With temperatures dropping significantly and snow falling across the nation, many people are rushing to get a set of snow tires and their furnaces fixed. One thing that most people don’t think about during this arctic blast is brick; however, this is a time that can be damaging to your brick if not taken care of properly. Salt can wreak havoc on your clay brick patio causing efflorescence and the possibility of shortening the life of the paving brick. Clay brick are porous and will absorb the salt along with the moisture. This salt may surface later when the brick dries causing an unsightly white residue. Also, by adding salt you may increase the amount of freeze/thaw cycles that paving brick will experience.
What exactly are freeze/thaw conditions and cycles? This cycle is the number one issue of masonry failure in Colorado. Freeze/thaw is pretty basic. Moisture freezes and then thaws. We have numerous days where the temperature drops below freezing at night and then returns to the mid 40’s the next day. Pretty harmless unless that moisture is trapped inside of something (water expands 9% when changing from a liquid to a solid). When a brick has moisture and freezes, the moisture expansion can cause microscopic cracking and lead to spawling (the brick begin to crumble or flake off). The moisture literally pushes the brick apart. When the brick get above freezing, the moisture returns to liquid again. One freeze/thaw cycle is the process of the moisture freezing and then returning to liquid one time. It is generally not an issue with Severe Weather (SW) rated brick unless the brick is completely saturated with moisture over an extended period of time. Most manufacturers in the US only make SW brick but you may find some brick that has come up from Mexico or the southern US that is only Moderate Weather (MW) rated. MW brick is not meant to be exposed to the harsh freeze/thaw cycles that we experience in most of the US. I recommend not piling a large amount of snow from your driveway on the garage’s brick and letting it slowly melt over the next few months. This will expose that brick to numerous freeze/thaw cycles and may create problems (possibly leading to a premature failure of the brick). Clay brick is excellent under compression but weak under tension (brittle).
The key is to keep the moisture out! It is probably too late to do a significant amount of maintenance as winter is here. Next spring, make sure you don’t have water entering into your building envelope, such as cracks around a chimney cap or a sill that is not shedding water correctly. Chimneys can get a significant amount of damage if they are not allowing water to drain away but instead into the system. When a fireplace or stove is used, it makes the masonry heat up. If moisture is present, it will migrate into the masonry. Once the fireplace or stove is no longer being used, it will cool down to the surrounding temperature and the moisture will freeze. If the water is not able to enter the system, no worries. If there is a lot of moisture present, the freeze/thaw cycles have just increased significantly along with the potential of the brick being damaged. Do not seal brick (unless you use a breathable sealer) as they need to be able to transfer the moisture out of a system. If any moisture is present or able to get into the system, you will trap the moisture in compounding the problem.
Water is never going to be eliminated from getting into a masonry system but you want to limit the amount entering. Also, make sure you have the proper design to allow for any moisture that does enter to exit the veneer system. If you are going to use salt on your pavers, use it sparingly and know the risks vs. benefits. With proper planning and care, your brick should last for centuries.