What happens to clay dug from a London building site

If you are clearing a site in London and clay is coming out of the ground, you have a set of practical questions about what to do with it. This is a short FAQ that answers them plainly and points you onward for the detail. For how the wider picture fits together, see our working guide to clay from London construction sites. The answers below are about the common case: clean, naturally occurring subsoil and clay, not contaminated material.

What happens to clay dug from a London building site right now?

On most sites it is treated as something to move on rather than something to use. Once it is out of the ground it tends to be classified, loaded out, and hauled off site, and the transport, and the fee the landfill charges to take it, are real costs. There can be landfill tax on top of that, and how much depends on what the material is, which is the next question.

Do you have to pay to send it to landfill?

If it goes to landfill, then on top of the transport and the landfill’s fee there is landfill tax. From 1 April 2026, clean, naturally occurring subsoil and clay usually count as inert and are taxed at the lower rate of GBP 8.65 per tonne, while contaminated or mixed waste attracts the standard rate of GBP 130.75 per tonne. Reuse under the code of practice described below avoids the landfill route, and that tax with it. Whether reuse is open to you depends on the material and your site.

Can excavated London clay be reused?

Often, yes. A lot of clean excavated material never reaches landfill at all, because it can be reused under the development industry’s code of practice for excavated soil (the CL:AIRE Definition of Waste: Development Industry Code of Practice). Clean, naturally occurring clay is usually a good candidate for that route. You remain the waste producer and the duty-of-care holder throughout, so the decision to reuse rather than dispose sits with you and your advisers, not with whoever takes the material. The reuse route is covered in more depth in our working guide to clay from London construction sites.

Is the clay any good for anything?

Some of it may be. We dug clay from a Park Royal construction site and fired it across a range of temperatures, and so far the results are encouraging for that one clay. We have written up whether it is good for ceramics in a separate note on whether London clay is any good for pottery, and the measured numbers are on the Park Royal clay findings page. That said, this is one clay, one processing run, and one firing schedule. Another London clay might behave nothing like it, so we would not assume your material is good for anything until it has been tested.

Is there an alternative to sending it away?

For a small, documented quantity, yes. One option is to give a sample of clean, naturally occurring clay to a material studio that will test it and publish what it finds. That is what we do. It is not a disposal route and it does not take volume off your hands. What working together actually involves, and what we would test the clay for, is set out in our note on clay out of a London site, and the practical side is on the work with us page.

What are the rules?

The short version is that you keep the duty of care. You remain the waste producer and stay responsible for the material until it is lawfully disposed of or reused, whoever ends up handling it. The reuse route runs through the code of practice named above, and clean, naturally occurring clay is usually the easiest case to make. None of that removes the need to take proper advice for your own site.

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.