Cedar Shingles Directly Over Rigid
Continuation of previous thread…It is difficult to resurrect an old thread….See above link for previous discussion.
Has anyone tried using typar w/ homeslicker (or the TYvek Drain Wrap product) over the rigid and attaching the shingles directly over the typar, fastened through the rigid back to the sheathing w/ 2.5″ ring shank nails?
JLC had an article with this application a few months back except they were only using 1″, which has been noted in this discussion as not appropriate for this climate. They list the upcharge as being 9-10k (not clear if that only accounts for rigid, sealing rigid and building paper or if it also includes cost for new window trim). The estimate seems pretty high if is only includes material and labor directly related to the rigid and wrb.
Any thoughts on how this system might perform…curious how the shingles would hold up if the “bite” of the fastening is 1 3/4″ back….
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The Tyvek drain wrap doesn't give you enough air space and the Home Slicker is just way way too expensive. It's cheaper to strap the foam with 1x3s nailed through to the studs or, in a hurricane zone, 3" strips of OSB or plywood nailed back to OSB sheathing behind the foam on the studs.
The key thing is to allow for air circulation behind the shingles, in at the bottom, out at the top according to research done by Straub and Lstiburek at BSC. with horizontal strapping behind shingles that would imply some intentional gaps at the butt joints and a bug screen at the bottom and top.
We've done horizontal strapping with OSB scrap and it goes very fast and we were able to get a lot of the strips out of stuff that would have been wasted otherwise.
Cedar shingles are traditionally installed with 4d or 5d galvanized box nails. Where are you going to find 8d ring galvanized shank nails that wont split the shingles?
Cedar shingles should be nailed directly to wood backing, whether sheathing or horizontal furring strips. They are naturally self-draining and self-breathing and need nothing more than #15 felt paper as a secondary drainage plane behind them. They should not be applied over foam board.
Good suggestion on using the osb for strapping.
Are you find there is enough of a gap in the system to allow bottom up circulation with horizontal strapping? Are you find strapping goes fast enough to not warrant simply adding another layer of sheathing?
Any thought as to your additional materials and labor cost for adding 1.5" foam, strapping and any other work associated with the upgrade (flashing, insect screening at base, taping seams etc.). Are you using the face of the rigid as the drainage plane?
"finding"
Don't you worry Robert, I've got the perfect nail for the job.
Typically, we use a stainless steel ring shank nail for cedar sidewall or sometimes a stainless staple.
I staple shingles when siding. Fast install.... low cost, hold well, and DO NOT SPLIT SHINGLES. If you use other fasteners go for it. My way works for me.
Chandler has your method for over foam.
Any specific thoughts on the JLC article...did anyone see it. Because they installed the singles directly over the homeslicker through the rigid insulation and back to the sheathing. Sounds like no one here is too excited about that technique.
It was from the April 2010 issue.
I am in agreement with the JLC article 's comments. As stated in the Green Building Advisor forums, thicker rigid insulation is necessary in that climate zone:
https://www.greenbuildingadvisor.com/community/forum/energy-efficiency-and-durability/15208/explain-correct-usage-rigid-insulation-exteri
JLC comments on the April 2010 article:
http://www.jlconline.com/cgi-bin/jlconline.storefront/4c224cd700599f0327190a32100a05ad/Product/View/1004buil
So you agree with the concept described in the article with the exception (as noted in the comments) of the use of the 1" thickness as opposed to at least an 1.5"....
I do not agree with the shingle fastening through any rigid. I was leery about using 1 7/8" galvanized stapes over Homeslicker!
I am in the middle of the same process on my own home; removing hardboard siding and sheathing to pull out 2" of Rock Wool from the 2 x 4 exterior walls. I am replacing with blown-in cellulose from the exterior (interior walls are plaster), Padding out all windows with local backprimed pine trim, 2" XPS, joints taped and a new layer of 1/2" CDX plywood screwed through the rigid into the studs. Homeslicker plus and eastern white cedar shingles finish it off. One side a year - a very time consuming process especially when weaving corners.
That being said - I would never even consider installing shingles through foam or ripping OSB (poor nail attachment) or CDX plywood strips at 5" on centers. Too much work!
Jon We generally install 18" red label shingles at 8" spacing and since most of our roofs down here are hipped we often end up with piles of OSB triangles at the end of a roofing job so we have strong incentive to use up the OSB as strapping rather than burn it or send it to the landfill. I agree that 1x3 would be better strapping than OSB but since the OSB is essentially free and we're only using it as a spacer it works well for us. The three inch strips are so light and flimsy that you can cut them on the ladder with a jig saw or cordless sawzall. so the added time on the shingle install is really very negligible. gaps are fine, you want to encourage vertical air flow and you're just stapling through the foam to the underlying OSB. Maybe it's not the very perfect-most way to go but it gets the job done well enough, especially considering that we generally are working under a 37" roof overhang so these shingles only get wet with severe storms so we don't have to put any paint or preservative on the shingles at all.
I agree with Robert that the shingles are naturally self-draining and self-breathing though I still tape up my house wrap really well rather than using tar paper only. I like to run 15# tar paper over my house wrap under the shingles to keep the surfactants in the shingles from damaging the wrinkle-wrap when we are applying them directly to the OSB sheathing without poly-iso and strapping.
We use the 1" crown x 2" leg galvanized staples and have not had any issue with pull-out from shingles in OSB. I think you have to agree that the HomeSlicker is very expensive, More per square foot than the OSB last I checked. Your method is very, very good but expensive to execute. What is your roof overhang? You must have a lot more weather exposure than we do.
Michael,
I am not completely against OSB
Using OSB as a horizontal furring strip in a drainage space does sound disturbing.
The Edge of the OSB is the "Thirstiest" part.
And the part that is most likey to pucker up and grow and grow.
True, A 37 inch overhang "helps" if walls are not very tall...
Do you change to real wood furring for 2 story walls and gables?
John That's not a situation I've encountered yet but I agree that it would be worthwhile to switch to the real lumber in an area that would get much weather. My rule of thumb is to invest in the best waterproofing you can afford and then don't let it get wet.
Michael,
Thanks for the info - it is a good idea to reuse material and eliminate waste but I'm not a fan of OSB, especially in this kind of situation and with $7,000 worth of shingles. My cape roof overhangs were originally 12" but the plans are to add rigid to the roof and extend the fascia and rakes when it's time to reroof in a few years and as economically feasible. Our 1941 30' x 40' three quarter cape has actual 2 x 6 rafters at 24" o.c.