Mastering The Art Of Masonry Repair: The Dos and Don’ts

Words: John Bard
Photos: Qualprax Masonry

Whether we specialize in repairs and restoration work or new construction, repairs are something that we all must do, at least from time to time. With ever-increasing competition from faster and cheaper building systems, the onus is on us as masonry professionals to do the very best job possible to maintain masonry’s viability in this competitive marketplace.

While this article will be far from an exhaustive list of best practices, as I’m sure our readers have many they could contribute as well, it is my goal to share some insights I have gleaned from 26 years in the field that may be of benefit to some of our readers, particularly our younger masons who are just starting. I have divided this article into two main repair practices that are most frequently encountered by masons. They are individual brick replacements and repointing. With a third section on tooling to match, which pertains to all repair functions but is of enough importance to deserve its own attention.

Individual Brick Replacements
I always called these “cut-ins,” and so for the sake of expediency, that’s what I will refer to them as from here on out. How we refer to them is far less important than how they are done. The first step in this process is, of course, determining which bricks to replace. This is easy when the damage sustained is clearly obvious. But it’s not always that simple.

Deterioration of anything is not a simple change of state, but a gradual degradation. So, some bricks may have spalled faces that have not yet fallen away from the brick substrate. To even an experienced onlooker, they may appear perfectly fine. The easiest way to detect these hidden failures is by sound. A light tap on a healthy brick should sound solid and firm. Tapping on a brick with a spalled face will sound hollow. The difference in sound will be far easier to detect than it is to describe here. If the brickwork has raked joints, which more frequently causes brick spalling, you may also be able to see a fine hairline crack running the length of the brick along the top or bottom edges (photo).

In areas where tapping the bricks is not feasible, I tend to factor in replacing the bricks adjacent to the visibly spalled ones, as they are most likely on their way out as well. As soon as you start working on the target brick, the adjacent ones’ need for repair will become readily apparent.

The Process
Now that I know the bricks I want to replace, I start by cutting the top and bottom joint completely through with the 14” cut-off saw. This can take some practice. Go slow and be careful. Then I take an SDS-plus chisel that I modified for the purpose and pulverize the head joints on either side. This releases the brick as one solid with far less stress on the wall than jackhammering the brick into pieces.

Here comes an axiom for anything to do with masonry. Are you ready? ANY time you are rubbing two masonry surfaces together, they should both be buttered with mortar. If you have ever been told to “double butter closures,” well, every cut-in is a closure. My preferred tools for this are a margin trowel, as its shape and size allow me to butter the sides of the opening completely, and a pointing trowel for everything else. But these two can be used interchangeably.

Mortar should always be as soft or softer than the original. I lightly butter the two sides and the bottom of the brick going into the wall and the matching sides of the opening. I also like to run a bead of mortar down the back side of the top of the brick. This will “roll” slightly as you insert the brick and act as a backer for slicking in the top tighter without pushing the mortar out the back.

Holding the brick on the back of your trowel, slide it into place, hold the brick in place, and withdraw the trowel. Carefully cut off the excess that scraped off the brick without smearing the wall, and then use that mud to slick it tight all around and WAIT. Let the mud tighten up and then tool it to match the surrounding wall. (More on that later).

Repointing
Not to be confused with “tuckpointing,” repointing is a common process that most masons have done, for better or worse. This is the process that I see fumbled more than any other. Like many things in life, there’s more to it than meets the eye, and attention to detail separates the professional from the amateur. The problem is that aside from appearance, a bad job may not be detectable for many years, long after the check has been cashed and the offending party is long gone. If we want masonry to remain a popular choice, we owe it to ourselves, to the industry, and to our clients to get this right.

This can obviously vary from place to place, but one of the biggest challenges with repointing is moisture management. Hot summer weather, thirsty brick, and small, thin applications of mortar mean moisture retention should be of utmost concern. The process I will outline here is a nice “hybrid” method that is fast, high-quality, and yields good results. For the sake of article length, we’re not getting into historic restoration repointing or talking about the methods laid out by the National Park Service or anything like that. Just a nice way to do the regular repointing jobs you will most often encounter.

Process
We use a grinder with a 4.5”x ¼"-3/8” diamond wheel and a vacuum attachment. I know many sources will say not to grind the head joints, as you can nick the brick. The problem with not doing this is that it takes longer and drives up costs. We grind heads CAREFULLY and the beds to a depth of ¾" to 1”. Heads may not be able to get this deep. Be careful not to nick the brick.

Once it’s all ground out, you’ll notice the shape of the heads is semicircular with little spandrel pieces at the top and bottom. I take a plugging chisel and go along and knock these off, as this allows us to get more mortar in and eliminates that shape that tends to eject new joints over time.

