Why patio slabs sink and rock
A slab that rocks has lost the support underneath it. The usual causes are a thin or missing sub-base, slabs laid on dabs of mortar rather than a full bed, and water that has softened the ground below over the years. On older patios, tree roots and buried rubble settling unevenly are also common.
The pattern of the damage tells you a lot. A single loose slab near a door is often local wear. A dip in the middle of the patio, or a row of slabs that have dropped along the house wall, points to the base itself.
Patio repair: resetting a few slabs
Where the problem is limited, a patio repair is the sensible first step. We lift the loose slabs, clear out the old bed, check and firm the ground beneath, then lay a fresh bed and set the slab back to the level of its neighbours. The joints around it are repointed so it matches the rest of the patio.
If, once the slabs are up, the ground underneath turns out to be soft or wet across a wider area, a repair will not hold for long. We will show you what we find and explain the options before going further.
How relaying a patio works
Relaying follows a clear order of work:
- Slabs lifted carefully and stacked, with any broken ones set aside
- The old bed and failed base dug out to firm ground
- A new sub-base laid and compacted in layers, shaped to fall away from the house
- Drainage added where the ground holds water, such as a channel along the house wall
- Slabs cleaned, laid on a full bed and jointed
Patios
- Natural stone and porcelain options
- Careful levels and drainage
- Neat edges and lasting foundations
The flagstone project on our homepage
The before and after project of old flagstones lifted and replaced on our homepage shows this kind of job. Tired, uneven flagstones were lifted, the ground prepared, and fresh paving laid with a proper drainage channel against the house. It is a good example of a patio where the fault was underneath rather than in the slabs.
Reusing your old slabs
Natural stone flags and good quality slabs can often be cleaned and relaid, which keeps the character of an older patio. Mortar stuck to the back of each slab has to be cleaned off so it sits flat on the new bed. Some slabs always crack on lifting, so it is worth checking whether matching replacements are available, or planning to use the broken pieces around the edges.
If the slabs are thin, badly stained or very worn, relaying is a natural moment to change the stone. Our guide comparing porcelain and sandstone covers that choice.
Repair, relay or clean and repoint?
There are three levels of patio work. Cleaning and repointing deal with a patio that is sound but tired. A repair resets a few loose slabs. A relay rebuilds the base under the whole patio. On the visit we lift a slab or two where needed, so the advice is based on what is actually under your patio rather than what it looks like from above.
Investigate a sunken patio corner separately
A sunken patio concentrated in one corner needs a closer look at that location. Water arriving from another surface, disturbed soil near a former trench or an unsupported edge can produce a local dip while the rest stays stable. Note when the change appeared and whether it grows after rain. The pattern helps decide where investigation should begin.
Loose patio slabs are not always evidence that every flag must come up. Where adjacent paving remains stable, lifting the affected pieces can reveal the condition of their bedding and foundation. If the underlying weakness extends beyond the visible dip, the repair boundary may need widening. Agree that possibility before work rather than expecting a surface patch to correct a larger ground problem.
Need it sorted? Book patios
Describe the area that moves or holds water, and ask Ashley to assess the paving before deciding between a repair and a wider relay.