What you need to know about the freeze thaw cycle.
A common problem in our area is what’s known as the freeze-thaw cycle. Not an exciting blog topic, but a very important one. Here I will discuss where and how it happens, the potential damages it can cause, how to identify it, what to do if you have it, and a few tips on how to prevent it in the future.
Masonry veneers, whether they are brick, block or stone, are porous, meaning they absorb moisture. In certain situations the moisture will remain in the wall and freeze. When water freezes it expands, opening up a larger area for the water to accumulate the next time, and so on and so forth, until it expands to the point it pops the face off of the material. Popping the face off the material is commonly referred to as spalling.
Examples of spalling masonry:
That, in a nutshell, is a quick, nonscientific overview of the freeze thaw cycle. Now, we go in deeper. Moisture is everywhere around a house. There are the obvious sources of moisture against masonry such as rain and snow, and watering your lawn and flower beds, then there’s the one that no one thinks about, humidity. One of the reasons the humidity is more of a problem here than other places is the major temperature swings we have. In the afternoon one day it can be 75 degrees with a dew point of 60, and by the next morning it will be 20 degrees. That rapid of a temperature change doesn’t allow the moisture enough time to dissipate out of the masonry. In most cases none of these are serious issues. But, handled improperly, they can lead to serious and expensive issues.
Another factor in spalling of masonry is the material itself. The softer limestone used predominantly around here is quarried in southern Kansas, typically in Silverdale or Winfield. Those are the yellow to goldish colored stones used all throughout our area. They are soft, and extremely porous. They are very susceptible to the freeze thaw cycle.
Whereas an Arkansas ledge stone, the second most popular stone in our area, is hard and not nearly as porous, therefore not as likely to be damaged. They are the brown, tan to orange & peachish colored stones.
Brick are more complicated, there are no easily identifiable things that say one brick or another is susceptible. Some observations I’ve made are that orange colored bricks don’t seem to be as hard as red ones, and I’ve seen them spall. King sized brick(the longer brick used more on houses) seem to spall more than modular brick(the shorter ones used on commercial buildings) and also newer brick, produced in the last 25 or so years seem to stand up better than brick from the 70’s & 80’s. The brick manufacturing industry has made major advancements in the last few decades.
Another factor that can lead to spalling is the location of the masonry. Exposed masonry is at a high risk. Things like chimneys, mailboxes, and wing and planter walls. I have two theories on why they seem to sustain damage more frequently. One, since they are exposed, rather than being protected by an overhang and have flat areas where the water can just sit and soak in, they tend to take in more moisture. That one is obvious. Secondly, they aren’t backed up to a heated wall. The walls of a home, no matter how well insulated, leak out heat during the winter. That heat goes into the air space between the wall and the masonry, raising the temperature of the air space and the masonry, therefore those walls don’t freeze as solidly, or as often as exposed walls. Another problem area is the bottoms of walls, they are always at a greater risk than the top. A few of the reasons those areas are at risk; first, they are unprotected from overhangs, even on house walls. Secondly, water always goes down, so any moisture that hits anywhere on the wall will go to the bottom. Once it’s at the bottom, it has nowhere else to go. On a side note, if the grading of the home is off and slopes towards the house, all of the water from that area goes against the bottom of the wall. A third factor in the bottom of the wall is that is where the water hits when you are watering your lawn or plants; it gets way more saturated than higher on the wall. And lastly, heat rises, so how we discussed earlier about the air space being heated and not freezing as often doesn’t apply towards the bottom of the wall. Another unexpected risk factor and troubled area is painted masonry. The paint seals off the masonry and does keep moisture from going into the brick, but it doesn’t allow the trapped moisture to evaporate out. It stays in and freezes. Finally, the last of the common trouble spots is around penetrations. Windows that aren’t properly caulked and scuppers on flat roofs are likely areas. Why? They simply let in water.
Now for the potential problems, left untreated for a long period of time, spalling masonry can completely compromise the structural integrity of your masonry veneer. Yes, COMPLETELY COMPRIMISE THE STRUCTURAL INTEGRITY. We have referred to freeze thaw damage as brick cancer, it’s that serious. The trouble is if one brick or stone spalls, then it allows even more moisture in, which spreads it to the next one, then the next one, and so on until the wall is unable to support itself. It’s one of the more serious types of masonry problems.
How to identify freeze thaw damaged masonry; the first test is visual, look at the problem areas I mentioned earlier. If any are spalled, call a mason. Secondly, if any are discolored or look wet, check them more thoroughly. If the mortar is discolored, look at the masonry units in that area. A good test is to LIGHTLY tap the units with something metallic such as a hammer or pliers. A damaged unit will feel softer, and make a different sound than an undamaged one. Tap around and see if any feel different.
The only fix for spalling masonry after it has started is to replace all the damaged units. You have to cut them out, and lay new units with new mortar. If you don’t have any damage but want to protect against it in the future, there are things we can do to help prevent it. Moisture control is the key. One, if your masonry has what we call a scratched joint, which means the mortar is recessed on the sides and top of the unit, tuck point it in with new, modern mortar and finish it with a smooth joint. That recess allows moisture to sit on the units and soak in. Secondly, spray your masonry with a water repellent. DO NOT USE A SEALER. Sealers significantly increase the likelihood of damage, because they work the same way as paint. Whereas a repellent repels water off the surface but does not interfere with the moisture evaporating out of the wall. I have a product we’ve used for 20 years that I highly recommend. Also, keep your gutters keep and functioning properly. A clogged gutter concentrates moisture into one area, and will cause major damage to a lot of things, not just your masonry. Make sure the grade around your house is sloping away. Pooling water next to a house is one of the top root causes of masonry and foundation problems.
So, there’s a small blog about the freeze thaw cycle. If you have trouble, get it checked out. If you have questions, call me or Raymond at the office. (580)762-9097. We have been dealing with masonry for decades, we can take care of any problems that you might have. Either of us would be happy to help you out.
And check back from time to time, I have many more exciting topics to blog about. Expansion cracks, settlement cracks, maybe even a blog on wood fungus....I know, so exciting you can hardly wait