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Roofing/Replacing a Front Porch Roof on a Row Home

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Question
My row home's front porch roof is in need of repair/replacement. There doesn't appear to be any sort of divider between my roof and the neighbors' roofs on either side.  They are all currently "torched" roofs with 2-4 layers of material.  I have proposals from two respected roofing companies to replace my roof with EPDM.  One company says the adhesive used for EPDM is incompatible with a torched roof and the other says its fine.  The one who says its incompatible will essentially install a piece of metal flashing where the EPDM meets the torched roof to "marry" the two.  The other company will overlap the EPDM over to each of the neighbor's roofs.  Is one right and one wrong or is it a "style" thing?

Answer
Cured EPDM (rubber) and modified asphalt membranes are incompatible. If your membrane has granules it could be either APP (plastic modified) or SBS (rubber modified). If it has no granules and is black, it is APP.

So I assume you are replacing your roof and your neighbor is not. So how does one tie-in an asphalt modified membrane to an EPDM roof.

The metal tie-in is a good idea since it can be married to both membranes.
Tie the metal into your roof with the EPDM bonded to the sheet metal. If fact ask your roofer if you could use a seam tape adhered with primer to the metal, then bond the EPDM to the seam tape, just like completing a standard EPDM sidelap. Extended the primer past the outside edge of the seam tape so it will help the lap sealant adhere to the metal when you install it at the leading edge (end of the EPDM membrane on the metal)over the seam tape.

The modified membrane would have to be torch-applied to the asphalt primed other half of the sheet metal. The leading edge should be sealed with asphalt mastic

Hope this helps.

Roofing

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D. John Henderson

Expertise

My 33 years in the building science business has involved air barriers, waterproofing, and flat & steep slope roofing systems.

Experience

My roofing encompasses commercial systems (BUR, mod-bit, single-ply) and residential applications (asphalt shingles, cedar shingles, slate and metal. I am cognizant of code stipulations in regards to FM and UL for commercial roofs.

Education/Credentials
Attended numerous courses offerd by Roof Consultants Institute, Roofing Industry Educational Institute, Factory Mutual Research Corporation, University of Wisconsin, and BURSI. Lectured for RCI and mentored at a local university for a Building Science Certificate.

Past/Present Clients
Government, commercial businesses such as The GAP, hospitals, school boards as a roof designer.

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