It's a common sight in older gardens around Pershore, a patio that once sat flat now has dips, wobbly slabs or pooling water after rain. Understanding what causes this helps explain why proper groundwork matters so much more than the paving material chosen on top of it.
The usual culprits
The most common cause is an inadequate sub-base, either too shallow or not compacted properly during installation, which allows the ground underneath to shift under weight and weather over time. Poor drainage is a close second, water that isn't shed away from the patio can wash out bedding material beneath individual slabs, causing them to rock or sink in isolated spots rather than uniformly across the whole area. Tree roots growing beneath a patio, and ground that simply wasn't compacted well before laying, are also frequent causes in older gardens.
Frost can make an already marginal sub-base worse, as repeated freezing and thawing of trapped moisture gradually loosens bedding material. This is particularly relevant on the heavier clay soils found in parts of Worcestershire, which hold water and expand and contract more than free-draining ground, putting extra strain on a patio's foundations over successive winters.
What can be done about it
A few isolated sinking slabs can often be lifted, the bedding built back up, and relaid without disturbing the rest of the patio. Widespread unevenness, however, usually points to a sub-base problem across the whole area, and in that case patching individual slabs is only ever a temporary fix. It's worth having a contractor assess whether the issue is localised or systemic before spending money on repairs that won't hold.
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