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How Wintry Weather Affects Chimneys

spalling chimney in henrico vaWhen it’s freezing cold outside, people usually know to wrap pipes and cover vulnerable plants. What many don’t realize is the potential effect the cold weather has on chimneys. Spalling and stacking are two chimney problems caused by frosty temperatures that homeowners frequently have to deal with.


The worst thing that can happen to a chimney is for excess moisture to enter the porous materials. If moisture is inside bricks, freezing and thawing cycles cause the effect of expanding and contracting. As a result, spalling occurs, which is when the front of bricks pop off or break off. The problem often begins with crumbling mortar, which exposes the masonry to moisture. A highly effective remedy is a procedure called “tuckpointing,” which involves removing old mortar and replacing it with new without having to tear down the chimney in the process. Another preventative measure is applying waterproofing treatments.

Once bricks begin spalling, a chimney rebuild is often necessary, since the bricks have been damaged and no longer properly support the structure.


Stacking is a cold weather problem with chimneys that can be complicated and a bit difficult to understand. It involves pressure in the home weighed against a column of cold air in the chimney and frigid outdoor temperatures. A simple way to put it is that the stack effect causes a building to act like a chimney. The imbalance in air pressure caused by stacking can prevent the chimney from operating properly. This means combustion gases from a fireplace will go into the home instead of up and out of the chimney.

Understanding the Stack Effect

Stacking is a winter problem that doesn’t occur in warm months. When it’s cold outside, the warm air inside your home is lighter and becomes like a bubble of air that rises and creates pressure to escape. When air flow leaves the home at the top, cold air is drawn in through cracks at the bottom. A drafty home consumes huge amounts of energy during this process.

The stack effect is continuous on cold days, and it generates tremendous pressure. In high-rise buildings, there was a time when this pressure prevented people from opening the front door in wintry weather. This is why revolving doors were invented.

The Stack Effect and Chimneys

The negative air pressure in the home caused by the stack effect can cause a chilly backdraft in a chimney that has cooler air than room temperature. This almost exclusively happens when the chimney is built on an outside wall. If you try to light a fire in these conditions, smoke will enter your home instead of exiting through the chimney. Here are some tips of most help before a home is built:

  • richmond va chimney damage and repairAvoid the problem of chimney stacking altogether by designing your home in such a way that chimneys are built in the home’s interior, not the exterior. It’s not too late, however, to add a fireplace and chimney in the interior of your existing home.
  • Make sure the design of your home allows for a straight chimney, not one with 90-degree offsets or turns, since smoke and possibly cold air can get trapped there. With a vertical, straight design, the smoke from your fireplace can exit your home through the chimney more easily.

Contact the Chimney Experts

If you want to take preventative measures to protect your chimney or if you need chimney repair or rebuild, contact the chimney professionals at Chimney Saver Solutions. They are experts in restoration of chimney stacks and in handling all chimney-related needs. Call 804-440-5000 to avoid problems of spalling and stacking in winter.

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