Install Questions for Attached Patio Roof

Kyle Finke
1/11/2017
I'm building an attached patio cover to our home. With a low soffit and fascia, I chose to attach the patio cover several feet up the roof line so that it would terminate at an acceptable height. The house roof is 4/12 and the patio cover is 1/12. I'm planning on using Galvalume Plus PBR as the final covering, no paint as very few people will be able to see the finished product. The roof deck is 7/16 OSB sheathing over 24" o.c. rafters, extending 24'0" from the house and is (mostly) 23'0' wide...a point of architectural interest that will be corrected before applying the metal. The sheathing is currently covered entirely with Grace Ice & Water shield. Question 1: Are there benefits to running purlins on top of my sheathing/underlayment to attach the metal to instead of directly through the sheathing/rafters? Question 2: The connection to the existing shingle roof will not be much of a transition (4/12 to 1/12) of pitch. What are best practices for flashing or ensuring that is as strong a component as possible in the roof system? The local Metal Depot guys are thinking a continuous sheet of flat roll flashing instead of anything with a break due to the minimal transition and the ability of flat flashing to bend as needed. Thoughts? Question 3: Insulation...patio covers are notoriously oven-like in south Louisiana and I'd like to eliminate as much of that as possible. The rafters are 2 x 6. I was originally thinking I'd put foil lined foam in the rafter spacing with a vented air space between them and the roof deck (the underside of the patio cover will be 1 x 8 ship lap, so the foam could easily sit on that). I'm unclear if that would be a good idea or a waste or if there is a better way to provide some heat relief for patio occupants. Any thoughts or ideas? I'll try to upload pictures later..until then any help is much appreciated!
Info @windowsonwashington.net
An informed customer is our best customer.
1/11/2017
1. Not unless you are trying to create some sort of vent space. This is assuming that the deck is straight the framing adequate. 2. You can run flat stock and hand bend some raised section to account for the raised parts of the panel or flatten the panel slightly. 3. Here is where your purlin and above deck venting idea might come in handy. Main roof vented? Have you seen some the DCI above deck venting products? You could make a bit of an above deck vent space to convection cool the roof and decking below. That with some foil faced foam and you would keep a massive amount of heat out of the space and then you just have to deal with the ambient oppressive Louisiana heat!!!
Kyle Finke
1/11/2017
Thanks Eric, I appreciate the quick reply. For 1: The 'point of architectural interest' is a slight trapezoid shape. The top of the roof deck is about 1" wider than the bottom. I think there is a relatively simple correction that involves trimming the sheathing. If not, could the purlins simply be the answer? For 3: The main roof is vented at the soffit and ridge. So with a DCI application air can convect from the eave to the patio/main roof connection and into the attic space? I'm taking this would be significantly more effective than the foil faced foam? If I chose not to do the above deck vent, is the foil faced foam the best bet for insulating the cover? As for ambient heat...you can't really get around that here! I do have some 72" fans in the design to assist...but on the bad days they'll just move the heat around!
Info @windowsonwashington.net
An informed customer is our best customer.
1/13/2017
1. Should be an easy "fix" or adjustment. 2. Convection will definitely cool the roof off a good bit and if you can provide for continuous ventilation (top to bottom), that should keep the air moving and the backside of the roof cooler. Foil foam is fine, but it needs and air space to take advantage of the radiant barrier benefit. I have been through LA on a couple of occasions in the summer. No mistaking that you have some decent heat in that season.
Kyle Finke
1/19/2017
Thanks again for the help. Just to clarify, I've mocked up something using my rudimentary skills in graphics. Question: is there a need for two layers/pieces of flashing and/or should the ice & water shield extend up the roof deck?
Info @windowsonwashington.net
An informed customer is our best customer.
1/20/2017
Don't need that many layers. Pull the last two courses of shingles, get you ice/water to be continuous, lap your metal up the slope, underlayment, then shingles. Should be fine.
Kyle Finke
1/21/2017
Okay...I think I got it. From the lowest layer up: Roof Deck -->Ice/water extends up the original roof-->metal flashing extends up under felt and shingles and down over the new metal roof Thanks again.

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.