Introduction
Seen a wall that was repointed only a few years ago and it’s already powdering, cracking, or letting water in? You’re not alone. Many contractors see repointing fail because the mortar was too hard or too weak, the joints were undercut by grinders, or the work was done in the wrong weather. In this guide, I’ll break down why repointing fails, how to diagnose the real problem, and how to fix it so it lasts. We’ll cover mortar selection, site conditions, execution details, and a simple way to scope jobs clearly so you don’t end up with callbacks.
Table of Contents
Key Takeaways
- Most early failures come from the wrong mortar or poor weather control. In general, keep work between 5–30°C and protect from frost and direct sun for 48–72 hours.
- Rake to the right depth: commonly 15–25 mm or about two times the joint width. Clean thoroughly before refilling.
- On older, softer brick or stone, a lime-based mortar (often NHL 3.5 at 1:2.5–1:3 with sharp sand) protects the masonry better than a strong cement mix.
- Good curing is as important as the mix. Aim for initial set in roughly 4–8 hours and controlled damp curing for 2–3 days.
Diagnose The Repointing Problem Properly
Many contractors jump straight to grinding and filling. That’s where the problems start. Failures come from mismatched mortar strength, moisture issues, or movement that mortar alone can’t fix.
The Problem
- The wall leaks in wind-driven rain, the joints are crumbly or hollow, or there’s blistering/spalling around hard, grey cement infills on soft brick.
- Commonly, previous repointing was done too shallow (less than 10 mm), overworked on the face, or smeared across brick arrises.
- Salts (efflorescence) or trapped moisture can blow fresh joints if they’re sealed too tight.
The Solution
- Map the wall by elevation. Note exposure, orientation, and any drip edges or failed flashings. Many contractors find that top courses and corners take the worst weather.
- Test the existing mortar: simple scratch test, pick test, and compare hardness to the brick/stone. Mortar should generally be the sacrificial element.
- Check for salts: white crystalline deposits, damp lines, or hollow-sounding render/paint. If salts are active, plan for gentle desalination and breathable mixes.
- Confirm joint dimensions. In general, older brickwork has 8–12 mm joints; aim to rake 15–25 mm (or two times the joint width) for a solid key.
Example
A 1930s front elevation with hard cement pointing on soft bricks. The face bricks are spalling around the joints. Diagnosis: mortar too strong and too impermeable. Solution: carefully rake 20 mm, switch to NHL 3.5 at roughly 1:2.5 sand, manage curing 72 hours with hessian, and reinstate drip lines under the sill.
Choose The Right Mortar
If the mortar is wrong, it won’t matter how neat the finish looks. The mortar must be compatible with the masonry, the exposure, and the building’s movement and moisture behaviour.
Overview
| Mortar Type | Where It Fits | Pros | Risks |
|---|
| NHL 2 / NHL 3.5 lime with sharp sand (e.g., 1:2.5–1:3 by volume) | Older/softer brick and stone, mixed substrates, heritage or breathable walls | Flexible, vapour-permeable, kinder to soft masonry | Slower set; needs good weather control and curing |
| Cement:sand (e.g., 1:3–1:4) | Dense, hard brick/block, modern cavity walls, sheltered elevations | Faster set, early strength | Too stiff on soft bricks; can trap moisture and drive spalling |
| Prematched/coloured proprietary mixes | Matching specific tones/textures on visible facades | Consistency of colour and grading | Still must respect strength and breathability requirements |
The Problem
- Using a strong cement mix on soft, historic brick often locks moisture in the brick, not the joint.
- Colour and texture mismatches scream “patchwork” and annoy clients.
The Solution
- Match strength to substrate. A good rule on pre-1950 solid walls is to err on the softer, breathable side (commonly NHL 3.5). On modern dense brick/block, a cement-based mortar is acceptable.
- Match sand grading and colour. Local sharp sand and test panels help. Many contractors report better visual results after building a small sample panel first.
- Workability: plasticisers are not a shortcut for wrong mix; adjust sand grading and moisture content instead.
Example
Victorian terrace, solid brick, south-west exposure. Trial panels with NHL 3.5 at 1:3 using local sand produced the best colour after curing. The cement-based sample looked flat and caused hairline cracks at the arrises. The lime option was chosen and finished weather-struck.
Execute The Repair Correctly
Good materials still fail with poor prep or rushed finishing.
Preparation
- Rake depth: in general, 15–25 mm or two times the joint width. Avoid deep cutting discs close to arrises; use mortar rakes/chisels with dust extraction.
- Clean: blow/vacuum dust, then lightly wash. Pre-wet to a saturated surface-dry (SSD) condition so the substrate doesn’t rob water. Commonly, a light mist and a 3–10 minute wait does the job.
Placement and Finishing
- Pack from the back in layers if the joint is deep. Compact well; voids cause early failure.
