Brick chimneys are vulnerable to harsh weather elements and are fully exposed to rain, freeze/thaw cycles, and lightning, yet they are often out of sight and out of mind. This situation offers opportunity for problems to develop unnoticed. Loose bricks on your chimney or brick shards found on the roof, gutters, or flower beds are indicators of potential leaks. Any of these conditions warrant an inspection by a masonry repair expert. Roofing experts also often notice such potential problems and may recommend the chimney flashing be inspected and/or repaired by a repair mason.
The sooner any masonry chimney problems are addressed, potentially the less expensive the repair. Brick Doctor can often help prevent or minimize many masonry chimney problems, whether it’s brick, stone, mortar, flashing, crowns, or chimney caps.
Many brick defects can appear quite subtle and still create leaking problems around chimney counter flashing. Brick fragments at the base of this chimney indicate water penetration and freezing of the brick, which pops off layers or pieces of the brick (spalling).
While many chimneys are “out of sight, out of mind,” even a cursory view from the ground may often indicate brick or mortar damage caused by a faulty chimney crown. Brick Chimney problems often start with a problem with the crown and then as water infiltrates, other issues arise…loose or spalling brick, and deteriorated mortar. Antique or other porous-types of brick are particularly vulnerable, and may need periodic waterproofing to help prevent damage.
First, it’s important to consider chimney flashing along with the entire brick chimney and the roofing assembly, realizing that all components must be sound to prevent water from entering your home. Problems with chimney flashings are a common cause of leaks. Determining whether you have a roofing problem, or a masonry chimney or flashing problem, may require expert advice or even leak testing. Although we are not leak detection experts, we can diagnose any visible masonry problems which could be causing damage from water infiltration. Chimney components which can create leaks are discussed here.
The image below illustrates the relationship between the counter flashing and step flashing, which are a component of the primary flashing assembly installed by the roofer. Roofing materials and chimney components depend on each other to prevent leaks. Porous brick above and around the counter flashing can allow water–which should be shedding off, down the masonry chimney–to enter your home’s interior through the brick.
This is a schematic for a composition shingle roof or any flat dimension roofing material. Tile of any kind or metal would be configured differently to accommodate the dimensions of the roofing material.
The diagram shows roofing materials–shingles and underlayment, with the primary flashing–in this case, the step flashing, which is layered in with each row of shingles. The counter flashing embedded in the brick provides water shedding cover on a brick chimney. (Photo- courtesy of National Roofing Contractors Association.)
The counter flashing is either cut continuously into the brick face or embedded into the mortar between bricks. The counter flashing extends from between layers of bricks and bends down, overlapping the top of the primary (step) flashing. Water sheds from the brick chimney surfaces down the outside of the step flashing.
Many brick defects can appear quite subtle and still create leaking problems around chimney counter flashing. Brick fragments at the base of this chimney indicate entry of water and freezing of the brick and mortar (spalling).
Here is an original counter flashing installed when the original masonry chimney was built. The brick and mortar above has been repaired and this chimney flashing is shedding water properly.
Let’s explore deteriorated brick chimney flashing issues further.
An up-close view of a porosity problem. This chimney has been subjected to poor repairs, with both mortar and caulk squirted into a joint, without tooling. Just above that, an open void exists which could allow water penetration as well. Unprofessional repairs also indicate that a previous problem existed.
Any cracks in the face of the chimney masonry can allow water entry because invasive water can outflank the counter flashing and enter your living space. This is a “before” picture of the image above, before the repairs were made.
When flashing materials are working properly and the bricks and mortar are sound, a chimney is watertight. However, even a minor breach in the chimney brick or the counter flashing can cause a significant leak, as water which should be shedding over the counter flashing, is instead outflanking and getting behind the step flashing. This water can then pour into your home’s interior, potentially damaging wood, drywall, and flooring materials, or cause mold to grow.
Roofing Issues
Even the soundest of chimneys will not stop leaks if the leak is caused by defects or faults in the roofing assembly, including the primary flashing assembly. The most critical part of the primary flashing is the head flashing up slope from the chimney, which must divert water from the slope around the chimney and ensure water sheds properly around the sloped sides of the chimney. The primary head flashing diverts water onto and over the step flashing assembly described above.
In Texas, chimneys wider than 30″ require a cricket upslope, as more water must be diverted over a longer area. Flat metal technology is cheaper; but not as fundamentally sound. Several other problems can exist on on particularly wider chimneys. Windblown leaves and other debris can accumulate behind the chimney, which can cause water damming and exacerbate these problems.
The chimney cricket adds slope around the chimney and is a preferred technology to the flat head flashing.
The chimney cricket adds slope around the chimney and is a preferred technology to the flat head flashing. This is the best design for shedding water and preventing debris build-up, but more expensive to build.
Poor craftsmanship, both the flashing assembly and the haphazard placement of bricks, dictate that extensive repairs are needed.
This head flashing on a brick chimney situated on a rake edge is not properly diverting water to the inside and down the roof but letting at least some water run off on the wood rake edge, causing deterioration of the trim. These problems are caused by the original roofer. This chimney also needs some mortar repairs.
Competent masonry professionals can eliminate the masonry chimney as a possible source of water leaks.
Brick problems can be subtle. Disbonded mortar and brick can allow water to wick between brick and mortar, but this leaves clues which an expert masonry repair specialist can observe and diagnose. Poor bonding between counter flashing and brick and mortar can also allow moisture to get past the counter flashing. Masonry experts familiar with these issues should be able to spot this problem and explain a proposed solution. For more answers on how chimneys can leak, click here.