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.
A Chimney Crown Protects your Brick Chimney
The chimney crown provides a brick or stone chimney with a sloped top surface to shed water off the top of the chimney. If the crown is porous or cracked, water can penetrate the underlying brick and mortar, causing deterioration and progressive destruction of the masonry chimney, and may also cause damage to interior finishes adjacent to the fireplace.
Porous crowns allow water to penetrate the brick and mortar joints, rather than being safely shed off down the sides of the chimney.
As illustrated here, a cracked or loose crown can lead to loose brick and deterioration of the brick and mortar joints below.
Water which pools on top or penetrates the brick structure can lead to deterioration of the underlying brick and mortar over time, causing chimneys to fall apart brick by brick.
Winter weather can speed this process as water freezes and expands, prying the bricks and mortar apart. Further deterioration can create a porous counter flashing, allowing water to get past roofing materials (more on this issue below).
A chimney shoulder is also susceptible to water infiltration and needs a crown or cap to prevent damage and decay of the brick and mortar just below it.
Here the chimney shoulder was poorly protected with an inadequate crown for drainage and the moisture penetrating the brick below has caused brick and mortar deterioration.
Beware of Crowns Built with Mortar
Deteriorated chimney crowns are quite common in Texas, because crowns are often built with mortar…the cementitious “glue” used to bond brick or stone together. Mortar is subject to cracking or deterioration when misused in such ways.
With a strength of 700 PSI, mortar is not designed for the purpose of pouring or forming a flat surface such as a chimney crown, although it is a common practice in southern states.
Mortar crowns crack and deteriorate prematurely. Instead, crowns should be built with Portland cement or concrete, which have a stronger compressive strength of 2500 PSI or more, providing a lasting capability to effectively shed water.
This cracked and porous mortar crown is allowing water to soak into brick and mortar, causing spalling and deterioration. This process of deterioration increases steadily until porous joints allow water to penetrate into the home by outflanking the counter flashings and allowing water leaks around the perimeter of the roofing materials. (See Chimney elements which can cause leaking)
This concrete crown looks similar to a new mortar crown, gently sloping to shed water away from the top of the chimney. (Note that the metal cap shown also prevents rainwater from entering the chimney flue, which can cause damage to interior chimney components.)
Crowns are Often Formed with Mortar
As a simple matter of convenience during initial construction, mortar is conveniently available on the roof already as the brick chimney is being laid. So rather than mixing and finishing a crown with concrete (which, with stone aggregate included, is also more difficult to form into a smooth finish) many contractors simply use the available mortar to create a “quick and easy” crown.
Such inferior mortar crowns may last several years unnoticed, until water has infiltrated the chimney and caused damage.
Chimneys Often “Out-of-Sight, Out-of-Mind”
Penetrating water may also eventually affect the chimney flashing. Defective chimney flashing may also allow water into the house, causing stains, damage to wood floors, or other interior finishes…so obviously it’s important to ensure that the chimney components are properly shedding water, just as well as your roof.
Can We Help You with an Issue with Your Chimney Crown?
Over the years, Brick Doctor has done just about everything when it comes to repairing and restoring crowns on brick chimneys. We know what we are doing. Let us know if we can help you.
Don’t take our word for it. (Check out our reviews). And, even better, ask a neighbor for a recommendation. We have done tens of thousands of projects all over the DFW Metroplex since 1986, including for some of your neighbors.
Have any particular questions or concerns about your chimney crown at your home? We can help.
Brick Doctor is always ready to answer your questions, address your concerns or provide an estimate for repairs designed for the scope of your needs.
We look forward to assisting you. Reach out today. Contact us