Why does paving sink on Dutch soil — and how do you fix it?

• No or thin foundation — the main culprit in DIY patios: tiles on garden soil or 5 cm of loose sand.
• Shrink–swell clay: heavy clay moves centimetres between dry and wet seasons.
• Utility trenches: poorly compacted backfill above cables and sewers settles for years — recognisable as a straight sunken line.
• Washout: a leaking downpipe or missing fall erodes the sand bed locally.
• Ants and moles: sand heaps between the joints give them away.

1. Lift the tiles well beyond the sunken area (30 cm margin).
2. Remove the cause: fix the leak, compact the trench, treat the nest.
3. Build the missing foundation: 15–20 cm crushed hardcore, plate-compacted in layers.
4. Screed a 3–5 cm sand/grit bed to a fall of 1–2 cm per metre, away from the house.
5. Re-lay, compact and re-sand the joints.

Cost 2026: re-laying with your existing tiles runs €30–€60 per m² including the new foundation — a 30 m² patio lands at €900–€1,800, far cheaper than new materials.

• Invest underground: 15–20 cm of compacted hardcore is the difference between 3 and 20 years of staying level.
• Water management: correct falls and permeable joints — standing water softens the base.
• Edge restraints set in concrete stop sideways creep.
• Break up large areas with bands or borders so the clay can move without cracking lines.
• Keep heavy paving a metre from young trees — roots lift tiles.