The (sustainable) brick that built London

Christian Hernandez
3 min readJun 7, 2024


A rabbit hole led me to discover that 5 million homes in the UK were unkowingly built using lower-embodied carbon bricks…in the early 1900s!

Never knew that a leftover brick would lead me down such a rabbit hole. Our neighbours added an extension to their flat which required our separating wall to be temporarily torn down and then rebuilt using the same bricks. Three leftover ones have been laying in my garden for a year… until I picked one up this weekend and read “London Brick” on it…

As I googled “London Brick” I would come to discover the London Brick Company and learn more than I ever expected to about different types of ancient clay.

Started in 1900, the London Brick Company would, by its own accord, be used to build over 5 million homes across the UK. For context, there are, today, 30m homes in the UK so alost 20% of all housing stock was built with these bricks. At it’s height, the company was producing over 40% of all bricks in the UK.

London Brick homes in London. The one on the right has been sandbalsted to the original colour

These bricks, also called Fletton bricks after the town where they were made, owe their uniqueness to history…way back history, going back to the Jurassic period. The Oxford Clay basin, as it is known, was is a Jurassic era maritime sedimentary rock formation with an extremely rich embedded carbon source (from all the dead giant things swimming in that ancient sea).

Through some experimentation it was discovered that this specific clay was quite special. And a century and a bit later it would seem (to me at least) even more special than initially thought given its climate impact:

“The advantages of this clay were numerous. It being oily or bituminous burnt with very little additional heat, clearly saving significant costs compared to traditional brick making, though London Stock Bricks, using ash, with bits of charcoal in, were able to self-fire to an extent”

“Self-fire” implies lower heat requirement, which implies lower fuel sources needed, which implies lower embodied carbon (the carbon associated with the “extraction, production, transport, and manufacturing — stages of a product’s life”).

Great, so what? Well assuming current impacts were similar in 1900, brick making kilns currently represent a staggering 2.7% of global emissions. Much of that comes from the firing of the bricks to “cook” them. Requiring less heat, therefore, would mean a lower carbon footprint per brick at a scale of 5m homes!

The average UK home uses 8,000 bricks. Those 5m homes built with lower carbon footprint London Bricks, therefore required 40 billion bricks. The CO2 content of a UK common brick has been calculated to 0.24 kg CO2/ kg and a UK common brick weighs 3kg, each brick therefore has 0.72 kg CO2. The average home would therefore have 5,760 kg CO2 and the 5 million homes mentioned above would have 29 million tonnes (or 29 megatonnes of CO2).

Without knowing the actual carbon savings of the London Brick I won’t attempt to calculate the mitigated carbon from this magical clay, but instead wanted to call to attention this obscure fact about this thriving city that I call home having been built, without many of us knowing it, from what many climate tech companies are now trying to scale: lower embodied carbon materials. What an amazing rabbit hole…

PS You can still buy London Brick for when you are remodelling or extending your home

PPS A separate post might be needed for me to rant about the short sighted financial regulation through which tearing down a building or home (with all of its embodied carbon) is VAT-free (20%) but retrofitting and modernising an existing building pays full VAT 🤦



Christian Hernandez

Partner at @2150-vc backing technologies that make our world more resilient and sustainable. Salvadoran-born Londoner. YGL of the @wef Father ^3