Roofing/Roofing repair

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Question
I have a 120 y/o home in central Pennsylvania.  The porch roofs are very low slope standing seam tin with built in gutters.  The previous owner coated the surface with hot tar.  Although the majority of the surface is in good condition, there are areas that need to be recoated.  Hot tar roofing contractors are difficult to find these days so I am wondering if there is a product that can be applied to the surface that will adhere to the exisitng surface?  If so, what is it and how difficult is it to apply?  Thank you for thaking the time to respond to this question.

Answer
Mr. Bates,

In review of your question, I will make a couple presumptions, the low-sloped porch roof you speak of was actually covered with hot asphalt.  The only "tar" we use in the roofing industry is Coal Tar which is rare (at least in the past 10 years) due to its health concerns related to fumes during installation/handling.

You did not mention if the metal panel was a flat panel or has raised laps.  If it is older it could be either type. Regardless of metal type, if they simply took hot asphalt and flood coated the metal panel roof and it is not cracking and crazing badly, resurfacing could be an option.  Your only viable option is to wash the roof of surface contaminates and coat using a water-based asphalt emulsion. If reinforcement is needed, the initial 4 gallon per 100 sq ft of emulsion should have a 40" wide piece of stitchbond polyester laid into the wet emulsion and back-rolled with an emulsion wet roller, this will wet the fabric into the base layer of emulsion.  Allow to dry 24 hours and apply a second layer of emulsion at a similar rate of 4 gallons per 100 sq ft.  The finished emulsion surface can be recoated over the years as needed with a mild cleaning. The application of elastomeric acrylic coatings can be applied atop the cured emulsion (wait 7 days to cure) if you wish the have a more reflective surface.

Being the existing surface is contaminated with an asphalt product, the use of emulsion as the coating material is best.  Even if the surface is an older coal tar, the emulsion will still work pretty well, just not likely to last as long between recoating.  Hopefully this will provide you some insight as to what you should have and a decent way to work with it.

Steven C. Wadding RRC,RRO,CDT

Roofing

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Steven C. Wadding RRC,RRO,CDT

Expertise

General questions in regards to most roof types and situations. As the Technical Services Manager for Polyglass USA, Inc. this would not be a forum to address any issues directly related to a product my employer manufacturers.

Experience

I have been active in the roofing and waterproofing industries for more than 30 years with extensive experience from product installation, product development and consulting. I have been active in the Construction Specifications Institute and Roof Consultants Institute for approximately 20 years. I am a member of ASTM and am a voting member of various subcommittees. I have many years of consulting experience in the fields of Roofing, Waterproofing and Exterior Building Envelope disciplines.

Organizations
Roof Consultants Institute Construction Specifications Institute ASTM

Publications
Division 7 Technical Binders for Malarkey Roofing Products and Polyglass USA, Inc. CSI Phoenix Chapter Cactus Comments

Education/Credentials
Registered Roof Consultant - Roof Consultants Institute Registered Roof Observer - Roof Consultants Institute Certifified Document Technologist - Construction Specifications Institute Spray Fireproofing Special Inspector - International Code Council

Awards and Honors
Registered Roof Consultant - Roof Consultants Institute Registered Roof Observer - Roof Consultants Institute Certifified Document Technologist - Construction Specifications Institute Spray Fireproofing Special Inspector - International Code Council

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