All About Masonry: Part 1
Best Practices for Maintaining Masonry Buildings
Brick and mortar are so ubiquitous that the term has come to mean a physical presence. That is precisely why this topic is so important. We are not talking about retail sales, we are talking about physical presence, durability, sustainability and economic impact.
Before discussing the technical aspects of masonry maintenance, we should take a moment to pause and look around us. Chances are you are in or near some brick buildings right now. Schooley Caldwell’s office is in a former paint factory with heavy timber framing and brick exterior walls. This building has been around since last millennium! Sure, we are not talking about a thousand-year-old building here, but in the world around us there are several places that have survived for millennia. It is amazing to think that generations ago someone packed some clay and mud into a shaped container, usually a wood frame, baked that muddy lump and now we have buildings and roads that will outlast us.
A little history for perspective
Brick is everywhere around the world. It has been used for thousands of years and we can see the use of masonry dating back to some of the earliest civilizations. We also see brand new brick buildings under construction today. The earliest bricks we know about were made almost nine thousand years ago with mud and straw dried in the sun. We see examples of early bricks in Ancient Egypt and throughout the Americas with some massive structures from the Aztecs that are still intact today. The bricks we are most accustomed to date back about five or six thousand years; that’s when someone had the inspiration to heat up or “fire” the bricks. This technological breakthrough meant we were not as dependent on the sun, and a brick could be made almost anywhere. The Romans made brick and used it throughout their empire for all types of buildings. We see a variety of styles and shapes of bricks, and we see them in walls, arches, and vaults throughout the world.
For a brief moment in the late 1800’s through the 1930’s there was another development for fired clay—glazed architectural terra-cotta, which is seen throughout our cities. More on this later.
If these things last so long, what’s the problem?
Bricks are forever, but mortar needs to be replaced. Maybe there isn’t anything wrong at all. However, it should be noted that mortar is a sacrificial material with a typical life span of 30-50 years. That’s right, the bricks are supposed to last forever but the mortar that binds those bricks together is supposed to be replaced periodically. This doesn’t mean that all bricks are fine and will last forever, but it does mean that with proper maintenance, our homes, offices, and cities could. Our roads and buildings take a non-stop beating: buildings bake in the summer sun, get chillingly cold in the winter, and are subjected to rain and other precipitation throughout the year. Every little crack or break in the mortar joints (or, occasionally, the brick itself) allows moisture to get into the wall where it may freeze, and we all know water expands when it freezes, exerting more pressure on the walls and hastening damage. If you are seeing cracks through bricks or blocks, or maybe a zig-zag crack in a wall following mortar joints (and most likely at a corner of a building), your issue is structural movement and you likely have other issues inside the building, too.
It is hard for us to imagine a building beyond hope of repair and renovation (check out more on that topic in one of our previous whitepapers here: Too Far Gone: a Case Study on the Carlisle Building
Environmental Impact. One other thing I urge you to consider is the real impact of a brick. In the past, when a building was demolished, the materials were often spread across the site and a new building was built above. In just about every single project in downtown Columbus, we encounter remnants of older abandoned buildings, especially the foundations. Today, if we are unable to repurpose materials like reclaimed wood, the debris goes to a landfill. The great thing about a brick is it will never blow away into the ocean to pollute our waters or air, but once our bricks are fired above about 1,000 degrees fahrenheit a chemical change takes place. This change gives brick its color, hardness, and durability. (The goal is to get above 1,700 degrees fahrenheit to form a bit of glass-like material to bind everything together.) This chemical change is called vitrification, and at this point, a brick is as hard and weather resistant as it will ever be and is ready for use in construction. Once a brick undergoes vitrification, the materials will never return to their original state. Remember those 9,000 year-old mud bricks I mentioned? The environmental impact of a sun-fired brick is reversible, but a fired brick is forever. So, we might as well put those materials and embodied energy to good use.
Repairs need to be done right. The majority of issues we encounter in older buildings are the result of well-meaning but bad attempts to fix a problem. We’ve seen people use sealant or caulk to replace cracked mortar, but this traps in moisture, leading to even more damage. We’ve seen people seal, stain, or paint walls, too, and depending on the product and application this can help. However, many times the sealing product traps more moisture in the wall, leading to even more rapid deterioration.
two biggest concerns when dealing with masonry
Pressure Washing or Sandblasting
Think about those open mortar joints: driving water directly at a gap under intense pressure saturates the wall and also risks damaging bricks and mortar even more. Some pressure washers have enough power to permanently etch or scar the face of the building. The solution is really simple – a garden hose applies an appropriate amount of pressure, and a mild detergent with a soft nylon brush or broom can clean off even the most stubborn environmental stains.
