Winter is a very hard time for your brick. While you sit inside nice and warm, perhaps around a fire in the fireplace or comfortably warmed by a different heating appliance, the brick on the exterior of your home are experiencing every change in temperature, from the drops below zero to those days where the temperature can’t decide if it wants to be above or below freezing.
All of these circumstances affect your brick in that the water that is naturally found inside of them in the form of water vapor will freeze and thaw according to the temperature, causing damage to
the brick. The way that this water damages your brick is that as water freezes, unlike other elements on Earth, it expands to a larger form than in its gaseous or liquid state. Think if you put a water bottle full to the brim of water in the freezer. When you come back to it, that water bottle’s lid will likely have popped off because the volume that the ice takes up is larger than the volume that the water took up.
This principal attribute of water is the reason why so many companies have spent so much effort in creating products to protect the brick and other masonry surfaces on your home. The
cracks in which water lies or the pores inside the brick in which water vapor is found work much like the bottle in the freezer. As the water expands it needs somewhere to go so it pushes and pushes on the brick or other masonry until it has the room it needs, which often means damage to the brick.
To prevent such damage from occurring it is prudent to have applied water repellent to your brick, especially to your chimney which is subjected to more of the elements than the rest of the home. A good water repellent is deep penetrating instead of film forming. What does this mean? It means that a good water repellent is not going to merely sit on the surface of the brick you are applying it to and form a barrier, it is going to sink deep into the brick and form a semi-permeable barrier. This barrier will allow water vapors that are trapped inside the brick to be able to exit but still prevent water molecules from entering. Spalling (the faces of the brick popping off) occurs when water vapors inside the brick are trapped in. They expand and contract continuously until the front of the brick has come off to allow for this process to keep occurring.