How to Seal a Chimney

Sealing a chimney is important to fix cracks and leaks in the chimney. If there are cracks or leaks it can be messy and wet inside your home come rainy season. It is also important to seal your chimney so that it works properly and smoke does not escape through the cracks or leaks.

Instructions

1. Determine which type of seal you would like to use. You can use roof tar and spread them over the cracks or leaks but flashing is the best method to use.

2. Install flashing onto the cracks in your chimney. Flashing is lightweight and thin pieces of aluminum or galvanized metal that you will use to seal your chimney.

3. Bend the flashing into an "L" shape with the upper part of the flashing flush against the chimney and the lower part of the flashing resting on the shingles on the roof.

4. Install the flashing beginning at the bottom or lower part of the chimney and working toward the top of the chimney in a stepped fashion.

5. Fasten or nail the flashing to the roof but not directly onto the chimney.

6. Install a piece of counter flashing over the flashing and fasten it directly onto the chimney. To do this cut a groove in the covering of the chimney and bend a small lip on the counter flashing.

7. Place the lip inside the groove and seal it in place. Now when the roof moves because of wind the tow pieces of the metal flashing will slide against one another preventing bending and damage to the flashing.

Tips & Warnings

• To bend the flashing you may need the assistance of either a sheet metal worker such as an HVAC, or heating venting and air conditioning contractor to bend the metal. If you have metal bending tools you can do this yourself.

• If the crack is very big on your chimney you may want to consult a professional because you may need to fully replace it or have major repair work done on it.

• Considering you may be working on the roof wear shoes with good traction so you do not slip. It also will be a good idea to use a roof harness when you are working on your roof.