Roof leaks occur where the roof meets the chimney and can last only one season. More tar isn’t the answer. The differing surfaces creating the roof and chimney leaks need strengthening with roofing membrane cloth.
The reason your repair does not last is that the surfaces you are trying to bond together shrink and expand differently. A simple layer of tar does not have the elasticity to bond between a wooden roof and a masonry chimney. Adding a layer of roofing membrane will give the tar strength and flexibility to last for years. Usually sold in a six-inch width, it looks like black cheesecloth on a roll.
To repair the leak, first clean any loose tar off the roof and the edge of the chimney. Then spread an even layer of tar, about three inches wide, on the roof and the side of the chimney. Apply the membrane cloth over the tar and smooth it with a trowel. Try to keep this in a straight line. Even a wide repair looks neat if the edge of the tar is uniform. Use enough tar to cover all of the membrane and your job is complete.
Membrane is also used to repair tears in the middle of a valley, flat roofs, and even leaky gutter joints.
Tip 206: Use roofing membrane whenever two dissimilar surfaces meet. It gives tar the flexibility it needs to last more than one season.
Tip 207: When doing roof repairs in damp or wet weather, use ‘wet stick’ roofing tar that adheres to a wet surface.