Getting your paving level and firm again

Most patios and paths get years of feet, furniture and weather.

Now and then a slab starts to rock, or one corner sits a little lower than its neighbours.

These notes explain why that happens and how a paved area is put right. They draw on guidance from Interpave, the paving trade body, and from GOV.UK and the Health and Safety Executive (HSE).

Why a slab starts to move

Each slab sits on a bed of sand or mortar. That bed gives the slab even support across its whole underside. Under the bed is a layer of compacted stone called the sub-base.

Interpave explains that good compaction of these lower layers is what stops slabs rocking or forming trips. Water getting through the surface can also weaken the layers underneath.

Putting a slab back level

GOV.UK guidance on driveways says any areas that seem softer than the rest should be dug out and refilled with sub-base. The new sub-base is then compacted to give a firm foundation.

The slab then goes back on a fresh bed. Interpave says a mortar bed is enough for areas used mainly on foot. Areas that cars drive over regularly need slabs bedded on sand, with sand in the joints.

When paving is first laid, Interpave's tolerance is that neighbouring slabs differ in level by no more than 3 mm. A slight fall across the surface lets rain run off. Interpave recommends a cross fall of at least 1 in 40 where possible.

Fitting a replacement slab

Sometimes a slab is cracked and a new one has to be cut to fit. Cutting concrete paving with a power saw can make a lot of dust that contains silica.

The HSE suggests a few ways to keep that dust down.

Use a block splitter instead of a saw where you can.
Plan the layout to need fewer cuts.
Have slabs cut off site and delivered.
If a saw is needed, use one with a water attachment and wear a close-fitting FFP3 mask.

Keeping the surface and joints in good order

Regular brushing keeps most paving looking well. If the colour starts to look dull, Interpave suggests scrubbing with soap and warm water and rinsing it all away afterwards.

A power hose can wash sand or mortar out of the joints. Interpave advises checking the joints afterwards and topping them up where needed. Moss and algae tend to grow where paving is shaded, under trees or poorly drained. Try any cleaner on a small hidden patch first.

Relaying a front garden

Some people take the chance to relay a whole front garden or drive. In England, the Planning Portal explains that a new or replacement driveway of any size does not need planning permission if it lets water drain through. Directing rainwater onto a lawn or border also counts.

Laying a hard surface that does not drain over more than five square metres of front garden needs planning permission.

The pavement outside your home

The public pavement is usually not yours to mend. GOV.UK says most councils maintain most pavements, including replacing broken or missing slabs. In England and Wales you can find your council and report a problem through GOV.UK.

Choosing someone to do the work

Citizens Advice suggests getting quotes before you choose a trader, checking insurance and agreeing a written contract before work starts. GOV.UK's paving guidance advises using an experienced landscape or driveway contractor. It also advises against casual contractors who knock on your door offering to lay a drive.