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Red rubber brick — also called rubbed brick or gauged brick — is a fine, soft, sand-rich brick fired at a lower temperature than ordinary stock or facing brick, then cut and rubbed by hand to precise dimensions using saws and abrasive stone. The name has nothing to do with rubber as a material; it refers to the rubbing process itself. Where London stock brick was built for volume — walls, whole facades, the fabric of the city — red rubber brick was built for precision: the gauged arches over Georgian windows, the fine flush joints of a doorcase, the decorative brickwork that signalled a building was better specified than its neighbours.
You'll find it concentrated on Georgian townhouses across London, particularly around door and window openings, and again in the late Victorian Queen Anne Revival style, when architects like Norman Shaw revived gauged red brick detailing as a deliberate historical reference. Much of the material historically came from Kent's brickworks, fired from the county's fine clay and barged up the Thames.
What makes gauged brickwork distinctive
A gauged arch — the curved brick arch you see over many Georgian windows and doors — is built from wedge-shaped rubbed bricks, each one cut and rubbed to an exact taper so the joints between them are as fine as one or two millimetres, laid in lime putty rather than an ordinary bedding mortar. The precision is the entire point: a gauged arch reads as a single sculpted curve rather than a series of visible bricks, and achieving that took a skilled mason working the brick by hand, not a standard bricklaying process.
This same fine, hand-worked brick appears in flush-jointed facing panels, decorative string courses, and door surrounds — anywhere a building's specification called for refinement rather than economy.
Why it needs gentler treatment than stock brick
The qualities that make red rubber brick easy to cut and rub precisely — a fine, sand-rich, relatively soft body — are the same qualities that make it far more vulnerable than ordinary London stock brick to an aggressive cleaning method. Pressure washing erodes rubbed brick quickly, rounding off the crisp arrises that were the entire point of the rubbing process. Abrasive blasting removes the finished surface almost immediately, along with any tool marks or fine detail. Acid, as with any calcium-bearing masonry, attacks the brick chemically as well as the lime mortar around it.
We treat red rubber brick as closer in fragility to Bath stone than to the London stock brick that usually surrounds it on the same facade — which means the same building can genuinely need two different specifications side by side: DOFF at standard settings for the stock brick field, and a gentler DOFF setting or poultice cleaning for the rubbed brick arch and dressings around the openings.
Staining and cleaning
Localised staining — iron run-off from fixings, soot deposition around chimney breasts, biological growth in sheltered arches — is common on rubbed brick given its age and its typically sheltered position around doors and windows. Poultice cleaning is our usual method here, for the same reason it's often preferred on Bath stone: it draws the stain out without introducing mechanical or thermal stress to a surface that can't absorb much of either.
Where general atmospheric soiling needs addressing across a wider area of rubbed brick, DOFF steam at a reduced setting is appropriate, calibrated specifically to the material rather than the standard setting used on the stock brick field nearby.
Repointing gauged brickwork
The fine joints in gauged brickwork — often no more than a millimetre or two — were traditionally laid in lime putty, not the wider lime mortar used for ordinary brick coursing. Repointing rubbed brickwork to anything like its original appearance requires matching that joint width and the lime putty specification, not simply using the same mortar mix as the rest of the facade. Cement pointing on gauged brick is particularly damaging — the hard, wide joint destroys the crisp, almost joint-free appearance the original brickwork was built to achieve, quite apart from the moisture-trapping problems cement causes on any historic masonry.