Join the MRA | Member Login
Find a Professional
Sign Up Log In Add New Topic

TOPIC: Galvalume

Asphalt paper

Return to Galvalume

Return to Archive

Return to Forum

What are the negatives for using the black tar-like paper under a galvanized roof sheet?
Guest User

6/19/2002
It is a requirement of the residential steep slope building codes that an underlayment be used under the roofing material unless you have your material tested otherwise. The purpose of the underlayment is generally two fold in that it can act as a secondary membrane in case of severe weather like ice damming or torrential wind driven rain and secondly as a condensation barrier. The product should allow air to pass through while trapping any moisture and shedding it down and off the roof. There are various types but the most common and economical is a asphalt impregnated felt paper and the code in the US requires 0ne layer of #30 or two layers of #15. This product is typically laid loose although for best protection in severe weather climates, it should be cemented together from the eaves up to a point 3 feet inside the exterior wall. When installing a metal product over a solid sheathing or existing roofing materials, the felt underlayment acts as an ideal separator to stop any telegraphing of imperfections up through the metal much like a carpet underpad. Please be aware that the fely is a paper manufactured from a wood product and depending on the application, the asphalt may break down over time. There are many other upgrade underlayments available. Good Luck.
Allan Reid
Dura-Loc Roofing Systems, Inc.

6/20/2002
Guest User

12/18/2002
I had a standing seam metal roof put on my new screen porch at the beginning to this year. Our house is in North Georgia and we get gusting winds and rains and pretty cold temps. My contractor put down a layer of plywood or obs, then a layer of foam, then the metal panels. Should he have put down felt also? I am getting some bad leaks, especially at the top of the roof where it meets the existing house, and I was thinking there was a problem with the flashing. Any suggestions and advise would be greatly apreciated. Thank you, s henderson
Guest User

12/27/2002
Assuming that the screened porch is open to the environment I question why the insulation was put down? Anyways it does not sound like you have a condensation problem, but more like a workmanship issue. Depending on the roof slope and how he connected into your exist house will dictate the type of problems. If it connects into the side of your home with no roof area above exiting on your porch roof, it could be the flashing connection to the wall where the water is getting behind the upper termination of the flashing. If it connects into the fascia of an upper roof with water shedding onto the low slope porch roof it could be that the wind is driving and syphoning the rain up under the flashing over the SS sheets. Ensure that he used a self adhesive foam closure strip over the SS sheets and under the flashing. If this is not the cause get back to us with more information. Hope this helps.
Allan Reid
Dura-Loc Roofing Systems, Inc.

12/27/2002