You can spot bad repointing from thirty metres away. The joints are too proud, too grey, too flat. They sit on the brickwork like grout in a tiled bathroom, and somewhere behind them the wall is quietly getting wetter every winter. That was the situation on the last Georgian facade I worked on, and it is the situation on most of them.
What follows is a full account of repointing a Georgian townhouse facade — the diagnosis, the mortar specification, the sequence, the money, and the three things I got wrong. If you own or manage a pre-1840 brick building, this is what the job actually involves.
Key takeaways
- Hard cement mortar in an old soft-brick wall is the single most common cause of decay, not the cure
- The workable specification is a lime mortar matched in strength and porosity to the brick, with a joint recessed slightly behind the face
- Removal depth should be roughly 15–20 mm or twice the joint width — whichever is less
- Budget on £45–£85 per square metre for scaffolded lime repointing in the UK, with heritage consent work at the top of that band
- The wall must stay damp for days after application, not dry out quickly
Why georgian brickwork needs lime, not cement
Georgian brick is soft. Not "a bit softer than modern" — genuinely soft, often under-burnt at the core, laid in a lime putty mortar that was never designed to be strong. It was designed to be sacrificial. When water gets in, the mortar gives way first. That is the whole point.
Cement mortar inverts this. It is harder than the brick, less porous, and effectively rigid. Water trapped behind it has nowhere to go but into the masonry. On the facade I worked on in Bath — a three-storey terrace from the 1790s — the previous repointing had been done with a 3:1 sand-cement mix, probably some time in the 1970s. By the time I got there, I counted forty-one spalled brick faces on the front elevation alone.
How to tell cement mortar from lime
You do not need a laboratory for the first pass. Try these in order:
- Scratch it with a steel nail. Lime mortar yields and crumbles; cement resists and rings.
- Look at the colour and texture — cement mortar is uniform grey with a sharp, sandy grain; lime is softer, often creamy or off-white, and looks slightly "soapy"
- Check for shrinkage cracks running vertically along the joint. Cement does this. Lime rarely does.
- Tap the brick next to it. A dull thud usually means the brick face has already detached from its core.
If all four point the same way, you have a cement problem and you have a spalling problem, and they are the same problem.
The specification that actually works
Here is where most guides go vague. "Use lime mortar" is not a specification. This is what I now write into every schedule, and it has not failed me yet.
Mortar mix and sand grading
For a Georgian brick of moderate softness, I use NHL 3.5 (natural hydraulic lime) at a 1:2.5 ratio with a well-graded sharp sand. For very soft, under-burnt reds I drop to NHL 2. Aerial lime putty is the purist's answer and it is genuinely better for the softest fabric, but it needs protection from frost and drying, which on a scaffolded terrace is not always realistic.
The sand matters as much as the binder. A single-graded builder's sand produces a brittle, over-rich mix. I specify a 0–4 mm graded sand — coarse grains for body, fines for workability. Add a small quantity of brick dust from the same building where you can; it improves colour match better than any pigment.
What I do not add: cement, PVA, or any "fortifier". Each of those undoes the point of the exercise.
Joint profile and depth
Georgian joints are typically 8–12 mm wide. Rake back to 15–20 mm, or twice the joint width, whichever is less. Below 15 mm you are not removing enough contaminated material. Above 20 mm on a soft brick you start doing damage.
The finish is a slightly recessed joint — flush or a millimetre or two behind the brick face. Not struck with a bucket-handle tool, which crushes the arris and leaves a water trap. Not proud. A flush or faintly recessed joint sheds water and lets the wall breathe. That is all you need it to do.
| Element | Cement repointing (wrong) | Lime repointing (right) |
|---|---|---|
| Binder | OPC or 3:1 sand-cement | NHL 2 / 3.5, or lime putty |
| Relative strength | Harder than the brick | Weaker than the brick |
| Vapour permeability | Low — traps moisture | High — wall dries inward |
| Joint profile | Often proud or struck | Recessed, flush |
| Workable life | 2–4 hours | 24–48 hours (putty: longer) |
| Cure | Dries out | Must stay damp 3–7 days |
| Typical cost | £25–£40/m² | £45–£85/m² |
Method statement: the sequence, in order
Scaffolding goes up first. On a three-storey terrace that is roughly a week of hire before anyone touches a joint, and it will dominate your budget line — expect £2,500–£5,000 for a typical front elevation depending on access.
Then:
- Photograph everything before you start. Elevation by elevation, with a scale. Your conservation officer will ask, and you will want the evidence if a brick fails.
- Rake out by hand or with a small grinder fitted with a mortar-raking blade. Never a wide chisel on soft brick. Never a needle gun.
- Brush the joints clear and remove all loose material.
- Wet the joint down — significantly, and let the suction settle. Dry brick will pull the water out of your mortar before it can cure.
- Fill in two passes: a partial fill to key into the back, then a finish pass once the first has firmed.
- Firm the joint with a churn brush once it starts to go off, then finish with a wooden or plastic tool. This closes the surface without sealing it.
- Cover and keep damp. Hessian over the elevation, misted twice a day in warm weather, for three to seven days. This is the step most contractors skip and it is the step that decides whether the mortar cures or simply dries.
On the Bath job, 62 square metres of front elevation took eleven working days with two people, plus the scaffold week either side. A single-storey elevation on a smaller house can be done in four or five.
Weather and timing
Do not repoint in frost, and do not repoint in direct summer sun. Spring and early autumn are the right windows. If you must work in July, work the shaded elevation first and keep the hessian wet. Lime that dries too fast carbonates badly and you will be back in five years.
Three mistakes I made
The first was choosing the wrong sand. I used a local washed sharp sand on the first elevation and the joints came up harsh, sandy, and far too pale against the brick. I ended up taking off nine square metres and starting again. Cost me about £600 and four days. Match the sand to the existing mortar, not to whatever the merchant has in stock.
The second was underestimating moisture. On the north elevation, a section of wall that had been cement-pointed for decades had soaked up so much water that the new lime mortar took nearly twice as long to go off. It looked fine for a fortnight. It was not fine. We ended up redoing roughly 8 linear metres of joint because it had shrunk away from the brick.
The third — and this one is common — was assuming the roof was not part of the problem. It was. Water coming down the valley gutters had been saturating the parapet for years, far more than any repointing could fix. Fix the water source before you fix the wall. That should be the first line of every schedule I write now, and it was not on the first one.
What it costs, and what it buys you
Across the last few projects, the honest figures look like this. Repointing alone at £45–£85/m², scaffold at £2,500–£5,000 for a terrace front, brick replacement at £25–£60 per brick fitted, plus heritage consent fees if the building is listed. On the Bath terrace, total spend came to a little over £19,000 across 62 square metres of elevation and 41 brick replacements.
What you get back is not aesthetic. It is a wall that can dry itself again. Before the work, a moisture meter on the north elevation read in the high teens as a percentage of weight. Eighteen months after, it sat in single figures. That is the whole job, in one number.
Is it worth it on a building you do not plan to keep? Honestly, yes — but for a reason most guides miss. A cement-pointed Georgian wall is a wall in a slow, expensive decay, and the bill for that decay arrives whether you sell or not. You are not improving the house. You are stopping the clock.
