What's my stone, or my brick?
Four questions about where it sits, what colour it is, and what kind of building it's on. Not a lab test — a starting point, built from twenty-five years of looking at the same handful of materials across London's period buildings.
Where on the building is it?
What colour is it, and what kind of building is it on?
What colour is the brick?
This is very likely Portland stone
Portland stone is the pale grey-white limestone behind most of London's grand civic and commercial architecture — banks, war memorials, interwar headquarters, and the dressings on countless Victorian buildings. Look closely at a clean patch and you may see small shell fragments in the surface; it's a shelly, oolitic limestone, quarried on the Isle of Portland since the seventeenth century. Left uncleaned in a polluted city, it blackens with a sulphate-rich atmospheric crust rather than simple dirt, which is why it often looks far older and dirtier than it actually is.
This is very likely Bath stone
Bath stone is Portland's warmer, softer relative: a honey-to-cream coloured limestone, more porous and more easily worked, which is why it turns up so often on Georgian porticos, door surrounds, and decorative dressings rather than load-bearing ashlar. Its softness cuts both ways — it takes fine detail beautifully, and it's also more vulnerable to the wrong cleaning method than Portland stone is.
Probably Portland or Bath stone — here's how to tell them apart
Both are limestones used constantly across London, and from a distance they can look similar. The tell is usually colour and context: Portland stone is cooler, closer to grey or off-white, and tends to carry small shell fragments visible up close; it's the stone of civic and commercial buildings. Bath stone is warmer and more honey-toned, softer and more porous, and shows up far more often on Georgian porticos and decorative dressings than on a whole facade. If you're still not sure, that's exactly what a site visit is for — it costs nothing and settles it in minutes.
This is very likely York stone
In London, York stone almost never appears as facade walling — it's a sandstone used underfoot: steps, paving, sills, and copings. It's a brownish-grey to buff sandstone, laid in slabs rather than carved into ashlar blocks, and the wear pattern you're looking at — rounded edges, surface loss on the most-trodden sections — is a different maintenance problem to a soiled facade.
This is very likely London stock brick
London stock brick is the yellow-buff brick that defines whole streets of Victorian London. The colour comes from the London clay and the ash content in the original firing, and it varies from a pale straw colour to a darker grey-brown depending on the brickworks and the firing. It's softer and more porous than later machine-pressed red brick, which is exactly why it needs a gentler approach than a standard brick clean.
Likely a standard red or orange brick
Not every red brick in London is red rubber brick — most of what you'll see on Victorian and Edwardian terraces is an ordinary machine-pressed brick, laid in standard coursing rather than the fine gauged work around a door or window. It's generally more robust than stock brick or rubber brick, but the right cleaning approach still depends on its condition and what's actually on it, which is where a site visit earns its keep over a guess from a photo.
This is very likely red rubber brick
Red rubber brick is the fine, smooth, hand-worked brick behind London's Georgian gauged arches and doorcases — the crisp, finely-jointed brickwork curving over a door or window, rather than the ordinary brick of the wall around it. It was cut and rubbed to shape rather than moulded, which is exactly why it's finer-grained and more easily damaged by an aggressive clean than the brick either side of it.
This is very likely terracotta or faience
If it's glossy, moulded with crisp repeated detail, or an unusually uniform colour for natural stone or brick, you're likely looking at architectural terracotta or glazed faience — common on Victorian and Edwardian commercial buildings, often in deep red, buff, or cream. It's also the least forgiving material on this list to get wrong: the wrong method can blow the glaze or crack the moulded face in a way that can't be undone.
This is a starting point, not a survey. Lighting, paint, and previous repairs can all throw off an identification made from a description or a photo. If you want certainty, a site visit costs nothing and takes about twenty minutes.
Want the certain answer rather than the likely one? We'll come and look at the actual stone or brick in front of us, tell you what it is, and put a written specification together — free, and with no obligation.
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