Brick Jointers: Which Profile, Which Size, and How to Use One

Your brickie finishes the gable wall at three in the afternoon and packs up. You look at the elevation the next morning and the joints are flat and flush instead of the concave profile on the rest of the house. The only fix now is raking out every joint on that panel and repointing, because the mortar has already gone off. A brick jointer costs under a tenner and a thirty second conversation with the bricklayer would have prevented it. This is the tool that decides how your extension looks, and nobody explains it to the people paying for the work.

What it is and when you need one

A brick jointer is a short length of shaped steel, usually mounted on a handle or bent into a cranked shape, that you run along fresh mortar joints to compact and finish them. The shape of the steel determines the profile the joint takes: a rounded bar leaves a concave "bucket handle" finish; an angled blade leaves a weather struck slope; a V-shaped point leaves a V-joint; a flat edge gives you a flush finish.

The jointer does not fill the joint. That job belongs to the brick trowel as the wall goes up, or to a pointing trowel during repointing. The jointer is the finishing tool. It comes out once the mortar has stopped being wet and has firmed up to the point where it can hold a shape. Miss that window and the joint either smears (too early) or drags and tears (too late). The window can be as short as fifteen minutes in hot dry weather or as long as an hour on a cold overcast day.

You need a jointer whenever fresh brickwork is being finished to a visible profile. That covers new extension skins, repointing weathered walls, patching mortar on garden walls, and matching existing joints on a period property. For most UK new-build brickwork the profile is concave bucket handle, and a 10mm bucket handle jointer is the tool doing the work.

Profiles, and why the era of your house decides

The profile is the finish. Five profiles cover virtually all UK residential brickwork, and the right one depends mostly on when your house was built.

Click to enlarge

Bucket handle (concave). The default on UK new builds since roughly the 1950s. A rounded bar is drawn along the joint to compress a smooth concave curve into the surface. It sheds water well, tolerates slight inconsistencies in joint width, and forgives a beginner's hand. If your extension is a modern build or you're adding to a post-war semi or detached, this is almost certainly what you want.

Weather struck. The Victorian and Edwardian standard. The top edge of the horizontal joint is pressed deeper, leaving a downward slope that throws water clear of the brick below. Harder to execute consistently. If you're extending onto a Victorian terrace, London stock brick facade, or a pre-WWI property with original weather struck joints, using bucket handle instead will stand out immediately.

Flush. Mortar cut level with the brick face. Becoming more common on contemporary new builds where the architect wants a crisp minimalist elevation, and standard on interwar concrete-era brickwork from roughly 1920 to 1940. Simple to finish but unforgiving: any mismatch in mortar colour or sand grading shows.

V-joint. A clean V-groove pressed into the mortar. Uncommon on UK residential but occasionally specified on commercial or feature panels. Also, crucially, the profile you actually get if you buy a Ragni jointer thinking it's a bucket handle.

Ruled, struck and cut, and tuck pointing. These cover the heritage end. Ruled joints (a straight scored line through the mortar) were common on 17th and 18th century brickwork. Tuck pointing (a thin white lime ribbon laid over a coloured background) was a Victorian status finish found on premium Georgian and Regency frontages. Neither is a homeowner job. If you own a listed or conservation-area property with tuck pointing, get a heritage bricklayer.

The rule of thumb: survey a sheltered section of original elevation (under an eave or beside a downpipe, where weathering is least), identify what's there, and tell your bricklayer before a single brick is laid. Matching is non-negotiable on period properties and a planning condition in conservation areas.

Sizing: matching the jointer to the joint

UK brickwork is built around a nominal 10mm mortar joint. Standard brick coordinating sizes assume it. Blockwork runs slightly wider, usually 10mm but sometimes up to 15 or 16mm for concrete blocks laid with coarser mortar.

The jointer width has to match the joint width, or close enough. Pick a jointer that's narrower than the joint and it sinks in too deep, leaving a groove that looks starved and collects water. Pick one that's too wide and it rides on the brick edges without compacting the mortar, leaving a weak surface.

Marshalltown dominates the UK retail market and their sizing is imperial. The two numbers on the packaging are the widths of each end of a double-ended tool. Translating them matters because nobody measures bricks in inches anymore.

The M83 is the one to buy for a standard extension. If you're working on older brickwork where the joints have weathered to 12 or 14mm, the M80 will match better. Faithfull Prestige, OX Pro, and Footprint all make equivalents in similar size brackets.

How to use it properly

The tool itself is simple. The technique has three decisions baked into it: when to start, the order to work in, and how much pressure to use.

The thumbprint-hard test

Fresh mortar is too wet to take a profile. Set mortar is too dry to compact. The window between them is where jointing happens, and the only reliable way to find it is the thumbprint test.

Start checking around ten minutes after the mortar goes down. Press your thumb into a joint. If it leaves an impression and your thumb comes away clean, the mortar is ready. If mortar sticks to your skin, wait. If your thumb barely dents the surface, you've waited too long and you're into repointing territory.

Temperature, wind, and mix consistency all move the window. A stiff mortar mix on a warm breezy day can be ready in twelve minutes. A wet mix on a cold damp afternoon might take forty-five. Brickies who work the same site every day develop a feel for it. Homeowners hiring in trade should ask the bricklayer to demonstrate on the first joint of the day so you can see what ready looks like.

