Brickwork has a reputation for lasting a long time, so it can be surprising to notice the material between the bricks beginning to crack, flake or disappear. The bricks themselves may still look perfectly solid while the joints around them are clearly showing their age.
That material is mortar, and it plays an important role in the wall rather than simply filling the gaps. Mortar helps bind the masonry together while also dealing with moisture and normal movement. When deterioration becomes significant, repairs such as Brick Repointing may be needed to remove failing mortar and replace it with a suitable new mix.
But why does mortar deteriorate in the first place? Usually, there isn't one dramatic event. It's the result of years of exposure, moisture, movement and weathering gradually taking their toll.
Mortar Naturally Ages
Nothing on the exterior of a building escapes ageing.
Mortar spends its life exposed to changing temperatures, wind, rain and other environmental conditions. Over many years, these repeated stresses can gradually weaken its surface.
You may first notice small cracks or areas where the mortar looks slightly sandy. Eventually, sections can begin falling away when touched.
Older mortar isn't automatically defective. In fact, many masonry walls remain in good condition for decades. The important question is whether deterioration has reached the point where the joints are no longer performing properly.
Water Is a Major Contributor
Moisture is one of the biggest influences on masonry.
Rain can enter small cracks and deteriorated joints. If water repeatedly penetrates the same areas, it can contribute to further breakdown.
In climates where temperatures fall below freezing, trapped moisture creates another problem. Water expands when it freezes, placing pressure on surrounding materials. Repeated freeze-and-thaw cycles can gradually enlarge cracks and loosen mortar.
Even without freezing temperatures, persistent moisture can accelerate deterioration.
This is why it's worth investigating where water is coming from rather than simply repairing the most obvious damaged section.
Gutters and Drainage Can Affect Your Walls
Sometimes the problem begins somewhere above the brickwork.
A leaking gutter, damaged downpipe or poorly directed drainage system can repeatedly dump water onto the same section of wall.
Over time, that concentrated exposure may leave the mortar in one area looking significantly worse than the rest of the building.
Before repairing damaged joints, look for patterns.
Is deterioration concentrated underneath a gutter? Is water running down the wall during heavy rain? Does the bottom of the wall remain damp?
Fixing the source of excessive moisture can be just as important as repairing the mortar it damaged.
Buildings Move More Than You Might Think
Buildings aren't completely motionless structures.
Materials expand and contract as temperatures change. Foundations can settle, and minor movement can occur throughout the building over time.
Mortar needs to accommodate some of this movement.
Small cracks don't always indicate a major structural problem, but significant, widening or recurring cracks deserve closer attention.
If cracks run through both bricks and mortar, appear suddenly or continue growing, it may be worth obtaining professional advice before treating the issue as ordinary mortar deterioration.
Previous Repairs Can Cause Problems
Not every mortar repair is a good repair.
The replacement mortar needs to be compatible with the existing masonry. This becomes particularly important with older buildings, where the original bricks and mortar may behave differently from modern materials.
Using mortar that is too hard or unsuitable for the surrounding brickwork can potentially create new problems rather than solving the original one.
Masonry systems need to work together.
That's one reason matching a repair isn't simply about choosing a mortar that looks roughly the same colour.
Poor Workmanship Can Shorten the Life of Mortar
Mortar can also deteriorate prematurely if it wasn't properly mixed, applied or cured in the first place.
Too much or too little water, inappropriate proportions, poor joint preparation and unsuitable weather during application can all affect the finished result.
A thin cosmetic layer applied over deteriorated mortar may look better temporarily but won't necessarily provide a durable repair.
Proper restoration generally requires removing unsound material to an appropriate depth before new mortar is installed.
What Does Failing Mortar Look Like?
You don't need specialist equipment to notice many early warning signs.
Look for:
- Mortar that crumbles when lightly touched
- Visible gaps between bricks
- Cracked or missing sections
- Joints that appear deeply recessed
- Dampness around deteriorated areas
- Loose pieces collecting near the base of the wall
- Sections that look noticeably different from surrounding mortar
Photographing problem areas every few months can also help you see whether deterioration is progressing.
Don't Ignore the Cause
Replacing deteriorated mortar can restore damaged joints, but it's worth asking why those joints failed.
If the cause is simply decades of normal weathering, repair may be relatively straightforward. If a leaking gutter is continually soaking the wall, repairing the mortar without fixing the gutter leaves the underlying problem in place.
Likewise, unusual cracking may require further investigation before any cosmetic repair begins.
A masonry professional can assess the condition of the mortar, the bricks themselves and the likely cause of the deterioration.
Crumbling mortar doesn't necessarily mean your brick wall is about to fail, but it shouldn't be ignored indefinitely. Mortar is designed to play an active role in protecting and supporting masonry, and deteriorated joints can allow more moisture into the wall.
Check your brickwork occasionally, particularly around areas exposed to heavy rain or drainage problems. Catching deterioration while it's still localised can make it easier to understand what's happening and deal with the cause before a small patch of crumbling mortar becomes a much larger repair.