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TOPIC: Roofing over existing roof

new addition

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What is the best way to come off a existing 6/12 pitch to a 4/12 pitch and seal the overlapping joint?
Guest User

1/8/2003
I am building new 10x24 patio exposed-2x6 rafters w/ 1/2 ply wood decking this will tie into exisiting building under a 16 inch exsposed overhang via 2x6 ledger lag bolted to wall, the standard roof application in our area (Arizona) is rubber roofing (torch down) I would like info on metal roofing for low to no pitch roof (standard patio roofs here are about 1/12 pitch. What should I use for underlaymenet felt vs/ fiberglass? will this need to be vented no livable space below, just patio cover. Is there a variety of material and styles to choose from for an appilication like this? or is "tourch down" the best way to go? also is this a diy type project?
mike duquette

1/11/2003
Hi Mike, Thanks for the question. Most residential metal roofs are designed for a minimum pitch of 3:12 or sometimes 2:12. There are some interlocking aluminum-clad foam panels which can be used down to about 1:12. You have probably seen room enclosures with those type of panels. Metal roofs which are used on industrial buildings can often be used down to just 1/4:12 pitch. However, that type of system is generally not used for or available for smaller applications. It involves heavy gauge metal panels which are then mechanically seamed after installation using a special seaming machine which is brought up on to the roof. Personally, I would investigate a rubber or PVC single ply membrane roof for this sort of small nearly flat application. Todd Miller
Todd Miller
Isaiah Industries, Inc.

1/14/2003
Manufacturers recommendations for this sort of detail will vary from product to product. Generally, though, you are looking for a flashing which goes up under the higher roof by 6- 12" and then comes out on top of the lower roof by 4 - 6". The underlayment beneath all of this needs to be applied carefully to keep uphill on top of downhill. A special section of underlayment can also be brought out from the upper section back on top of the uphill flashing leg. Depending upon the roof profile, either sealant or some sort of matching profiled foam or metal closure will be used to seal off between the flashing and the lower roof panels. Todd Miller
Todd Miller
Isaiah Industries, Inc.

1/14/2003