I own a 15-year-old mobile home with a peaked metal roof. I was up on the roof recently to clean the chimney and decided to inspect the tar around all the air vents and the chimneys. It appears to be very hard and is starting to crack and flake. What do you recommend that I do to ensure that my roof does not develop leaks? (I have heard that I should replace the tar but I am not sure what with.)

Flashing details that seal penetrations through any roof are the most likely places where water can find its way into your living area. So, regardless of the type of roof you have over your abode, caulking and re-sealing the flashing details is a chore we all need to do periodically. However, there are differences between roofing on traditional “stick framed” buildings and roofing on mobile homes.

For instance, the metal on mobile home roofs have mechanically sealed seams between sheets to provide additional protection from leaks due to movement (in transit / seasonal shifting) and the low pitch design of the roof. Often, the metal is fastened to the eaves of the home, providing some structural rigidity for the exterior walls to which the roofing is fastened. These seams can lose their seals, so when you are caulking and re-sealing the other flashing details, you should consider re-sealing all these metal seams as well.

The most common material used for re-sealing flashing penetrations and metal seams on mobile homes is a silver coloured metal paint sealer that is available in 4 litre containers from your local travel trailer / camper retail sales business. However, it seems that someone has already re-sealed your penetration flashings with tar, which has now cracked and deteriorated. So, you should scrape and remove as much of this old tar as you can from around all the flashings. Then clean the metal surfaces with a petroleum distillate. If the metal is clean and free of all tar you can re-seal the flashings with the metal paint sealer. If you can’t get all the old tar off, then re-seal the flashings with a soft tar roof patching material. This product is available at any building supply and most hardware stores. If the metal roofing does not have any sheathing under it, lay a 4’ x 4” piece of plywood down in the areas where you are working so you don’t buckle the metal roofing. Because metal roofs on mobile homes are structurally rigid and flexing due to seasonal temperature changes, you should check all the seams and flashings annually and be prepared to re-seal them in spots as required. The only alternative to this regular maintenance is to consider constructing a snow roof over the length of your home.      

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This article was written by Steven Cannon, a Registered Building Official and partner in Lynch Building Inspection Services Ltd. of Nelson, British Columbia. It originally appeared in The Nelson Express.

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