How to Lay a Patio
Last updated: 30 September 2026
Dig the area, lay a hardcore sub-base, apply a mortar bed, lay the slabs with spacers, and fill the joints with sand.
Overview
Laying a patio is a popular garden improvement project. This guide covers preparing the ground and laying paving slabs correctly.
Step-by-Step Fix
Before beginning any repair, ensure you have isolated power or water supplies. Clear your workspace, gather standard hand tools, and wear appropriate personal protective equipment (PPE).
- Mark out the patio area using string and pegs. Use a spirit level to check that the ground is level. Decide on the size and shape of the patio and mark it clearly. Allow for a slight slope away from the house for drainage.
- Dig out the area to a depth of about one hundred and fifty millimetres. Remove all grass, soil, and roots. Compact the ground using a plate compactor or hand tamper. This provides a stable base for the patio.
- Lay a sub-base of hardcore or crushed stone to a depth of about one hundred millimetres. Compact it thoroughly in layers using a plate compactor. Check the level regularly with a spirit level. This sub-base prevents the patio from sinking.
- Cover the hardcore with a layer of sharp sand about thirty to forty millimetres deep. Compact it and level it using a screed board. This provides a smooth bed for the mortar. Check that the sand is level and consistent in depth.
- Mix a mortar bed using sharp sand and cement in a ratio of four to one. Add water to achieve a stiff consistency. Apply the mortar over the sand in small sections working from one corner. Use a trowel to spread it evenly.
- Lay the first paving slab in position. Press it down firmly into the mortar. Use a rubber mallet to tap it level. Check with a spirit level. Use plastic spacers between slabs to maintain consistent joint widths of about ten millimetres.
- Continue laying slabs working from the first slab outward. Check the level of each slab as you go. Use a straight edge to ensure adjacent slabs are level with each other. Cut slabs with an angle grinder or bolster chisel where necessary to fit edges.
- Once all slabs are laid allow the mortar to cure for twenty four to forty eight hours. Do not walk on the patio during this time. After curing fill the joints with kiln dried sand or polymeric sand. Brush the sand into the joints and compact it.
- Wet the joints with a fine spray to settle the sand. Repeat until the joints are completely full. Polymeric sand hardens when wet and prevents weeds from growing between the slabs. It also locks the slabs in place.
- Inspect the finished patio for any uneven slabs or gaps. Tidy up the edges and remove any excess sand. If you are unsure about any step or the area is large and complex consider hiring a professional landscaper.
Common Symptoms & Diagnostic Resolutions
Review the common error codes and operating symptoms below to quickly identify the root cause of the fault before ordering replacement parts.
| Symptom / Code | Likely Root Cause | Recommended Resolution |
|---|---|---|
| Slabs become uneven | Subsidence or poor compaction of the sub-base | Lift the affected slabs, recompact the sub-base, and relay the slabs on a fresh mortar bed. |
| Slabs crack | Incorrect thickness or base movement | Use thicker slabs of at least fifty millimetres and ensure the sub-base is well compacted. |
| Weeds growing between slabs | Joints not properly filled | Fill the joints with polymeric sand which hardens when wet and prevents weed growth. |
| Water pooling on patio | Insufficient slope for drainage | Ensure the patio slopes away from the house at a gradient of about one in eighty. Relay slabs if necessary. |
Frequently Asked Questions
How thick should paving slabs be for a patio?
Use slabs at least fifty millimetres thick for a patio. Thinner slabs are suitable for pathways only. Thicker slabs resist cracking and movement better.
What is the best sub-base for a patio?
Hardcore or crushed stone compacted in layers is the best sub-base. It provides a stable foundation and prevents the patio from sinking or becoming uneven over time.
Can I lay a patio on grass?
No you must remove the grass and soil first. Laying a patio on grass will result in an uneven surface and the patio will sink. Excavate to the correct depth and lay a proper sub-base.
How long does it take to lay a patio?
A small patio of about ten square metres takes two to three days for a competent DIYer. Larger patios take longer. Allow additional time for the mortar to cure before walking on the surface.