Click to enlarge

Perps before beds

This is a rule every bricklaying guide gives and every beginner gets wrong. Joint the vertical perpend joints first (the short cross joints between bricks), then the horizontal bed joints (the long runs).

The reason is mechanical. When you draw the jointer along a bed joint, it passes over the perps. If the perps are already tooled, the jointer rides smoothly past. If the perps are still raw, the jointer drags fresh mortar sideways out of them and into the bed joint, and you spend twice as long tidying up. Perps first, beds second. The pros call this sequence "perps, beds, then marriage" where the marriage strokes finish the junctions at top and tail.

Apply firm even pressure. The jointer should compact the mortar rather than ride across the top. A properly compacted joint sheds water for decades. A lightly dragged one will crumble within five winters.

The soft brush, immediately

Jointing leaves crumbs and small mortar blobs on the brick face. Deal with them straight away.

Use a soft-bristled brush (a dry 2 or 3 inch paintbrush works, or a dedicated churn brush from a tool merchant) and flick the crumbs off the face with light strokes. Do it within a few minutes of tooling the joint. Leave it and the crumbs cure onto the face. Scrub hard and you drag smeared mortar across the bricks, which is worse than the crumbs were.

For larger blobs that have already stuck, wait at least twelve hours before attempting removal. Trying to chisel or scrape fresh smears off just drags cement film across the face permanently. After twelve hours, blobs pop off cleanly with a dry churn brush or a plastic scraper. If the smears have actually cured onto the brick face, you're into acid-based brick cleaner territory, and that's a weekend job you don't want.

Skate, sled runner, or barrel jointer

Three tool formats cover the market. The difference matters for how the finished joints look, not for which profile they produce.

Skate jointer. The basic tool. A short cranked steel bar, usually double-ended with two sizes, held directly in the hand. Cheapest, most common, and what most UK bricklayers carry. Gives a perfectly acceptable finish on short runs. On long continuous bed joints, the short tool length makes it harder to keep pressure absolutely consistent, so you can see faint ripples where one stroke ends and the next begins if you look closely.

Sled runner. A longer jointer, typically with a wooden handle at one end, used for long straight bed joints. The extended length evens out hand pressure variations, giving a more uniform finish on long runs. Rare at UK retailers but popular with professional bricklayers who joint long gable walls. Worth considering if the extension has long uninterrupted elevations.

Barrel jointer set. Multiple barrels of different sizes that slot into a single handle, letting you swap between 10mm, 13mm, and 16mm profiles without changing tools. Marshalltown's QLT barrel jointer at Screwfix runs around £26. Useful if you're jointing a mix of brick and block, less essential for a single-material extension.

For one extension on a standard UK brick skin, a skate jointer is all you need. The Marshalltown M83 at Toolstation or Amazon is the standard answer for most extensions. If you've got specific reasons to want a smoother finish on long runs, a sled runner justifies the extra £10 – £15.

What to buy

The good news: this is one of the cheapest tools on any UK site. Even the barrel sets stay in two-figure territory, and the standard professional skate jointer sits in single figures.

The jointer is a tool you will almost certainly use once and then keep for occasional future patching. Don't stretch to the barrel set at £26 unless the versatility genuinely earns it. A Marshalltown M83 at £9 – £10 is the answer for around 80% of homeowners.

The site brickie's alkathene trick

Every bricklaying forum on the UK internet eventually mentions the same thing: a short length of alkathene pipe (the blue plastic water pipe used for mains supply) produces a near-identical bucket handle profile to a proper jointer. Cut a 150mm length, and drag it along the joint. Every UK site has offcuts lying around and they cost nothing.

For a professional doing hundreds of joints a day, the dedicated tool gives cleaner consistency and less hand strain. For a homeowner finishing a small patch or matching a garden wall, the pipe trick works. Don't build your extension with it, but don't dismiss it either.

Lime mortar, heritage properties, and when a jointer is the wrong tool

Pre-1920s properties were built with lime mortar, not Portland cement. Lime is softer than brick. Cement is harder. Applying cement mortar to a Victorian or earlier property forces moisture through the brick face instead of evaporating through the joint, and the brick faces spall off within a few winters. This damage is irreversible.

For lime mortar pointing, the timing is different (mortar can take over an hour to reach thumbprint-hard, sometimes requires an intermediate wood-finish stage, followed by a churn brush) and the tool surface matters. Faithfull Prestige and CO.ME (Italian-made, wooden handled) jointers are recommended specifically for lime work because their polished steel doesn't drag the softer mortar.

If you're extending onto a pre-1920s property, the existing mortar is almost certainly lime. Get a heritage-experienced bricklayer, not a general builder. The jointer is the easy bit. The mortar matching and timing is the skill.

Where you'll need this

Brick jointers appear wherever fresh mortar needs finishing on any extension or renovation project:

• Walls and blockwork - finishing mortar joints on new brick and block courses as the wall goes up
• Foundations and footings - jointing visible blockwork above ground level on exposed foundations
• Snagging checklist - identifying missed joints, inconsistent profiles, and mortar smears before sign-off