What is waterproofing?
Bricks and mortar are porous materials and act similarly to sponges. In times of heavy and steady rains, chimneys can fill up with water that can seep into the house. This will cause structural damage to the chimney, or to the house itself. It can also lead to mold problems.
We have found that chimneys will often still leak after being properly repaired, or even after a rain cap has been installed. This is because waterproofing has not been done.
Oregon and the Pacific Northwest are some of the rainiest parts of the country. In fact, it is technically classified as a temperate rainforest. It does not take a genius to know that it rains a lot here, and the raindrops fall most of the year. In the winter, it also occasionally freezes. If you have bricks and mortar in your chimney that have not been waterproofed and then they absorb moisture from heavy rainfall, the water in the brick will freeze and expand. This will actually cause the brick or mortar to explode and result in expensive repairs.
Because of this, we use a product called Siloxane to water-seal bricks and mortar. It is a product that provides a long-lasting invisible coat to bricks and other masonry surfaces. It is applied by spraying or brushing it on until the brick and mortar start to repel the product. Siloxane allows the brick to breathe without letting water in.
In our professional opinion, waterproofing is the single most important thing you could do for your chimney.