensive alternative. I tore of an shake roof recently and it was only eighteen years old and mush. If you're not under trees and its properly installed you may fair better.
Around here a properly installed shake roof on cedar breather can run a grand a square.
I would tear off the shingles although the previous poster had mentioned a viable alternative with the furring. Not sure how much cold roof venting action you would get running the furring horizontal, but that is an acceptable method. For the amount of work it would be to tear off the asphalt, you don't want to be the unlucky slob that has to deal with it in the future.
Definitely skip sheathing or cedar breather, though.
For all the specs go to cedarbureau.org.
Tom