Crumbling Mortar Joints
Soft crumbling joints, gaps between bricks, mortar falling out when you brush it — your wall is overdue for proper repointing.
Mortar does not last forever. On Sydney buildings 80+ years old, the original lime mortar weathers out of the joints and needs repointing. Many old buildings have been incorrectly repointed with cement mortar in past decades, which is too rigid for soft heritage brick and actively damages the bricks themselves. The correct fix is lime mortar matched to the original, raked and pointed by hand — it lasts 40–60 years when done properly. Romans Building Services assesses crumbling mortar joints across Sydney before recommending repair, so the visible damage and the cause are both dealt with.
Last updated: 2026-05-29
What is crumbling mortar joints?
Mortar does not last forever. Original lime mortar on a 120-year-old terrace has been weathering for a century, and at some point the joints stop holding water out. When mortar fails, water gets into the wall. Water in the wall damages brick faces, rusts any internal metal, and eventually causes structural problems.
A huge amount of Sydney brick is around this age — Victorian and Federation terraces, Interwar homes, old warehouses. Most need repointing at some point, and many have already been repointed incorrectly with hard cement mortar, which is now actively damaging the bricks it was meant to protect.
Proper repointing is about more than just filling the joints. The mortar mix has to match the brick strength (soft brick = soft mortar), the profile has to match the original, and on heritage buildings the aesthetic finish has to be right. Done well, it lasts 40 to 60 years.
Signs to look for
- Mortar crumbling or powdering when you scratch it with a key
- Visible gaps in mortar joints, especially on exposed elevations
- Bricks loose in the wall — moving when pushed
- Water stains or damp patches inside appearing where mortar has failed outside
- Plant growth in joints (moss, weeds, small plants)
- Hard grey cement pointing next to softer original mortar
- Brick faces spalling — surface flaking away
Why it happens
- Age — original lime mortar has weathered out over a century
- Cement repointing from past decades now damaging the bricks
- Salt crystallisation in joints breaking down the mortar
- Water ingress from failed flashing, gutters or damp
- Wrong original mortar mix — too weak or too strong for the brick
- Freeze-thaw cycles slowly fracturing the mortar (minor in Sydney but happens)
How urgent is this?
Crumbling mortar is usually a years-long problem, not an emergency. But it is not going to fix itself, and every year you wait the cost grows as water damage spreads into the bricks themselves. For heritage buildings, doing it properly with lime mortar before the bricks are damaged beyond repair is the right call.
How we fix it properly
Inspect and mix-match
We assess the existing mortar — age, composition, colour, profile — and work out what the original mix was. We take samples, test them if needed, and mix replacement mortar to match. For heritage work this is the most important step.
Rake out old mortar by hand
For heritage brick, we rake out joints by hand with chisels or specialist tools — never with angle grinders, which damage soft brick faces. Depth is usually 15–25mm. Slow work but essential for old buildings.
Wet the joints
Old dry brick sucks water out of fresh mortar too fast, which weakens the bond. We pre-wet joints so the mortar cures properly. Sounds simple but making this step is one of the reasons old repointing jobs fail.
Point the joints correctly
Lime or lime-cement gauged mortar, pushed into the joints firmly, tooled to match the original profile — flush, raked, struck, weathered, or tuck pointed depending on the building. Colour-matched to the existing.
Cure slowly
Lime mortar needs slow, damp curing. We cover the work, mist-spray for several days, and protect from direct sun or heavy rain. Rushed curing is why some repoints fail in 5 years instead of 50.
Typical cost range
Front facade of a single-width terrace typically $8,000 – $15,000. Full external repointing on a terrace usually $20,000 – $40,000 depending on access, condition and tuckpointing.
Every job is different. We give a firm quote after inspection.
Common questions
Why is cement pointing bad for my old brick house?
Old bricks are soft and permeable — they need to breathe. Cement mortar is too hard and too impermeable. Water that gets into the wall cannot escape through the hard cement joints, so it escapes through the soft bricks instead, damaging them. In 30–50 years, you end up with cement joints intact and bricks destroyed.
What is tuckpointing and does my terrace have it?
Tuckpointing is a decorative technique where dark mortar fills the joints, and a fine line of white putty is run through the centre of each joint to create the illusion of very fine, precise brickwork. Common on higher-end Victorian terraces in Paddington, Newtown, Leichhardt and similar areas. If your brickwork has thin white lines running through dark joints, yes.
How long does proper lime repointing last?
40 to 60 years with proper specification and installation. Some original lime mortar on Sydney terraces has lasted 120+ years — we are just replacing what time has finally worn out. Cement repoints typically fail earlier, often 20–30 years, because the harder mortar accelerates brick decay.
Can you match the original mortar colour and style?
Yes — on heritage work, matching is central to the job. We take samples, mix trial batches, and test against the existing before committing to the scope. Colour, texture and joint profile all get matched so the repoint is barely noticeable.
Services that fix this
Crumbling Mortar Joints in your area
The causes and right fix for crumbling mortar joints vary with local housing stock and exposure. Read the version closest to where you are:
Where we see crumbling mortar joints most often
Some suburbs have more of this problem than others — the local housing stock, age, and coastal exposure all play a part. Click through for the local context.
Think you might have crumbling mortar joints?
Send a photo or call Minas directly. We will tell you straight whether it needs doing now, or whether it can wait.