Standing Seam on new construction

Guest User
8/5/2013
I am an experienced building designer, but doing a standing seam metal roof on a client's custom home for the first time. The roof is 3:12 pitch, and will be plywood decked. Some rooms have vaulted ceilings, but I want to "cathedralize" the insulation in the rest of the house too. We are in climate zone 5, in the high desert, with winter snow but not much overall yearly precip. Daily temperature swings in the summer can be 40 degrees between day and night. 1. What sort of underlayment should I call out? Or does that depend on the specific manufacturer's metal panels? 2. Oregon code doesn't call for I&WS under metal roofing as it does for asphalt and comp. I plan to call it out anyway. On asphalt roofs we use it from the eave edge to 24" inside the wall line, and at valleys. Will this be sufficient under metal? 3. How likely is it that a specific manufacturer requires their product to be installed over strips, and if that's the case, can the strips be laid over the underlayment which is on top of the solid sheathing? 4. Any other advice you can give me? I've read several threads here - you guys are great!
Info @windowsonwashington.net
An informed customer is our best customer.
8/13/2013
Viki, Please feel free to email me directly if you have any other questions. Here goes: 1. Best to confirm with the panel maker but I prefer the synthetic woven polypropylene options. 2. That is sufficient. Be sure to specify a high temp and non-granulated type. 3. All depends on the panel manufacturer. In most cases, the applications can be done just as you specify. 4. I would recommend that you look at the insulation schedule in the design. If you know you are running metal and will have an insulated roof deck in some parts of the cathedral ceiling, I would look into the incorporation of rigid foam to the outside decking surface (i.e. create your own SIP). This will eliminate much of the thermal bridging and make for a more efficient roof/insulation system. Eric Novotny
V Cijunelis
11/24/2013
I am in a similar situation. Z5, chicago area. 3:12 and 4:12 shed roof pitch design. We are looking at berridge standing seam with consealed fasteners. Cathedral ceilings everywhere using TJI 14" joists 24" oc. Insulation is the concern, no one seems to know what to do. Here is what we are thinking to control moisture and dewpoint SS metal, light gray, 3:12 slope 15# felt Wood sheathing on TJI 1) blow 11" of ocSPF directly to inside of sheathing (no venting) and then mount the gypsum 2) tablesaw cut 2" rigid polyiso to 1' 11-3/4" wide strips, wedge then into the TJI cavity at top leaving the 1-1/2" vent from the top TJI plate asventing, then blow a couple inches of ccSPF then put in unfaced batts to make up the rest of the R needed, gypsum over that. Exterior rigid is too costly, subs are not familiar with it, which will likely cause issues, etc Any opinions/guidance is appreciated.
Info @windowsonwashington.net
An informed customer is our best customer.
11/24/2013
Answered in the other post.

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