arkie, I just noticed this as an alternate bid on the plan: "1/2" gyp over 1x4 furring strips 16"oc over 1" foil face polyiso rigid foam ins applied to underside of roof rafters" I'm feeling pretty good about the roof stack for this home now thanks.

Do I need the furring strips under the metal roof if I use a standing seam roof that has raised ridges in it for venting purposes?

Most standing seam metal roofs require a solid flat deck unless you buy the very thick and expensive commercial grade metal. So, in general, you won't use furring strips with a standing seam metal roof on a residential application. This is where the roofing felt is particularly important. I would use the heavier #30 felt if you have the vent channels under the decking and have venting intakes at the soffit and exhaust at the ridge (the wood decking will need to be installed ~1" shy of the peak on both sides to allow the hot moist air to escape). Most metal roofing manufacturers have ridge caps and mesh material to fit between the raised ridges that allow air flow but keep the bugs out.

Hello Dana,

I was wondering , where i could get some info on screw spacing for the system you mentioned.



"For insulating at the roof deck you'd be better off with R20 in rigid polyiso (3.5") above the roof deck, and using 2x purlins through-screwed to the rafters with timber screws on which to mount steel roofing, and doing the rest with either open cell foam or tightly fitted R23 rock-wool batts on the interior side."

Any pointers very much appreciated.

Posted By ColdNorth on 25 Aug 2013 11:32 AM
Hello Dana,

I was wondering , where i could get some info on screw spacing for the system you mentioned.



"For insulating at the roof deck you'd be better off with R20 in rigid polyiso (3.5") above the roof deck, and using 2x purlins through-screwed to the rafters with timber screws on which to mount steel roofing, and doing the rest with either open cell foam or tightly fitted R23 rock-wool batts on the interior side."

Any pointers very much appreciated.

In my opinion, you would want a screw through each purlin where it passes over each rafter.  You want the screw to penetrate ~1-1/2" into the rafter.  I wouldn't want to rely on just through screwing the purlins into the decking which is likely anywhere from 7/16" to 5/8" thick - not enough screw holding ability with a screw every 16"-24".  You don't want a strong wind sucking your roofing metal and purlins off.

Make sure the metal roofing you select is capable of spanning across the purlins without bending in the middle when someone walks across it.  Some types of metal roofing require that it be installed on a solid flat deck.

Posted By arkie6 on 25 Aug 2013 10:35 AM
Most standing seam metal roofs require a solid flat deck unless you buy the very thick and expensive commercial grade metal. So, in general, you won't use furring strips with a standing seam metal roof on a residential application. This is where the roofing felt is particularly important. I would use the heavier #30 felt if you have the vent channels under the decking and have venting intakes at the soffit and exhaust at the ridge (the wood decking will need to be installed ~1" shy of the peak on both sides to allow the hot moist air to escape). Most metal roofing manufacturers have ridge caps and mesh material to fit between the raised ridges that allow air flow but keep the bugs out.

I don't want to get the expensive commercial metal roof for obvious reasons. I guess I'll use the #30 felt as you state. That will make it easy. Ok thanks guys.

#30 felt is extremely vapor-tight nearly a class-I vapor retarder, and shouldn't be used on a deck that isn't vented from the underside. Design and understand your roof stackup before committing to it.

#30 felt also isn't always a correctly rated slip-surface underlayment for metal roofs- read the manufacturers specs on what the roofing really needs when mounted flat onto a deck.

arkie6 correctly asserts that you need 1.5" of penetration into structural wood for the timber screws.

Putting a vented deck on furring over the foam through-screwed to the rafters 24" o.c. with timber screws works too, and you can mount the metal roof onto the vented deck.


You can also do it with a secondary deck flat to the foam through-screwed to the structural deck:

http://www.finehomebuilding.com/assets/uploads/posts/20940/H224ES_85.jpg

http://www.finehomebuilding.com/assets/images/pages/roofing/energy_retrofit_opportunity.jpg

There is some potential for trapping moisture in the secondary deck with that stackup though.

Dana we were planning to do a vented roof. I am not sure the budget will afford the full R20 exterior polyiso with unvented roof.

Posted By Thermal Shell on 25 Sep 2013 06:18 PM
Check out: www.buysipsonline

TS,
I did check out your website and not sayin' your guilty of plagiarism or anything like that , but your "Meadowbrook" model is an exact depiction of my "Ashland" model that I built in Louisiana (see link below) You may want to be careful of copy right laws , I am sure that the brochure you borrowed it from was copy righted, if you did not get written permission to use those plans and elevations you might get sued
Ashland Model

Posted By cmkavala on 25 Sep 2013 09:13 PM

TS,
I did check out your website and not sayin' your guilty of plagiarism or anything like that , but your "Meadowbrook" model is an exact depiction of my "Ashland" model that I built in Louisiana (see link below) You may want to be careful of copy right laws , I am sure that the brochure you borrowed it from was copy righted, if you did not get written permission to use those plans and elevations you might get sued
Ashland Model

It could be that the home is somewhat "cookie cutter" looking and therefore looks the same? I've seen that type of model/design home more than once in my lifetime. There are homes in Phoenix that have that design theme but they use stucco instead of a brick facade.


With that being said, judging from all the spam posts by "TS", I would be skeptical of their practices. Over a dozen threads were spammed today by him.

Posted By Lbear on 25 Sep 2013 11:01 PM

Posted By cmkavala on 25 Sep 2013 09:13 PM

TS,
I did check out your website and not sayin' your guilty of plagiarism or anything like that , but your "Meadowbrook" model is an exact depiction of my "Ashland" model that I built in Louisiana (see link below) You may want to be careful of copy right laws , I am sure that the brochure you borrowed it from was copy righted, if you did not get written permission to use those plans and elevations you might get sued
Ashland Model

It could be that the home is somewhat "cookie cutter" looking and therefore looks the same? I've seen that type of model/design home more than once in my lifetime. There are homes in Phoenix that have that design theme but they use stucco instead of a brick facade.


With that being said, judging from all the spam posts by "TS", I would be skeptical of their practices. Over a dozen threads were spammed today by him.

Lbear,
trust me when I tell you it is an exact copy