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TOPIC: Roofing over existing roof

METAL ROOF OVER SHINGLES

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REASONS FOR REQUIRING UNDERLAYMENT OVER SHINGLES BEFORE INSTALLING NEW METAL ROOF. I HAVE ONLY HEARD EXAMPLES SUCH AS MOISTURE BARRIER, OR AN EXTRA PROTECTIVE BARRIER OR JUST PERSONAL PREFRENCE. MOST MANUFACTUERS LEAVE THIS AS A BROAD QUESTION AND WON'T SAY EITHER WAY. OTHER THAN EXTRA INSURANCE ARE THERE ANY REASONS TO INSTALL FELT OVER SHINGLES THAT WOULD AFFECT THE QUALITY AND INTERGRITY OF THE METAL OR ITS PAINT SYSTEM??
Guest User

4/2/2008
Hello Chris, I researched several manufactuers websites and nobody will specify. I feel like you do, maybe it has just become common practice and personal prefrence. Like alot of people believe you have to add 1 x 4 purlins to provide an air space which is not a requirement neither? Felt paper or underlayment would be needed if your roof isn't installed properly and you plan to have water under the metal (opinion)(insurance). Best of luck
Guest User

4/3/2008
THANKS JOHN, MY BIGGEST CONCERN IS WILL IT IN ANY WAY AFFECT THE INTEGRITY OF THE METAL PANEL OR IT'S PAINT SYSTEM?? MAYBE TOM OR SOMEONE COULD HELP?
Guest User

4/3/2008
Chris, I have read where some think you need felt over shingles, as a contractor I don't. If your shingles are already watertight, they are also working as a vapor barrier, why would you need more? The 1x4 lathing helps on the appearance of the metal panel when you are roofing over shingles. I always beg my customers to let us tear their old roof off and start with a clean deck. The reason for this is that asphalt shingles compress. We have to achieve a certain tightness of the screws to insure that they seal. When you do this with a screw down panel the screw makes a dimple when it compress the shingles around it. When a contractor finishes the job, you can stand back and it looks like thousands of golf balls have already hit your roof. [email protected]
Guest User

4/3/2008
I suggest underlayment for these reasons: 1) To protect the building while the roof is being installed (most important for new construction obviously) 2) To keep condensation that may occur on the back of the metal roofing during certain weather conditions from affecting the old shingles. 3) If there is something about the roof installation which maybe bleeds some water during certain wind-driven rain situations, the underlayment can help avoid problems. 4) If the home should get hit by a major catastrophe (even a falling tree) and the roof be damaged, underlayment provides good protection. 5) To prevent the rough surface of the old shingles from rubbing against the back of the metal panels (this is not important when, as Wade has indicated, the metal is installed on purlins rather than dircet against the old shingles). Todd Miller
Todd Miller
Isaiah Industries, Inc.

4/5/2008
THANKS FOR THE THOUGHTS WADE AND TODD. THIS STILL LEAVES ME THAT IT IS TRULLY PERSONAL PREFRENCE, NOT MANUFACTURER RECOMENDATION!!
Guest User

4/18/2008
As a manufacturer, we always require underlayment, not because it affects our product directly but because we want property owners to have successful roof projects and we feel that underlayment is a major component of that. Todd Miller
Todd Miller
Isaiah Industries, Inc.

4/27/2008
I had my metal installed over shingles, I asked the contractor about underlayment, he stated that he had never used it in the past so my home has no underlayment with the metal directly on top of the old shingles. I have now found out that my contractor has invalid license with the state and his corparation is of suspended status. I am withholding payment from this man because I have learned that the manufacture of the metal requires underlayment. I have paid for all materails and we are only debating over the value of his labor for a job with no warrantee from a contactor who is not really a contractor and could be out of business in days much less when my problems might arrise. I will let the lawyers handle the moneies but what are some problems that I should expect from what some are now calling my temperary roof?
Guest User

11/5/2008
Gary, why don't you send me some pictures of your roof? [email protected] Todd Miller
Todd Miller
Isaiah Industries, Inc.

11/8/2008