- Joint profile: flush or weather-struck sheds water best on exposed walls. Recessed joints on exposed facades often hold water and dirt.
- Timing: strike/brush when the mortar is thumbprint hard, not plastic. Overworking brings fines to the face and weakens the skin.
Curing and Protection
- Temperature: work between 5–30°C. Keep frost and direct sun off for 48–72 hours. Many contractors find hessian plus light misting works well in warm, windy weather.
- Setting: expect initial set in roughly 4–8 hours depending on conditions; plan site protection accordingly.
Example
Rear elevation, windy site. The team phased the wall in 2 m bays, kept joints shaded, and covered fresh work with damp hessian and mesh to stop “washing out” in a forecast shower. The finish was consistent, and no hairline map-cracking appeared.
Weather, Salts, And Movement
Not every leak is a joint problem. The wall needs to move and breathe.
The Problem
- Wind-driven rain gets behind defective flashings, copings, or sills. Repointing the face alone won’t fix that.
- Hygroscopic salts and trapped moisture blow joints from behind.
- Long runs of brickwork crack because there’s no movement joint.
The Solution
- Deal with moisture sources first: cracked copings, blocked cavity trays, missing drip edges. Repointing is not a magic umbrella.
- Salts: consider gentle poulticing and breathable finishes. Avoid sealing paints that trap moisture in solid walls.
- Movement: in general, long brick elevations need movement joints around 10–12 m apart; tie your expectations to what’s there. Never bridge an existing movement joint with hard mortar.
Example
Parapet wall leaking into the bedroom below. The “repoint and paint” fix failed twice. Final solution: rebed coping stones with a flexible detail, add a proper drip, then repoint the facework. No more ingress in the next heavy rain.
Pricing, Scoping, And Prevention
Clear scope prevents “you didn’t include that” arguments and saves you the second trip.
The Problem
- Vague scopes: “Repoint front wall” with no area, depth, joint profile, or curing method.
- Missed add-ons: access, protection, disposal, sample panels, colour matching.
The Solution
- Measure by elevation. Note square metres for general areas and linear metres for features (corners, parapets, reveals). Include rake depth (e.g., 20 mm), joint profile (weather-struck/flush), and curing/protection plan.
- List contingencies: “If soft face bricks are found behind hard cement, allow for local brick repairs at £X per unit.” Contractors often report that this single line prevents margin bleed.
- Document with photos and a simple sketch marked with arrows and measurements. Many contractors find this reduces back-and-forth by half.
Fast, Clear Proposals With Donizo
- Talk your scope on site: use Donizo to capture details by voice, text, and photos. It turns that into a clean, professional proposal quickly.
- Send the branded PDF by email with client portal access, get a legally binding e-signature, and convert accepted proposals to invoices in one click. For paid plans, you can track payments and keep your office admin tight.
Example
On a semi-detached front elevation, you record: “Rake 20 mm, NHL 3.5 1:3, weather-struck finish, 18 m² facework, 12 lm reveals, sample panel included, damp curing 72 hours, waste off-site.” Donizo generates the PDF, you send it the same day, the client e-signs, and you’re scheduled. No late-night typing.
Frequently Asked Questions
How Deep Should I Rake The Joints?
In general, 15–25 mm or about two times the joint width. Too shallow (less than 10 mm) often leads to debonding and hollow joints. Avoid undercutting bricks and always clean the joint thoroughly before refilling.
Lime Or Cement — Which One Should I Use?
Match the mortar to the masonry and exposure. On older, softer brick or stone, a lime-based mortar (commonly NHL 3.5 at around 1:2.5–1:3 with sharp sand) is usually safer and more breathable. On dense, modern brick/block in sheltered conditions, a cement:sand mix (around 1:3–1:4) can be appropriate.
Can I Repoint In Winter?
You can, but protect it. Aim for temperatures above 5°C and frost-free for at least 48 hours. Use covers, hessian, and controlled curing. Freezing during set will wreck the bond and surface.
How Long Does Proper Repointing Last?
Commonly, well-executed repointing lasts 20 years or more. Lifespan depends on exposure, substrate, mix compatibility, and curing. Poor curing and hard mortar on soft bricks are the usual lifespan killers.
How Do I Match Colour And Texture?
Use local sands, trial panels, and let samples cure fully before judging. Final colour often lightens over 24–72 hours. Don’t rely on dyes alone; sand grading has a big impact on texture.
Conclusion
Repointing fails when we fight the wall: too hard a mix, rushed prep, or zero weather control. Diagnose first, choose the right mortar, respect the weather, and cure properly. Scope clearly so everyone knows what’s included. If you want to cut admin time, capture the job by voice and photos with Donizo, send a professional PDF for e-signature, and convert the accepted proposal straight to an invoice. That’s hours saved and fewer callbacks.
