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I have learned a great deal reading the forum.
So far I am leaning toward a 24g 5-v gavalume roof installed on horizontal battens
over 5/8" plywood sheathing covered with composite self-adhering underlayment. Not 30lb felt. Screws, neoprene washers and caps are per manufacturer.
My question is batten strips. I understand that they cannot be treated wood. How about a material like Azek or Miratek, one of the PVC composites.
Seems the weak part of the system is the wooden batten. When the neoprene washer and fastener start to leak down the road, the roof deck is protected but not the strip securing the panel.
If not a composite, is there a better non-treated wood strip. Oak vs. pine? Other suggestions?
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It is an issue of reaction between the roofing material and the batten material. Woods have acid in them and if they become very wet the acid will leach out and attack the metal around it be it a screw or the roofing itself. hardwoods are the worse, especially oak. The air space between the roof covering and decking should be ventilated as it will then reduce heat build up and keep the moisture out of the assembly. The softwood lumber used in framing is excellant as acting as a reservoir for condensation/humidity.
If the metal roofing is coated on the back, there is less of a chance of a reaction happening. You could use metal strapping which is commonly available. Either way make sure that there are no leaks and you will be fine.
As to screws, there are various grades of screw materials, washers and rubber seals. There are stailess screws or stainless headed screws with double washers. I recommend the Atlas Ultimate screw with our through fastened product.
Don't forget you are in a high wind area. Ask to see the product approval report on the roofing material for high winds as it will dictate how to apply the roof.
12/27/2006
Dura-Loc Roofing Systems, Inc.
12/28/2006