Sometimes you’ll find that the wheel didn’t completely remove the joint, and there is a tiny thin wafer of mortar still against the brick. This oftentimes will come out by just gently wiggling the chisel up and down in the joint, breaking it loose, but be careful, as some brick edges are sensitive to this process. This can also be cleaned up with the grinder.

Once we have nice bare sides on the brick, I give it a good spray with a hose top to bottom. This cleans away dust that impedes the bond and gives the wall a drink. Ideally, we want to be SSD “saturated surface dry”. If the bricks are not very absorbent, as is the case with some highly fired bricks, then you may want to skip this wetting step. Or if the weather is cool and damp, you could also skip this step. Use your best judgment and observe how quickly the mortar takes off. Adjust the process as needed.

If you do skip the wetting, you will want to vacuum the wall down to remove dust. Why not just brush? Well, brushing tends to sweep the dust off the brick surfaces and deposit it precisely where you don’t want it, in the joints. Now that it’s clean and ready to fill, we use the humble grout bag. After mixing mortar that is as soft or softer than the original, I do a first application, bringing the mortar out about halfway.

Following up with a slicker, I press it firmly to ensure the mortar is to the back of the joint. Then I top it off with another grout bag pass, leaving it slightly proud. I like leaving it proud because I don't like having to fill tiny holes. Cut this proud mortar off flush after it has firmed a bit. Once the mortar has firmed up to the desired point for tooling, we tool to match the existing wall. If this work receives sun and drying wind, I like to hang a cover over it for the night after it’s had one final misting of water, if the mortar will allow it. Be careful not to wash the mortar out and make a mess. Careful observation is critical with repointing. Chimneys can just be cling-wrapped for the night and covered with a tarp or canvas.

Tooling To Match The Existing Wall
This point is so important that it gets its own paragraph. Too often, we see offensive eyesores of carelessly concave jointed repairs on a wall where no such joint exists. It is by some combination of ignorance, inattention, and apathy that these mistakes occur, and it reflects negatively on all of us and the trade. Nothing diminishes otherwise good work more than careless tooling.

Typically, we are doing repairs on walls that have weathered. This weathering erodes the joints, deepening them slightly. New repairs should have a finished joint depth that perfectly matches this level of erosion. The new joint should seamlessly flow into the existing work. If you ever need to know what jointing method to perform, the wall will tell you. Just look. Sometimes this slight “rake” of the joint from weather can be effectively accomplished by concave jointing, then following up with a stiff brush. But conditions need to be perfect for this; don’t brush soft mortar into brick faces. This method gives you the weathered concave look that is very common. Concave in the middle, with the sharp edges of the brick knocked off, revealing the edge of the brick.

Above: A close-up example of concave jointed repoint work up against original weathered concave joints. The difference is readily apparent and looks even worse when viewed at a distance.

This little detail makes a tremendous impact on the final appearance and makes your work stand out as being top-notch. This slight rake can also be accomplished with a skate set to depth, which can be an effective way to accomplish this, especially for apprentices.

Another weathered joint I see a lot is basically, for lack of a better term, a weathered beaded joint. This was never originally beaded. But the expansion and contraction of brick units combined with weather can cause the mortar to dry quicker at the joint edge where it meets the brick than in the middle of the joint. Over time, this takes on a convex profile. When tooling to match these, I work my inner shape as necessary, then follow up with a careful cut, running my pointing trowel or slicker along the edge of each brick, basically tracing its shape and revealing the brick edge. A light brush with a soft horsetail, and this joint matches nicely. It’s not hard to do, it just takes some time and attention. It should be noted as well that on old buildings, mortar joints can vary around the building. No one technique needs to be employed universally. Let your inner artist come out and match the surroundings.

And of course, all work benefits greatly from a detergent wash once set up. This removes any film on the faces from brushing, makes the exposed brick edges pop, and etches the mortar, revealing the aggregate, as will be the case in the rest of the wall. Washing is always highly recommended for the best work.

Above: An example of the “weathered convex” joint and a matching repair directly in the middle of the photo.

Expounding further on these topics could fill a book, and it has, many times over. I encourage anyone interested in furthering their knowledge to avail themselves of these resources. Here, I have given my best effort to succinctly deliver what I feel are the points that deliver the most impact. But to anyone who made it this far, I thank you for your interest and wish you the best in your continued effort to advance the skills of this fine craft, preserving it for us and future generations.

Mastering The Art Of Masonry Repair: The Dos and Don’ts

About: Technical Talks

The Evolution of Brick Staining: From Color Complaints to Industry Essential

Is Contact with Wet Mortar or Grout Dangerous?

Vibing Masonry #11: Innovative Concrete Masonry Technologies in Healthcare Design

Why Termination Bars Still Matter: A Practical Look at Long‑Term Flashing Performance