How to Care for the Outside of Your Chimney
A chimney can be an exposed pipe, a framed enclosure that is covered with siding (called a sided chase) that houses the flue pipe, or a masonry chimney. The chimney travels from the inside of the home to the outside either through an attic and roof or out a wall. The point where the chimney exits the structure is a primary source of leaks. Thus, you should water-test the flashing that surrounds this location using a garden hose, to make sure that it’s in good condition and leak-free.
Another potential problem area is the metal pipe itself. It can be attacked by rust, and the joints can become loose. To maintain the metal pipe,
Use a wire brush to remove the rust.
Prime and paint the rusted area with high-temperature paint.
Use a screwdriver to tighten screws at all connections.
Install new self-tapping sheet-metal screws at locations where screws were previously installed and worked loose.
Self-tapping screws are ones with their own built-in drill-bit tips. Remove an existing screw and use it as an example when purchasing replacement screws.
Masonry fireplaces have a unique flashing detail called a masonry counter flashing, which is a secondary piece of flashing that covers the primary flashing. The counter flashing has a slight lip that’s inserted into a mortar joint and then either mortared or caulked into place. Water-test the caulking or mortar annually, and repair or replace it as needed.
Apply a coat of paint to help hide otherwise unattractive flashing and prevent it from deteriorating quite so rapidly.
In areas where the climate gets unusually cold, unsealed brick on chimneys can sometimes shatter. Water enters the pores of the brick, freezes, and then expands, causing the brick to explode. You can prevent water seepage and the damage to bricks and mortar caused by freeze and thaw cycles by applying a coat of top-quality masonry sealer to all the brick or stone surrounding the fireplace and chimney. Apply the sealer with a pump garden sprayer, roller, or brush. Chimney sweeps usually keep masonry sealers in stock.