How To Lay A Patio
This guide provides a professional, streamlined approach to laying a patio, covering everything from the initial site survey to the final jointing for homeowners aiming for a durable, high-quality finish.
Key Takeaways
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Foundation is everything: A solid, compacted sub-base is critical to preventing sunken or wobbly slabs.
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Drainage matters: Always ensure a slight slope (1:80 gradient) away from your property to prevent water pooling.
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Use your tools: String lines and marker pegs are essential to keeping your rows straight and your heights correct.
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Materials: You will need MOT Type 1 for the sub-base, sharp sand for the mortar bed, and high-quality patio slabs for the surface.
What is a patio?
A patio is an outdoor paved area, typically adjoining a house, constructed using materials like concrete, natural stone, or porcelain laid onto a prepared sub-base and mortar bed.
Why a stable base matters
A patio is only as good as the ground beneath it. If you cut corners on the depth or compaction of your sub-base, your patio will shift, crack, or become uneven over time due to weather cycles and foot traffic. A proper installation ensures longevity and prevents costly repairs.
Materials and Tools Checklist
| Category | Items Needed |
| Base | MOT Type 1, Plate compactor |
| Bedding | Sharp sand, Cement, Mixer |
| Layout | Marker pegs, String line, Spirit level |
| Paving | Patio slabs, Rubber mallet |
| Finishing | Jointing compound, Trowel, Spacers |
How to Choose Your Paving
Your choice of material should balance aesthetics with maintenance:
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Natural Stone: Beautiful and unique, but often requires sealing to prevent staining.
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Porcelain: Extremely durable, stain-resistant, and low-maintenance; ideal for modern designs.
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Concrete: The most budget-friendly and versatile option, though it may weather over time.
Step-by-Step Installation Guide
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Plan and Set Levels: Use marker pegs to outline the perimeter. Connect these with a string line to establish your finished height. Ensure the line includes a slight slope (a 1:80 gradient, or 1.25cm drop per metre) away from the house to allow water to run off.
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Excavate: Dig out the area to a depth of 150mmâ200mm. Use your perimeter pegs as a visual depth guide.
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Install Sub-Base: Lay MOT Type 1 to a depth of 100mm. Compact it thoroughly using a hired plate compactor until it is rock-solid.
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Lay the Mortar Bed: Mix 1 part cement to 4 parts sharp sand. Lay this on the sub-base at a depth of 30mmâ50mm.
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Place Slabs: Set your first corner slab against your string line. Use a rubber mallet to tap it into the mortar bed until it is level.
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Maintain Gaps: Use spacers or consistent wooden offcuts to ensure uniform gaps between your patio slabs.
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Jointing: Once the mortar is set (usually 24â48 hours later), fill the gaps with a proprietary jointing compound or a semi-dry mortar mix for a clean, professional finish.
Common Mistakes to Avoid
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Ignoring the DPC: Never lay your patio above the damp-proof course (DPC) of your house; keep it at least 150mm below to avoid moisture transfer.
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No Drainage: A patio that is perfectly level will hold water; always use a string line to maintain the 1:80 gradient.
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Inadequate Compaction: Skipping the plate compactor will lead to a sinking, uneven patio within months.
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Ignoring Underground Utilities: Always check for gas, water, or electric lines before you start digging.
FAQs
How thick should the mortar bed be?
Your bedding layer should be between 30mm and 50mm thick to provide adequate support for the slabs.
Can I lay a patio directly onto soil?
No. Soil moves, freezes, and thaws. You must have a sub-base (MOT Type 1) to provide structural integrity.
When should I call a professional?
If your site has complex drainage issues, steep gradients, or you are uncomfortable working near existing building foundations, consult a professional landscaper.
