Tips for Maintaining a Brick Chimney
Friday, March 12th, 2010
Damaged Chimney
As a homeowner, you probably check your roof (at least from the ground) after any significant storm event. However, it’s probably been a while since you inspected your chimney stack. The exterior brick portion of your chimney is exposed to hot and cold weather as well as moisture. It is common for wear and tear to take a toll. Freeze and thaw cycles can cause damage very quickly. Check your chimney every couple of years and have maintenance done before problems get out of hand.
Replace or repair metal flashing that is loose or has fallen off. Flashing keeps the seal between your chimney and the surrounding roof watertight. Preventing moisture penetration into your attic is important for reducing the incidence of mildew growth.
Install a metal chimney cap. This keeps birds and other animals from entering your chimney. It can also double as a rain cap keeping water out.
Waterproof the exterior of your chimney. A silane/siloxane sealant is ideal. It prevents liquid rainwater from penetrating into the bricks and mortar. However, it is breathable and permits water vapor to escape from the bricks.
Hire a Professional
Check the chimney crown for proper construction. Builders often cut corners when it comes to protecting the interior of your chimney from the elements. The crown should extend at least 2 inches beyond the walls of the chimney. It should be made of a precast (or metal reinforced) concrete slab - not mortar mix. The crown should slope away from the center slightly so water runs off the edges.
The flue liner extends up through this slab. It expands and contracts with the heat of the fire below. This means the crown slab should be protected from direct contact with the flue. Heat tolerant silicone caulk should be used to seal the gap between the flue liner and the crown to prevent water from seeping in.
If there are problems with the crown, chances are there is also damage to the mortar on the stack below. Get cracks and flaking repaired ASAP to prevent further deterioration.