Tuckpointing or Repointing a Wall Improperly
This issue is a bit more complex. This past winter I watched a crew working across the street through our studio window. I asked all of Schooley Caldwell’s junior designers to join me at the window and discuss what the crew was doing right and wrong. Our list went on for a while. Outdoor winter work can be hard—imagine shivering while holding a grinder!
Well then, how do I fix & maintain my masonry walls?
The first step is to identify the problem so you can prepare a proper fix. There are several things that can go wrong with making bricks, but for now we want to assume that the bricks we are dealing with made it through a minimum quality control review and that we intend to save things in place. Now we will identify five of the most common issues and strategies to address them:
Spalled bricks. These bricks have some or all of the face material missing. We liken this to a torn sponge—what is left is irregularly shaped, usually pitted, and will suck up more moisture just like a sponge. These bricks can be cut out and replaced.
On the left are bricks where the smooth, water-repellent face is intact. On the right, the bricks have eroded (maybe due to decades of sandblasting and pressure washing) and the smooth face of the brick is long gone, leaving the porous material behind the face exposed.
Cracked bricks. If we are only dealing with one or two, then chances are that these bricks snuck through the quality control process. I’d advise either removing and replacing the brick, or routing and cleaning the crack and carefully injecting a color appropriate epoxy.
If the crack is really a crack in the wall and not just some cracked brick, you should have someone who is qualified investigate. Chances are that the wall can still be saved, but you want to make sure the crack isn’t the result of a bigger problem.
Efflorescence (ef le RES’ ens)—not to be confused with bubbly effervescence. This is a fancy French term that means something like ‘flowering out,’ but what it means to us is white stains on our brick walls, which never looks good. This is the result of salts and minerals traveling through our bricks leaving behind a fine, white powder. It’s a moisture issue and is really common in newly built brick walls; in fact, you should expect it to happen sometime during the first year of building a new brick building. If you are suddenly seeing this in an older brick walls, watch out, because it means water is going in someplace it shouldn’t, like cracked mortar joints. Usually the salts are water soluble and a simple water rinse or rain shower can wash them away. If there are just a few small patches then a stiff brush with some mild detergent should be sufficient. A more stubborn case may require more invasive measures, like using special chemicals. In the past we saw sandblasting used, which does the job quickly, but it also erodes the brick and mortar joints, changing the appearance of the building. Long story short, we say it is never okay to sandblast brick; the best thing to do for efflorescence is to avoid it by using good details and proper installation.
Environmental staining and biological growth. Sometimes our gutters get clogged and water pours over the edge of the gutter leaving mud stains on our walls. Sometimes we have a wall in the shade that gets wet and turns a little green. The most common thing we see is dirt that darkens the wall or ivy that grows over the wall. As charming as an ivy-covered wall may be, that plant is like a vampire sucking the life out of your walls and should be removed. If you really want the ivy, consider a trellis or similar structure mounted in front of your wall. If you are dealing with ivy, just remember to cut it at the base and let it die back before pulling it off—trust us, it is way easier and will minimize additional damage. If you are dealing with other dirt or staining then some mild detergent, a stiff brush, a garden hose, and some elbow grease will solve the problem without inflicting more damage and won’t saturate your wall through open mortar joints.
Deteriorated mortar joints. Even if you do everything right, eventually the mortar will fail. Small cracks grow over time, and eventually mortar may completely fall out of a joint. The solution is to repoint, or as many people call it, tuckpoint the wall. The issue is that there are a lot of factors to consider and getting things wrong could cost a lot of money (and nobody likes wasting money). Consider that mortar comes in different strengths (M, S, O, N) and it is possible to use a mortar that is stronger than the brick. This is a huge problem, because instead of fixing a mortar joint you could end up breaking the bricks! Make sure to use the right kind and strength of mortar first, then focus on the color and composition to make sure the fix looks good aesthetically. Remember, mortar will change color over time, which is why we always demand mock-ups of repointing jobs so that everyone knows what to expect. Apart from mortar type, the single biggest issue in repointing has to do with the actual work. Usually we see signs of a grinder that nicked the brick or, worse, some folks believe all the mortar should be removed along with a tiny bit of brick to get a fresh surface to point. The problem is that if you shave a little of the brick each 30-50 years, then after a while there will be no brick left (see image below). Another thing to remember: mortar goes in wet and cures, so temperatures need to be warm but not too hot. At a minimum the wall and outdoor temperature should be 40 degrees and rising, or it is simply too cold to do the job right. If it’s too hot outside, the mortar will dry out too fast. It’s important to plan repair work for the right time of year, or you may find yourself doing the work all over again.
Brick is a great building material and it affords amazing opportunities to be creative. Proper maintenance is a great way of protecting all the embodied energy and costs in our buildings. If nothing else, please remember to start any repair work with good plans and information, and pay attention to how and when the work will be done.
My next whitepaper will discuss glazed architectural terra-cotta and feature a case study of repairs at the LeVeque Tower.