Made ground
Subsidence on made ground near the Hampshire coast
Homes built on reclaimed harbour edges, estuary silts and filled land need different repair methods. Find out why soft coastal ground changes what a specialist can use, and what that means for your house.
Why houses on reclaimed land crack near the water
A house built on reclaimed land cracks when the fill beneath it settles unevenly. Around the south Hampshire coast, from Portsmouth to Southampton and along the waterside towns, much of the ground was created by tipping material into former harbours, mudflats or marshes. That fill ground movement affects any property sitting on top of it.
Subsidence on made ground behaves differently from movement on natural soils. The material underneath might be loose rubble, old dock waste, silt dredged from an estuary, or earth pushed over a former creek. None of it was laid down with the weight of a house in mind. When a building sits on this kind of base, the pressure pushes the loose material sideways or compresses it further. Cracks appear where the walls have no support left.
If you are wondering whether your plot is built on made ground or fill, look at the history. Older maps often show former shorelines, docks or marshland where streets now stand. A specialist surveyor can confirm this by taking samples from below the foundations. They bore down through the layers to see what the house actually rests on, and how deep the solid geology lies.
Why resin injection rarely works on soft coastal ground
Resin injection strengthens soil by expanding within it, binding loose particles together. It works well under homes built on firm sands or gravels. But if your house stands on deep, soft fill near tidal water, there may not be enough stable material for the resin to grip. The liquid simply follows the path of least resistance through voids and loose silt.
This is why a specialist will often steer away from resin for coastal ground improvement on foundations resting on estuary deposits. The method needs a certain density in the soil to create a reliable platform. Where the ground is mostly uncompacted waste or waterlogged silt, injecting resin cannot produce a lasting result. The house continues to settle because the underlying problem remains untouched.
That does not mean resin has no place near the coast. It can still work on parts of a structure founded on firmer material, or where the fill layer is thin enough to bridge. A site investigation tells the specialist exactly where the boundary lies between usable ground and material too soft to treat this way.
Piling instead of traditional underpinning on fill
Traditional underpinning digs beneath existing foundations and pours concrete to deepen them. This approach assumes the soil just below the footing is strong enough to carry the new concrete base. On soft coastal ground in Hampshire, that assumption often fails. Digging into loose fill risks disturbing the very material holding the house up, and the new concrete pad may simply sink further.
So piling for soft ground in Hampshire becomes the preferred route. Screw piles or driven piles pass straight through the weak layers until they reach something firm: bedrock, dense gravel, or compacted clay far below. The load of the house transfers down the pile shaft rather than spreading across the surface. This bypasses the unreliable fill entirely.
How deep those piles need to go depends on the site. Near the Solent, firm strata can lie anywhere from three metres to more than ten metres down. A specialist determines this by driving test piles or examining borehole logs before committing to a design. Every location along the coast has its own profile, so depth varies even between neighbouring streets.
What ground improvement involves at your home
Ground improvement covers several techniques used to strengthen weak soil without always resorting to deep piling. Vibro-compaction uses a vibrating probe to shake loose fill into a denser state. Stone columns replace pockets of soft material with compacted aggregate pillars. Each method suits different types of fill and different depths.
The work does require access. Plant machinery needs to reach the perimeter of the house, and sometimes the area directly beside the walls. Gardens get disrupted while rigs move into position and operate. How long the ground stays dug up depends on the scale of the problem. A single corner might take a few days; a full perimeter scheme could run to several weeks.
Specialists plan the sequence to keep disruption contained. They work in sections so the house remains supported throughout. Once the ground treatment finishes, surfaces are reinstated. The goal is to leave the garden restored while ensuring the foundations sit on material that will not compress further under the weight of the building.
Insurance, selling and living near tidal water
Whether an insurer covers repairs when the fill under a house was never compacted properly depends on the policy wording. Most buildings insurance covers subsidence damage, but some exclude problems caused by inadequate original construction. If the fill was placed decades ago without proper compaction, the insurer might argue the defect existed before the policy started. Reading the specific terms matters here.
Being close to tidal water adds another variable. Groundwater levels rise and fall with the tides, washing fine particles out of loose fill over time. In dry summers, clay soils shrink, but on made ground the mechanism is different. Tidal flushing removes material gradually, leaving voids that eventually cause settlement. Movement near the coast does not follow the same seasonal pattern as inland clay shrinkage.
Once repaired correctly, a house on made ground does not automatically become harder to sell. Buyers and their surveyors want evidence that the right method was used for the ground conditions. Proper piling or ground improvement, documented by a structural engineer, gives future purchasers confidence that the problem has been addressed at its source rather than patched over.
Signs your home on filled ground might be moving
Loose fill compresses slowly, and the walls above it respond first. These signs do not prove subsidence, but they point to movement worth investigating on ground near the Hampshire coast.
- 1
Diagonal cracks at corners
Cracks running from window or door corners downward often show one part of the wall dropping faster than the rest on weak fill.
- 2
Floors sloping toward walls
A noticeable tilt across a room floor suggests the ground beneath that edge has compressed more than the centre.
- 3
Gaps under skirting boards
When the floor drops but the wall stays put, a gap opens along the bottom of the skirting board.
- 4
Doors catching on frames
Frames twist as walls shift. A door that suddenly sticks at the top or side hints at uneven settlement nearby.
Questions about made ground in Hampshire
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Answers to the things homeowners ask when their house sits on fill near the coast.
- Finding out if you are on fill
- Historic maps, local authority records and a specialist borehole survey reveal what lies beneath your foundations.
- Why resin may not suit
- Soft, waterlogged silt lacks the density resin needs to bind. Piles bypass weak layers instead.
- Depth of piles near the Solent
- Firm strata vary from three to over ten metres down. Test borings establish the exact depth required.
- Garden disruption during work
- Rigs need access along the walls. Work runs in sections, typically lasting days to a few weeks.
- Insurance on poorly compacted fill
- Coverage depends on policy wording. Some insurers exclude defects present before the policy began.
- Selling after repair
- Documented piling or ground improvement reassures buyers that the correct method addressed the cause.
Get help with movement on made ground
Send details about your home and a specialist will review the ground conditions. This does not commit you to any repair work or cost.
- No obligation
- Specialist review
- Local knowledge