Maintenance and repair of brick and mortar above the roof line are essential for a roof system to function properly. Many roof Leaks occur near the chimney and can usually be attributed to defective flashings, cracks or deterioration in the chimney cap, or problems in the mortar joints of the chimney. For more information on chimney flashings, click here.
Masonry Repairs at Chimneys
It’s important to understand the various components of a masonry chimney, especially when determining the source of a roof leak. The bricks at the chimney should extend a minimum of 3 feet above the roof line at the base of the chimney. Each course of brick is bound with mortar to ensure the chimney is watertight and to uniformly distribute the weight load of the chimney. Flue liners are typically installed in chimneys to prevent heat transfer to combustible materials and prevent gases from penetrating the living space. A mortar cap or chimney crown protects the other components of a masonry chimney from the weather. Lastly, chimney flashings are embedded into the mortar and ensure that the roof is watertight at the transition between the roofing materials and the masonry system.
Common masonry repairs at chimneys are as follows:
- Brick Replacement – Bricks can become damaged and need to be replaced. This usually occurs from water infiltration from the top of the chimney and worsens when the moisture is exposed to a freeze-thaw cycle. This cycle will cause bricks to deface and become brittle in nature. The best practice for brick replacement includes removing the brick and cleaning the area with a wire brush to allow new mortar to bond properly. A new brick and new mortar joints should then be installed. If a semi-permeable masonry sealant is needed, the mortar should set for fourteen days before application. Maintaining brick is vital to ensuring the longevity of the chimney. If neglected, extensive damage to the bricks can cause the need for the chimney to be rebuilt.
- Tuck Pointing – Water can easily enter a house or building through deteriorated mortar joints, especially during heavy wind-driven rains. In order to effectively tuck point a chimney, all bad mortar should be removed with an electric grinder. Using a tuck pointing tool and mortar mix, the new mortar should be applied to clean brick in order for the joint to properly bond. Again, it is important to allow new mortar to set for fourteen days before applying water repellant.
- Chimney Reconstruction – If damage to a brick chimney is found and the extent of the damage is deemed unrepairable, rebuilding the chimney is a viable repair option. This process starts by removing all bricks, mortar joints and flashings from the top of the chimney down to the areas that have not been affected by the damage. The most common areas that are unaffected by damage are beneath the roofline as they are less subjected to the elements of weather. After the majority of the exterior structure of the chimney has been removed, the clay flue liner(s) need to be inspected for damage. At this time, if necessary, the flue liner(s) would be replaced and would be set onto one another embedded in a fire and heat resistant mortar. Installing new brick will then commence. The chimney will need to be reconstructed using a style of brick that most resembles the brick being removed. These bricks will be set into a Type-S mortar mix and will need to be installed evenly both horizontally and vertically. This reconstruction will continue to the original chimney height or the appropriate height in accordance with building codes and fire safety regulations. red in inches. Common thicknesses of aluminum (from thinnest to thickest) include .019, .024, .027, and .032.
- Cast in Place Chimney Crown – Cracks in chimney crowns cause damage to bricks and the interior of the house or building. Repairs to chimney crowns are rarely effective and should be considered temporary in nature. The old crown should be removed and replaced when cracks appear. At this time, the flue liner should be inspected for cracks or damage as well. To have a lasting crown, a barrier needs to be installed around each flue(s) and on the brick/filler that forms the top of the chimney. This will keep the concrete crown from bonding to the bricks or the flue(s). If allowed to bond to these components, cracking is likely to occur due to the expansion and contraction of the chimney, flue(s), and crown. When properly installed, the concrete crown should be able to float and expansion and contraction will not damage it. The crown should be installed with a two inch over hang and a drip edge underneath to prevent water from rolling down the brick. The concrete should be highest at the middle, then tapered to the edge of the form to prevent water from pooling on the crown. After the concrete has set, a masonry caulk is applied at the flue to make the moisture barrier water tight. Metal flue caps can be added to prevent water from entering the flue(s).
- Chase Covers – Chase covers serve the same purpose as a masonry crown but are fabricated from metal. Chase covers are not commonly found over brick chimneys and are more common on wood framed chimneys. All chase covers need to be tapered to allow proper water runoff. A drip edge must be fabricated to allow water to drip away from the chimney. A collar, or flange at the flue penetration should be a minimum of 1-2” in height. Copper and stainless steel are naturally weathering metals and require very little maintenance. Galvanized steel chase covers can be used as long as they are properly painted and maintained. Fasteners should not be installed on the top of the chase cover, and instead the fasteners should penetrate on the sides to prevent water infiltration.
- Chimney Flashings – Failures caused at chimney flashings are common as many contractors do not replace them at the time of a new roof installation. Flashings should always be replaced when a new roof is installed as it is much more expensive to do it at a later time as a repair. For more information about chimney flashings, click here.
Please do not hesitate to contact us for more information on pre-manufactured steel roofs or metal roof repairs.