How do I lay a path or small patio?

Paving fails because of what is underneath it rather than the slabs themselves. Inadequate excavation and poorly compacted hardcore causes sinking and rocking within a year, and it cannot be corrected without lifting everything.

Safety

What you'll need

• Slabs
• Hardcore and sand
• Spade and rake
• Compactor plate (optional)
• Spirit level and string line (optional)
• Rubber mallet (optional)

Step by step

1. Check for buried services before digging.Cables, water and gas pipes. A detector, and caution near where services enter the house. This is the one step that can genuinely hurt you.
2. Excavate deep enough.Typically 150-200mm below the finished level for a path — slab thickness plus bedding plus at least 100mm of compacted sub-base. Under-excavating is the most common cause of failure.
3. Keep the finished level at least 150mm below any damp course.Paving above the damp course bridges it and causes damp inside the house. This is a serious and common mistake.
4. Lay and compact the sub-base in layers.Hardcore or MOT type 1, in layers no more than 100mm, each compacted properly. This layer does the structural work, not the slabs.
5. Set a fall away from the house.About 1 in 80 — roughly 12mm per metre. Use a string line and check constantly. Water pooling against a wall causes damp.
6. Lay slabs on a full mortar or sand bed, not on dabs.Five blobs of mortar under each slab leaves voids that collect water, freeze and crack the slab. A full bed supports it evenly.
7. Tap each slab down and check level as you go.A rubber mallet and a spirit level on every slab. Correcting one slab later means lifting the ones around it.
8. Point or brush the joints once laid.Jointing compound or a dry sand and cement mix brushed in and watered. Open joints let weeds through and let water under the slabs.

Tips

• Hire a compactor plate for a day. Hand compaction is not adequate for a sub-base and it is the difference between a path that lasts and one that sinks.
• Order about 10% more slabs than the area. Breakages happen and matching a batch later is difficult.
• For a large patio or anything near the house, consider whether the drainage and levels need professional input. Getting them wrong causes damp.

Common mistakes

• Not excavating deep enough — An inadequate sub-base means the paving sinks and rocks within a year, and it cannot be corrected without lifting everything.
• Laying paving above the damp course — It bridges the damp course and causes damp inside the house. The finished level must be at least 150mm below it.
• Bedding slabs on five blobs of mortar — The voids beneath collect water, which freezes and cracks the slabs. A full bed supports the slab evenly.

Questions people ask