How to Seal Chimney Flashing

Old houses often develop cracks between the chimney and the roof. In this article, the cracks between the chimney and a metal roof are sealed using roof cement. This is a perpetual maintenance issue and should be checked every few years. Here's a list of items you will need.

Step 1:

The first step is to access the roof using an extension ladder, preferably on a warm day. If you are using roof cement, I recommend using the tube package which fits your caulking gun. The gun only requires one hand, whereas the roof cement in a can requires two hand, to hold the cement and a trowel. The cement in a can may be less expensive, but we would recommend against this, especially on a tin roof like this one.

Step 2:

First examine the area between the brick and the roofing, looking for small cracks, separations and loose areas. These are caused in part by deterioration of the old cement and the different thermal expansion properties of the chimney and the roof.

Step 3:

Using the caulking gun, force ample amounts roof cement into the cracks. Apply a liberal amount in all areas.

Step 4:

On the vertical areas it may be necessary to smooth the excess cement using a trowel.

Step 5:

After the chimney is sealed, look to the plumbing vents and don't overlook the stack of the flue