What Happens When Water Freezes and Thaws in Your Chimney?
Winters in the Pittsburgh, PA, region are brutal, and no one who lives here needs to be told that. What some homeowners aren’t aware of, however, is the damaging effect that freezing and thawing water from rain and snow can have on their chimneys.
It’s called the “freeze-thaw cycle,” and Advance Chimney Sweeps would like to tell you how it happens, what to do about it, and how to help prevent it.
Water vs. chimney bricks
When it comes to the never-ending battle between rain and chimney bricks, the rain always wins out over time. Bricks are porous and allow small amounts of water to move into them. If you see white staining, or “efflorescence,” on your chimney’s exterior, it’s because water is intruding and leaching out the naturally occurring salts inside the bricks.
Cracked bricks let in more water, and this is when the real trouble starts.
What is the freeze-thaw cycle?
It starts when water freezes and then expands, pushing against whatever is around it. In the case of your chimney’s bricks, something has to give, and it’s usually not going to be the expanding ice!
With the first freeze, ice may cause minor brick damage. With subsequent freezes and new intrusions of water, greater damage will occur. Water begins to freeze whenever the mercury dips below 32 degrees, and it starts thawing when temperatures rise above that. This cycle can happen repeatedly during a typical Pennsylvania winter.
Freeze-thaw cycle chimney damage
Masonry damage from freeze-thaw cycles can include:
- Bricks with small or large cracks
- Gaps between the bricks and mortar
- Spalling (flaking) brick faces
- Missing sections of mortar
- Missing bricks
- A chimney that leans
- A chimney that collapses
How to address damaged chimney bricks
You can’t keep outside temperatures from fluctuating, and you can’t prevent occasional cracks in your chimney bricks, but you can repair a chimney that’s been damaged by freeze-thaw cycles. And you can take steps to keep the damage from recurring.
Chimney inspection
All chimney repair work should begin with an inspection performed by a qualified chimney technician. The inspection will tell you and the inspector the type and extent of the freeze-thaw-cycle damage. It will also tell the inspector how to fix it.
Brick replacement
This is often enough to solve most minor and some moderate masonry damage.
Tuckpointing
If mortar is missing or crumbling between the chimney’s bricks, it can be replaced through a process called tuckpointing.
Flashing replacement
The flashing that seals that gap between your roof and chimney can become dislodged, rusted, or warped, and needs to be replaced. This material protects the chimney below the roof (and parts of the home) from water damage.
Chimney crown rebuilding
A cracked concrete chimney crown can put the bricks beneath it at risk of water damage. Damaged crowns can be patched, sealed, and rebuilt.
Partial or complete chimney rebuilding
Large sections of damaged chimney bricks can be rebuilt. The entire chimney can be rebuilt if freezing and thawing have caused widespread damage.
Chimney waterproofing
When all necessary repair work is completed, the chimney can be waterproofed with a strong, vapor-permeable sealant to prevent future water intrusion.
Call for help with your damaged chimney
Advance Chimney Sweeps is ready to help with all your chimney needs. We provide complete repairs, rebuilding, inspections, and chimney sweeping. Reach us by phone in the Pittsburgh, PA, area, or use our contact form.
