Repair or Replace a Damaged Chimney Crown
The chimney crown (also referred to as the chimney wash) is the top element of a masonry chimney. It covers and seals the top of the chimney from the flue liner(s) to the chimney edge. Most masonry chimneys are built with an inadequate crown constructed from common mortar mix, the same mixture used to lay the bricks of the chimney. This mortar is not designed for and will not withstand years of weather abuse without cracking, chipping or deteriorating - situations that allow to penetrate the chimney. In fact, most sand and mortar crowns crack almost immediately after installation because of shrinkage.
A proper chimney crown should be constructed of a portland cement-based mixture and cast or formed so it provides an overhand, or drip edge, projecting beyond all sides of the chimney by a minimum of two inches. The flue liner tile(s) should project above the crown a minimum of two inches.
The crown should provide a downward slope that will direct the water from the flue to the edge of the crown. The overhanging drip edge, by directing the run-off from the crown away from the chimney, helps prevent erosion of the brick and mortar in the chimney's vertical surfaces.
Repair Deteriorated Mortar Joints
Deteriorated mortar joints are entry spots for water. Proper mortar joints have no gaps or missing mortar and are struck, or shaped, in a way that directs water out of the joint.
When mortar deteriorates from exposure to weather, it becomes much more absorbent. A common repair for improper or deteriorated mortar joints is called rejointing or tuckpointing. In this process, the existing mortar joint is cut out to an appropriate depth and the joint is repacked with new mortar compound. The joint then is struck to form a concave surface that will direct water out of the joint. A good repointing job, using proper materials, will give the chimney a much longer life span, and often will enhance its appearance.
Repair or Replace Flashing
Flashing is the seal between the roofing material and the chimney. Flashing prevents rainwater or snow melt from running down the chimney into living spaces where it can stain or damage ceiling and walls or wall paneling or cause rot in rafters, joists or other structural elements. In many cases, the flashing is a single L-shaped sheet of metal that is attached to the side of the chimney and the roof. The most effective flashing is made up of two elements, the flashing and the counter-flashing. The flashing or base flashing - an L-shaped element extending up the chimney side and out onto the roof - is attached to the roof and sealed. The counter flashing, which overlaps the base flashing, is imbedded and sealed in the chimney's masonry joints. This two-element flashing allows both the roof and the chimney to expand or contract at their own rates without breaking the waterproof seal in either area.
Install a cricket to stop or prevent leaks If the chimney is located on the low side of the roof, where the flow of run-off is directed against the chimney, the installation of a cricket will afford additional protection against water leaking into the home. A cricket is a water deflector that serves to direct rainwater away from the chimney. Crickets are recommended on chimneys more than 3D-incheswide and they are especially important on steep roofs.
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