Colliery Made Ground in the Wakefield District

What made ground actually is

Made ground is any material placed by people rather than laid down naturally. Across this district that means backfilled opencast workings, colliery spoil and waste tips, infilled quarries and clay pits, levelled industrial land, and the ordinary accumulated fill of a century and a half of industry.

The defining property is variability. Composition and compaction change across a single plot, sometimes dramatically, because nobody placing it was engineering a foundation - they were disposing of material. Two trial pits ten metres apart can find quite different things.

Why it is a foundation problem, not a subsidence problem

This distinction matters and it is regularly muddled. A void beneath a building - a shallow working, a shaft - is a subsidence question: something may collapse. Made ground is a bearing and settlement question: the material consolidates unevenly under load.

That difference changes everything downstream. Different investigation, different remedy, different insurance position, and a different conversation with Building Control. A site can of course have both, which is precisely why they should be assessed as two questions rather than one.

Made ground also settles for a long time. Fill placed decades ago may still be consolidating, particularly where it was tipped rather than engineered and where water can move through it.

How it is investigated

Proportionate to what is being built, in a sequence where each stage justifies the next:

• Desk study first - historic Ordnance Survey mapping is unusually powerful here, because it shows what was on the site before the houses were: a tip, a pit, a quarry, a colliery yard
• Geological mapping and the mining record, which establish the other half of the picture
• Trial pits to see the material, its depth and what lies beneath it
• Boreholes and probing where the fill is deep or the loads are significant
• Laboratory testing to characterise the material properly, including its chemistry where contamination or aggressive ground conditions are a possibility
• Only then, foundation design - to what has actually been found rather than to a standard detail

What the foundation options look like

There is no single answer, and that is the point. Depending on the depth and consistency of the fill and the loads involved, the design may dig through the made ground to a competent stratum, use a reinforced raft to span variability, pile through it, or - where the fill is shallow and consistent - treat or remove and replace it.

What does not work is a standard strip footing designed on an assumption. The most expensive outcome we see on this ground is foundations designed before anybody looked, then revisited once the trenches are open and the programme is already running.

If you already own a house on it

Do not assume the worst. Very large numbers of properties across this district sit on or near made ground and perform perfectly well, and much of the settlement associated with it happened long ago.

Where cracking has appeared, an engineer's job is to work out whether the ground is actually involved. In this district it very often is not: wall tie corrosion in the interwar and post-war cavity stock, failed lintels, thermal movement, unsupported chimney breast removals and leaking drains account for the majority of what we investigate.

A structural survey and report is a fixed £580 + VAT with the report inside 10 working days of the inspection, guaranteed. Trial pits, monitoring and ground investigation are scoped separately and only recommended with a reason attached.