Patios and paths pulling away from the house wall

Why the gap opens between paving and brickwork

A patio slab sits on compacted ground. The house wall sits on foundations dug well below that surface layer. Because they rest on different things, they move at different rates.

In warm weather the topsoil dries out and shrinks. The shallow paving drops with it. The deeper foundations stay where they are because the moisture change does not reach them. So a gap appears along the line where the concrete meets the bricks.

Rain reverses the process. Water soaks back into the soil, the clay swells, and the paving rises again. The gap narrows or closes entirely. This seasonal opening and shutting is normal for most homes in Kent, especially those built on Weald Clay or Gault Clay.

A hairline space that comes and goes with the weather is rarely a problem on its own. It becomes worth watching when the gap stays open through winter, or when it gets wider each summer instead of returning to the same width.

When a path moving points to the house moving too

Paving dropping away from the wall does not automatically mean the house is sinking. But sometimes both are happening together.

If the ground under the footings is losing volume, the wall will settle as well as the path. Look for other signs inside. Doors that used to latch easily now need lifting. Plaster cracks run diagonally from window corners. Skirting boards separate from the floor along one side of a room.

Outside, check whether the gap is even all the way along. A uniform space suggests general shrinkage. A gap that tapers, wide at one end and tight at the other, suggests the wall itself is tilting. That tilt matters more than the patio movement.

A specialist conducting a structural movement survey measures these angles precisely. They record the direction of lean, compare it to previous readings if any exist, and determine whether the house wall is moving independently of the path or being pulled by the same ground loss.

Drains running under the patio edge

Many older homes in Kent have drainage pipes buried just outside the footprint of the house, often running parallel to the back wall beneath the patio. These pipes carry rainwater from downpipes or waste from kitchens and bathrooms.

If a joint fails or a pipe fractures, water leaks into the soil directly beside the foundations. Over months this washes fine particles away, leaving voids. The ground above settles into those voids, and the paving drops first because it has the shallowest base.

The leaking water can also soften the clay supporting the house wall. So the path moves, then the wall follows. A drainage CCTV survey lets a specialist see the condition of underground pipes without digging up the garden. They feed a camera along the run and record where water is escaping.

Fixing a broken drain early stops the soil washing away further. Leaving it allows the void to grow until the settlement reaches the deeper footings.

Trees drawing moisture from under the slabs

Roots follow water. A tree planted near a patio will send fine roots into the soil beneath the paving because that top layer holds moisture after rain. In dry spells those roots keep extracting water, drying the clay faster than open ground would lose it.

The effect shows up first at the edge nearest the tree. The gap there widens while the far end stays tight. Shrubs and hedges do the same thing on a smaller scale. Even a mature boundary hedge can pull enough moisture from the subsoil to cause localised shrinkage.

Removing the plant suddenly can cause a different problem. Without roots taking water, the clay rehydrates and swells, pushing the paving upward. A specialist usually advises managing the vegetation gradually rather than clearing it all at once, so the ground adjusts slowly.

What to measure before calling anyone

Take a photograph of the widest part of the gap with a coin or ruler laid across it for scale. Note the date. Do this every few weeks through the spring and summer.

These images give a specialist something concrete to work from. A single measurement tells them very little because they cannot see whether the gap is growing, shrinking or holding steady. A series taken over weeks shows the direction of travel.

Also note whether the gap is filled with debris, sand or old mortar. If it was previously sealed and the sealant has torn, the movement happened after the sealing work was done. That timing helps narrow down the cause.

Crack monitoring devices can be fitted later if a survey indicates the movement is ongoing. For now, photographs and dates are enough to start a conversation about whether the gap needs professional attention or simply seasonal watching.