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TOPIC: Roofing over existing roof

METAL OVER SHINGLES

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I AM GOING TO PUT SOME RESIDENTIAL 5 RIB 3FT WIDE WITH THE RIBS 9 IN APART. I AM GOING TO PUT DOWN 30 LB FELT ON TOP OF MY 6 YR OLD DIMENSIONAL SHINGLES AND SCREW IT DOWN. WHAT ARE THE PROS AND CONS OF THIS APPLICATION? I GUESS I MEAN OF PUTTING IT ON TOP OF THE SHINGLES.
Guest User

11/1/2004
First I would ensurev that the material you have chosen is residential grade material in that it has a minimum G90 or AZ50 metalic substrate and that it has a PVDF (Kynar 500, Hyplar 5000), SMP (Siliconized Modified Polyester) paint finish and if bare metal it should be an AZ55 substrate. Next is that your shingles only lasted 5 years so I would investigate why they failed so quickly. Usually, it is lack of or improper ventilation. The code has certain requirements so make sure you follow them. As to the application, I would first contact the manufacturer and get their recommendations. As it is residential they should have a product approval report which means it has been tested and approved by the building codes to meet your specific application as to fire, wind and rain. Most specifically the code calls for a moisture barrier under the roof covering. When you put flat steel over existing asphalt shingles it could telegraph throough if the substrate is too rough and there is walking on it etc. The heavier and harder the steel, the less chance of it. Felt underlayment helps but again contact the manufacturer.
Allan Reid
Dura-Loc Roofing Systems, Inc.

11/2/2004
THE REASON MY SHINGLES ONLY LASTED 6 YRS IS THE SAME REASON A LOTS OF US HAD IN SW FL. ON FRI. AUG 13 IT WAS CALLED CHARLIE. MY MANUAFTOR SAID TO PUT 1X4 DOWN SCREWED TO THE TRUSES NO FELT NEED AND SCREW THE METAL TO THE 1X4. I KNOW YOU PLAY IT SAFE AND SAY GO BUY THE MANF. SPECTS WHAT IS YOUR APION OF THIS AP ?
Guest User

11/3/2004
What about putting metal over shinges with 1/2 foam board underneath, any oppinions?
Guest User

11/3/2004
Not that I am a supporter of asphalt shingles however roofers tend to install them at maximum exposure with minimum nails. My first house built in 1978 still has the original shingle on it as I cut the exposure back 20% and ensured I had the maximum amount of fasteners in the right place. I guess it comes with the disposable mindset. If the manufacturer says it is approved to install this way then get it in writing and ask to see the warranty. Again I would ask to see their wind test report or product approval as you are relying on the screws to the 1x4 and the nails from the 1 x 4 to the rafters to hold the roof on. Our sytem was apprved with 2x2 and I supervised the tests where 2 - 16 d nails connected it to the rafter failed as they used the wrong type nail. I would hate to have you communicate after another hurricane that your metal roof blew off. We tested our roofs, supply certain size screws and have a FL product approval report on how to attach it. We had no failures in FL, Jamaica or the Bahamas. It is just doing right and doing it once.
Allan Reid
Dura-Loc Roofing Systems, Inc.

11/4/2004
I would need to know what type of metal you are talking about, over what type of roof assembly, in which climate and under which building code. Appreciate that you will change the properties of the product as to wind uplift, heat transfer, ventilation, moisture barrier and "FIRE". Once you choose a product, then contact the manufacturer and ask to see their product approval report. If it does not have one then be leary and contact your local building official.
Allan Reid
Dura-Loc Roofing Systems, Inc.

11/4/2004
If I get a metal roof put on over my shingled roof do I need to lay some runner strips on top of shingles for moisture barrier or can they just lay on top of shingles. I have heard some people say they need agap for this reason. Please explain further for me . Thanks
Guest User

11/11/2004
This question varies from product to product and can only be answered by the manufacturer of each individual product. There is no "rule" in regards to this. Sorry.
Guest User

11/11/2004
Guest User

11/21/2004
CAN YOU PUT METAL ROOFING OVER ASFAULT SHINGLES
Guest User

11/21/2004
Many types of residential metal roofing can be installed over asphalt shingles. This is because of the low weight and unique design of metal roofing. Each situation should be analyzed by an experienced metal roofing contractor and, if necessary, you can solicit input from the manufacturer as well. Additionally, building codes in most areas would not allow you to install over two layers of old shingles, at least not without a special waiver.
Guest User

11/21/2004
When you say it is OK to install over shingles do you mean with a, e.g., felt covering on the shingles? Otherwise I would think movement due to temperature changes would wear from the underneath.
Guest User

11/30/2004
I feel that there should always be an underlayment on top of the old shingles. Individual metal roofing manufacturers may have particular requirements in regards to underlayment. Many of the new specialty synthetic underlayments are now being used in place of felt and a slip sheet.
Guest User

11/30/2004
i install metal roofs and if you do not put felt or something over the shingles it voids the warranty of the metal
Guest User

6/3/2010