If you dig clay out of a London site, here is what could happen to it next.

On most London sites, excavated clay is something you have to deal with, and dealing with it costs money. It is dug, classified, loaded onto a lorry, and driven away, and the haulage and the gate fee at the other end are real. The landfill tax on top depends on what the material is. Clean, naturally occurring subsoil and clay usually count as inert, and from 1 April 2026 inert material is taxed at the lower landfill rate of GBP 8.65 per tonne, not the standard GBP 130.75 that contaminated or mixed waste attracts. Cleaner still, a lot of this material never reaches landfill at all, because it can be reused under the development industry’s code of practice for excavated soil. Either way it is treated as something to move on rather than something to use.

We work the other way around. The first question we ask of a material is not how to dispose of it, but whether it could become something. Our first project began with clay dug out of a Park Royal construction site, and the firing tests so far are encouraging enough that we want to see what other London clays do.

This note is for developers and landowners who have clay coming out of the ground and are curious what a material practice would do with it. It is plain on purpose, and it is honest about how early and how small we are.

What we would test it for

When clay reaches us we treat it as an unknown and work through the same basic questions we worked through with the Park Royal clay.

• How it behaves when it is processed: broken down, slaked in water, sieved, and dried back to a workable state.
• How it fires across a range of temperatures, and where it matures. The Park Royal clay reached its tightest, least porous state near 1050 C, at about 0.7 percent water absorption, then bloated and over-fired above that. Each clay has its own range.
• Whether it can be cast, thrown, or pressed, and what it takes to get there. The Park Royal clay would not slip-cast as it came; adding 2.5 percent barium carbonate made it castable. That was one clay. Another might behave nothing like it.
• Whether it could go into unfired building material rather than fired ceramics.

None of this is a promise about your clay. It is the list of things we would actually look at, and the results, good or bad, would be written up in the open the way the Park Royal results were.

What working together actually involves

The hard part is rarely the clay. It is the paperwork and the uncertainty around handing material to someone else. So here is the shape of it, plainly.

We understand the framework the development industry already uses for excavated material, and we keep what we do legal. We take clean, uncontaminated, naturally occurring London clay only, in small documented quantities, the kind of amounts a studio can process by hand rather than a spoil heap. We do not ask you to test anything new; if you already hold the chemical data for that stratum from your site investigation, a copy is enough for us to see whether it is clean.

What we are not: we are not a disposal service, we are not a waste facility, and we cannot guarantee a route off your site. No payment is implied in either direction. You remain the producer of the material and responsible for it, and the simplest arrangement is usually that the material is delivered to us as a documented destination rather than collected.

If you want the longer version, with how the rules fit and what to send, it is set out on the work-with-us page.

Honest about the stage we are at

This is early. It is one studio, working through a small number of materials a year, by hand, in Park Royal. We are not claiming to solve construction waste or to take volume off anyone’s hands. What we can offer is genuine interest in your material, careful testing, and results published in the open so that whatever we learn is useful beyond this one studio.

The reason proximity matters is simple. Park Royal is one of the largest industrial estates in Europe, with thousands of businesses within walking distance. Clay dug in west London tested and used in west London avoids most of the transport that makes low-impact materials stop being low-impact.

Open questions

• Do other London clays behave like the Park Royal clay, or is each one its own problem?
• What is the smallest, lowest-friction way for a developer to move a documented sample to us without it becoming a burden?
• At what point, if any, does interest like this become worth a developer factoring into how a site is dug, rather than only how it is cleared?

If your site is producing clay and you are curious, tell us about your waste streams. A short email describing the material, the rough volume, the site location, and your timeline is plenty to start. The soft version of the ask is the honest one: we would rather hear about it than not.

This is general information, not legal or regulatory advice. You remain the waste producer and the duty-of-care holder for your material, and should take advice from your own environmental consultant, a CL:AIRE Qualified Person, or the Environment Agency before classifying or moving anything.