Chalk ground
Chalk ground in summer and why it behaves unlike clay
Send the details of what you have noticed at your home and find out whether it points to movement. There is no fee for an enquiry and no obligation to proceed with any work.
Chalk does not shrink when it dries out
Clay loses moisture through the warm months and contracts, pulling the ground away from shallow foundations. Chalk works differently. It is a rigid rock made of calcium carbonate, riddled with tiny pores that hold water but do not collapse when that water drains away.
A house sitting on solid chalk will barely move between January and July. The soil volume stays almost constant regardless of rainfall. So if you live in a chalk area and notice a crack opening during a dry spell, seasonal shrinkage is unlikely to be the cause.
This distinction matters because the advice given for clay areas does not apply here. Restricting tree roots or altering garden watering habits will not stabilise a footing on chalk. The problem usually lies elsewhere, and finding it requires looking at the ground in a different way.
Where the real risks lie on chalk
Chalk dissolves slowly in slightly acidic rainwater. Over centuries this creates voids beneath the surface, some small enough to ignore and others large enough to swallow a garden wall. These features are known locally as dene holes or swallow holes.
Old quarry workings add another hazard. Parts of Kent were dug extensively for cement production, and records of every shaft do not survive. A house built over filled ground can settle suddenly when the fill compresses or washes into a cavity below.
Water running through chalk also finds weaknesses quickly. A leaking drain under the footings will carry fine material into the rock fractures, leaving a void where solid support used to be. Unlike clay, which swells and seals small leaks, chalk lets water pass straight through, taking the soil with it.
What cracks look like on chalk ground
Movement on clay tends to produce tapered cracks, wider at the top than the bottom, because one edge of the house sinks while the other stays put. On chalk the pattern is often less predictable.
A void forming under one corner causes sudden local settlement. The resulting crack may run diagonally across a window opening or step along mortar joints in a staircase pattern. Because the shift happens fast, plaster finishes crack cleanly rather than stretching.
Doors and windows might jam without warning. You may hear creaking in floorboards that previously sat flat. These signs point to something changing under the footing rather than the whole house drying out evenly. Photographing the damage now gives a specialist a fixed point to measure against later.
Finding the cause before deciding on repair
Guessing at the reason for movement wastes money. A structural movement survey establishes whether the house is still shifting or has already settled. The specialist takes level readings around the walls and compares them to identify which footing has dropped.
If a drain leak is suspected, a CCTV camera sent through the pipework will show fractures or displaced joints letting water escape into the subsoil. Fixing the pipe often stops further movement without any foundation work.
Where a void is confirmed, the repair depends on its depth and size. Resin injection fills shallow gaps by expanding a structural foam beneath the slab. Deeper problems may need screw piling, driving steel shafts past the weak zone into firmer rock below. Crack monitoring over several months tells the specialist whether the chosen method has arrested the movement.
Tell us what you have noticed at your home
Leave your details and describe the cracking or sticking doors. An adviser will read your account and explain what steps make sense next. There is no charge for the enquiry.
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