After the hottest summer on record drove subsidence insurance payouts to an all-time high of £307 million, and with drought warnings already in place for 2026, structural movement is climbing the agenda for social landlords. Omar Alata, Head of Social Housing at ground engineering specialist Geobear, discusses procurement habits, and how Harrow Council saved nearly £500,000 on a single block.
Omar, subsidence has been in the news a lot over the past year. What’s actually going on?
The short version is weather. The driest spring in a century was followed by the hottest summer on record, and much of England – London, the South East, the Midlands – sits on shrinkable clay. When clay dries it contracts, foundations move, and you get the classic symptoms: stepped cracking, sticking doors, gaps at skirtings. Insurers paid out a record £300 million for residential subsidence in 2025, and the damage often shows up months after the heat, so cases are still landing now. With the Environment Agency warning that drought could carry into this summer, I’d expect another busy year.
Is social housing stock more exposed than private housing?
In many areas, yes. A lot of council stock went up quickly in the post-war and 1970s booms, on foundations shallower than today’s standards. Estates were also landscaped generously, with trees planted close to homes. Fifty years on, those trees are mature and their roots are drawing moisture from the clay right under the foundations – what the industry calls clay tree subsidence, and it accounts for a large share of claims in surge years. Redditch is a good example – Bromsgrove and Redditch Council manages over 6,000 homes, much of it 1970s stock with exactly that combination of shallow footings, clay and maturing trees.
The traditional answer is underpinning. What’s wrong with it?
Nothing, structurally – it works. The problem is everything around it. You’re excavating under a building, so tenants have to move out, often for 20 weeks or more. Someone has to find and fund temporary accommodation at around £4,000 a month per family room. You’ve got heavy plant on the estate for months, mud everywhere – and underpinning schemes usually mean cutting back vegetation and removing the very trees that make an estate worth living on. And the whole time, those homes are voids. The sector already has around 34,000 empty council homes in England, plus 55,000 housing association voids, against 1.34 million households on waiting lists. A repair that adds to the void count for five months is the wrong tool for the moment.
So what does Geobear do differently?
We improve the ground instead of rebuilding the foundation. We drill small holes through the foundations and inject an expanding geopolymer resin that targets the weakened soil directly. The majority of the work happens outside the building, with no excavation, and a typical property takes days rather than months. Tenants stay in their homes throughout and most tell us they barely noticed us. It cuts the other way too: where homes have already been voided by subsidence, we can have them back in letting condition within weeks, not months or years. The carbon footprint is around 70% lower than underpinning as well, independently verified.
Tell us about the Harrow project – the numbers there were striking.
That one showed what’s possible. Harrow Council had a 12-unit block moving on shrinking clay and had followed the standard route: investigation, engineer’s recommendation to underpin, tender. The price came back at £240,000 with 20 weeks on site, and every household – many elderly and disabled – facing relocation. We proposed the geopolymer alternative at £83,000, delivered in about ten days, nobody moving out.
The direct saving was 65%, but the indirect savings were just as big. Temporary accommodation alone for those households over 20 weeks would have been somewhere between £240,000 and £320,000, before void losses and weeks of officer time arranging a decant. All in, Harrow saved close to £500,000 on one block – money that went straight back into other maintenance projects. And honestly, the bit I’m proudest of is what didn’t happen: elderly residents weren’t moved away from family and carers for five months, and not a single tree around the block was removed. It was clay tree subsidence, but our approach treats the ground rather than punishing the trees – the green space the community actually uses was untouched.
Did anything need to change on the council side to make that happen?
Procurement, mainly. The tender was already running, so Harrow’s maintenance team had to make the case internally for departing from it – which they did, with the numbers to back it up. Credit to them; challenging an established process takes nerve. The knock-on is that Harrow is now re-evaluating other maintenance schemes through the same lens. Many procurement frameworks were written before methods like ours existed, and quietly lock in the most expensive, most disruptive option by default.
What are tenants and residents actually saying?
That’s been the most encouraging part. At Redditch, the council has had no complaints at all – if anything, tenants are pleased the council is visibly committing to fixing their homes. Penny Bevington, who leads the capital programme there, put it simply: they put tenants first, and rehoming people wasn’t a feasible option. That framing is spreading across the sector.
If a housing manager suspects subsidence in their stock, what should they do now – before summer?
Don’t wait for the cracks to get worse. Properties showing minor movement now will deteriorate if we get another dry summer, and early intervention is always cheaper. Get them surveyed, and before committing to underpinning – or decanting tenants – ask whether ground improvement is viable. In most clay cases it is. Every decant we avoid is a home that stays in use, and right now the sector can’t spare a single one.
Omar Alata is Head of Social Housing at Geobear. To discuss subsidence affecting your stock, please contact the company.
- 0800 084 3503
- www.geobear.com
- omar.alata(Replace this parenthesis with the @ sign)geobear.com