Where to install spark arrestors – The definitive guide for homeowners
Spark arrestor were originally used to keep coal or wood burning stoves or fireplace sparks from floating or flying out of the chimney and inciting fires at other adjacent or nearby building components.
The image below shows an example of where someone installed a bit of hardware fabric to function as a spark arrestor. Although this is better than nothing, this chimney top is missing a rain cap. Rain caps are necessary to keep the majority of precipitation out if the chimney. In cases like the inage below, where there is no rain cap, as significant amount of precipitation will get into the chimney everytime rains.
That rain water will enter the joints of the terra cotta flues and cause damage and deterioration over time. Rain can deteriorate cavities and partially concealed locations, such as chimney shafts, at accelerated rates.
In the image below you can see an example of a terracotta flue with no spark arrestor and not even a cap. This condition is prolific around Washington DC and Capitol hill historic buildings, but it’s a problem that should be fixed. The spark arrestor would keep rodents out. Squirrels are invasive and birds like to look for places to live inside of chimney’s.
Also as mentioned above without a cap, heavy rains will just wash directly into the chimney and dry out excessively slowly. The moisture will infiltrate masonry materials and disolve binder salts and cause swelling and delamination of adhered or attached materials.
The photo below shows an example of a historic brick chimney with cap and spark arrestor in place.
