Roof layers over an existing vaulted roof

Craig Stout
Craig
2/21/2012
Hello - I hope you can help me. I am in the process of renovating a beautiful 1930's panabode cabin and we discovered that it had a gorgeous fir roof that we want to expose. The fir roofing planks are held up by stringers running lengthwise, and over top of the fir, is just asphalt shingles, with a metal roof put over that. What we want to do is strip the metal roof off, strip the asphalt shingles off, and the then reinsulate and finish with a nice metal roof (works best for our snowload etc). What layers would you recommend to put over the fir and would you recommend some type of airflow in there as well? Many Thanks! Craig
Todd Miller
Classic Products, Inc.
2/21/2012
Sounds like a good project. Tell us more about the space beneath the roof ... what sort of attic space and ventilation is there? Why do you feel the need to put insulation on top of the roof rather than on the attic floor?
Info @windowsonwashington.net
An informed customer is our best customer.
2/22/2012
Post up a couple of pictures and I will give you what my exact recommendations would be.
Kris whittington
2/24/2012
I am having a 24 guage metal roof (16 inch standing seam) 45 year Kynar 500 (Metal Sales brand) installed on my home. I told the contractor that I wanted the best of everything as far as materials and installation practices. The roof has a 10/12 pitch and the roof rafters (2 x8) make up a vaulted ceiling on the inside of the house. The rafters are 16 on center and have Styrofoam vent running up each rafter from the birds mouth to the attic space (which is approx 3 high and 8 wide). The roof decking consists of 1" cdx - I had 1/2 inch before and did a complete layover with an additional 1/2 inch for strength. Prior to the install, the trouble signs appeared - the roofing crew installed the felt paper vertically not horizontally, then they proceeded to instal the synthetic underlayment the same way using nail caps to hold the underlayment down. Because I wanted the best, I purchased 3 rolls of double bubble insulation which was installed on top of the synthetic underlayment. The panels are 16 inch striated panels with UL 90, 2" clips holding them down. My questions are as follows: (1) Shouldn't the felt and underlayment have been run horizontally not vertically? (2) There is no gap between the double bubble and the metal panels - shouldn't there be 3/4 to 1 inch gap with purlins installed on the roof decking? (3) Doesn't it defeat the purpose of having the double bubble if you don't have an air gap? (4) Because the metal is being laid directly on a vaulted ceiling, wouldn't that be all the more reason to have an air gap (and I believe this is code although I would not know where the code is located or how to cite code)? I am thinking these issues should be fixed (or, in the alternative, the company be fired) - what do you think. The contractor knew what I expected and agreed in writing to use the highest quality materials and workmanship (and to comply with all industry standards and codes) but this does not appear to be the case. Any help would be greatly appreciated - I am in the middle of the job and would like any suggestions as to what you, as experts, would do. Thank you!
Todd Miller
Classic Products, Inc.
2/24/2012
Kris, great questions. There are a lot of dynamics to this and much depends upon exactly what you want to accomplish but I would like to see a vented airspace ideally and I also feel underlayment should run horizontal. Have you contacted Metal Sales? They are good folks and will help you I am sure.
Kris whittington
2/24/2012
Thanks for the input, I don't want to change contractors but the company really does not seem to care much about quality. The job site is left horrendous, with construction debris abound, metal and wood left uncovered, and the metal already is showing significant signs of oil canning when viewed up close. The metal is contouring to the unlevel roofing deck. I asked the contractor if we should have used purlins across the roof decking to level up the install surface and for ventilation purposes and he acted as if it was not necessary. Now the metal has been on only 2 days and it bows with the roof. In my mind you would fir the purlins to the highest point on the roof and create a level surface across the deck and create an airspace at the same time. Again any comments are appreciated and thanks for your time and help. Kris Whittington
Todd Miller
Classic Products, Inc.
2/24/2012
I understood I think that Metal Sales is the manufacturer of your roofing. Please correct me if not. I think that taking your concerns back to the manufacturer of your roof is the best way to accomplish something positive.
Info @windowsonwashington.net
An informed customer is our best customer.
2/25/2012
Sounds like a bit of disaster so far. You are correct that the felt (and more ideally synthetic underlayment) should have been laid horizontally. Radiant barriers do need and air space to work otherwise they are useless. This would have been (20/20 hindsight is always perfect) the time to put down rigid foam and really insulation and fix the venting on the vaulted ceiling. Trying to level out the roof deck with purlins are very difficult and the metal will ultimately translate the shape of the roof deck. This would have been a scenario where a new plywood deck, for multiple reasons, would be preferred. An air (vent) space behind the metal is an effective application but not necessarily a must depending on how the venting and insulation are done. What is the feedback and tenor of the contractor?
Guest User
2/27/2012
Thank you for the reply. I was out of town working all weekend so I did not see your post until this morning. The contractor pays lip service but never changes anything. I came home the last day the crew worked to find mud in the end of a new panel and materials (plywood and metal laying in in the yard) unprotected. I understand the roof will work but my problem is that money was not a barrier on this job. The roof is slightly more than 11 squares and I made it clear I wanted it done correctly and would spend what it took to do so. I knew the deck had some low spots but wanted to do the best I could with what I had to work with. I fixed the interior roof slope several years ago (on the same slope) with furring strips and there was a drastic improvement on the drywall. Now I understand metal may not be as forgiving but my main problem is some low spots in a couple of areas which, in my mind, could have been mostly corrected with proper care. Since the entire deck has had a layover already, the only way to correct the problem which was from improper crowning of the rafters would be to install new rafters, which I can't swing at this point. With regard to the venting situation of the rafters, there are egg crate Styrofoam vents from the birds mouth to the attic which are fed by soffit vents and there will be a continuous ridge vent with the new metal roof. My thoughts are that striated panels may provide a little more airflow than a flat panel but not sure if this holds true or not. Oddly enough, I told the contractor I wanted the flat panels but when he arrived with the materials the panels were striated. My suspicion is he knew there would be issues with oil canning because of the roof deck and thought striated would be more forgiving in a less then perfect install. One last question pertains to the UL 90 clips and the 1" pancake screws being used to mount the clips to the deck. Are these long enough to make a solid bond to the first 1/2" of plywood. Knowing these guys, they probably did not even attempt to hit the rafters when they did the layover with the new 1/2" plywood. If some pics of the set up and install would help, I'll gladly upload some. Thank you for your time and response and any help is greatly appreciated. Respectfully, Kris W

If you would like to reply to this thread, please log in. If you do not have an Ask the Experts forum user account, create one here.

Find a Contractor

Get Started Today

Take the first step to increasing the value of your home with a great looking, durable, fire resistant and energy efficient metal roof. Browse our list of qualified MRA Member Roofing Contractors in your area for a free consultation and estimate.