The face is popping off, and there's red dust every spring
You go out in April and there's a little pile of red grit under the wall. Some bricks have lost their face. A few look like they're turning to powder.
That's spalling. The City of Hamilton's Masonry Restoration Guidelines describe it plainly: the brick breaks down, turns to powder and breaks apart. The same guidelines list the usual causes. Water getting in, repeated wetting, freezing and thawing, and salts crystallizing under the surface are all on the list.
Spring is when you see it because winter did the damage. Water inside the brick can freeze and cause spalling and cracking, as the US National Park Service's Preservation Brief 1 puts it.
Why it spreads once it starts
A spalled brick has lost its hard outer skin. The City's guidelines say bricks form a protective skin when they're fired, and without it they deteriorate. What's left underneath is softer and soaks up more water.
So the wet spot stays wet, and every freeze takes a little more. The Brick Industry Association's Technical Note 46 adds that water gets into the wall through broken or heavily spalled bricks. One bad brick lets water reach the next.
There's a second engine too. When wet masonry dries, salts left behind can crystallize under the surface. The Park Service's Preservation Brief 2 says that pressure can make the outer surface spall off.
Crumbling near the ground, or under the downspout
Look at where the damage is. Spalling often sits low on the wall, under a downspout, or beside the front steps. Those are the wettest spots on the house.
The Park Service's Preservation Brief 39, on unwanted moisture, names the usual sources. Blocked gutters and downspouts soak walls. Rain splashes back onto the base of the wall. Water in the ground rises up into masonry. The same brief warns that de-icing salt can increase freeze-thaw spalling of masonry.
What's safe to check from the ground:
- Does a downspout empty right at the wall, or is the eavestrough above it overflowing?
- Is soil, mulch or a garden bed sloping toward the house?
- Is there a white, salty line low on the wall? That's water rising and drying out.
- Is the damage only by the steps, where salt gets thrown in winter?
No ladders. Don't pick at loose faces, and don't pressure wash or blast the brick. The City's guidelines say sandblasting strips the brick's protective skin.
Someone sealed or painted it, and now it's flaking
This one surprises people. A coating meant to keep water out can trap it in.
The City's guidelines explain that sealing one side of breathable brick lets moisture build up behind the sealer, until the brick breaks apart. Preservation Brief 1 says the same about waterproof coatings: if water gets in from the ground or inside, it can't escape, and in cold weather it freezes and spalls the brick. The Brick Industry Association says film-forming coatings shouldn't go on exterior brick at all.
So don't add another coat to fix it. Every coat traps a little more.
When a brick can stay, and when it needs replacing
Start with the water, not the brick. The Brick Industry Association says to find and correct the source of moisture before other repairs. Otherwise new bricks go into the same wet wall.
Then look at each brick. The association draws the line at bricks that are broken or heavily spalled, because water gets in through them. Those usually need replacing. A brick with a shallow flake and a solid face is a judgment call. We make it on site, once the water problem is fixed.
Stop and call if the damage is spread across a wall, or bricks are loose. Also call for cracks that step diagonally through the joints, or a wall that leans. The association lists widespread spalling and stepped cracks among signs that can point to a structural problem.
What we do: brick repairs on older Hamilton houses. We cut out the bricks that are done and set in matching ones. Then we fix the mortar joints around them. Replacement brick has to match the old in colour, texture and size, and in how it behaves, the association notes.
Why the mortar has to match
This is where a lot of past repairs went wrong. Mortar is meant to be the weak link.
The City's guidelines call mortar a sacrificial part of the wall. It's meant to wear out over time, so the bricks don't. Mortar for repointing (replacing worn mortar in the joints) should be softer or more permeable than the bricks. Mortar stronger than the brick causes permanent damage, such as cracking and spalling.
Preservation Brief 2 explains why. Hard mortar won't give, so the stress goes into the bricks instead. It also won't let moisture out, so the water stays in the brick and the faces pop off. The Brick Industry Association warns that the wrong mortar may cause spalling and cracking in the existing brick.
That's why a quick cement patch on old brick often comes back worse. The City's guidelines name cement used as a quick fix as a common cause of salt damage.
If your house is designated heritage
The City of Hamilton's Heritage Permits page says designated properties need a heritage permit for alterations affecting their heritage values. It lists masonry cleaning and repointing among work that needs one. It also lists painting previously unpainted masonry. Small repairs with the same materials usually don't.
If you're not sure your house is designated, ask the City's heritage planning staff before any work starts. For other City rules, see Hamilton permits.
What it costs
Spalling brick repair is priced at the free in-home consultation, once we've seen the wall. It depends on how many bricks are done, where the water comes from, and what the mortar needs.
For the full picture of our stone and brick work, see brick repair in Hamilton.
Mortar crumbling too? Read what crumbling mortar and white stains mean.
