Garden slab installation

A professional installation ensures the surface remains level, drains correctly, and withstands the British climate without shifting or cracking. This guide covers everything from material choices to the latest 2025 pricing and regulatory requirements.

What Does the Work Involve?

• Site Preparation: Marking out the area and excavating the ground to a depth of approximately 150mm–200mm to allow for the sub-base and slabs.
• Sub-base Installation: Laying a minimum 100mm layer of MOT Type 1 crushed stone, which is compacted using a vibrating plate (wacker plate) to create a solid foundation.
• Setting the Fall: Ensuring a slight gradient (usually 1:60 or 1:80) away from the house to prevent water pooling or damp issues against the brickwork.
• Bedding: Laying slabs onto a full "wet" mortar bed (sharp sand and cement) rather than "spots" of mortar to ensure total support and prevent rocking.
• Priming: Applying a slurry primer to the back of non-porous slabs, such as porcelain, to ensure they bond correctly to the mortar bed.
• Jointing/Pointing: Filling the gaps between slabs with either traditional mortar or modern polymeric resin for a weed-resistant finish.

Typical Costs

The cost of slab installation varies significantly based on the material chosen and the complexity of the groundworks. Labour typically accounts for 50-60% of the total project cost.

Expect to pay more if your garden has limited access, as moving materials by hand or through a house increases labour time. Additional features like decorative edgings, integrated drainage channels, or complex patterns will also increase the final quote.

How Long Does It Take?

• Small Patios (up to 15m²): 2–3 days for excavation, base prep, and laying.
• Medium Patios (15m²–40m²): 4–6 days, depending on the number of cuts required.
• Large or Complex Projects (40m²+): 7–14 days, especially if including retaining walls or steps.
• Drying Time: You should avoid walking on fresh slabs for at least 24 hours, and wait 48–72 hours before placing heavy garden furniture.

DIY or Professional?

While laying a few utility slabs for a shed base is a manageable DIY task, a full patio requires significant physical labour and technical precision. Incorrectly calculated drainage can lead to water damage to your home’s foundations or damp issues in the walls.

Expert Tip: Professional installers have the heavy-duty machinery required to compact the sub-base properly; hand-tamping is rarely sufficient and often leads to sunken slabs within 12 months.

For porcelain installations, professional help is highly recommended due to the brittle nature of the tiles and the need for specialist diamond-blade wet saws for clean cuts.

Choosing the Right Tradesperson

• Check Qualifications: Look for members of the Association of Professional Landscapers (APL) or the British Association of Landscape Industries (BALI).
• Verify Experience: Ask to see a portfolio of recent work specifically using the material you have chosen (e.g., natural stone vs. porcelain).
• Waste Management: Ensure they hold a valid Waste Carrier License to dispose of your old turf and soil legally.
• Questions to Ask:
  • Will you be using a full mortar bed or "dot and dab"? (Avoid anyone who says dot and dab).
  • How deep will the MOT Type 1 sub-base be?
  • Do you include the cost of skip hire and permits in your quote?
  • What is your policy for working in wet weather?

UK Regulations

• SUDS (Sustainable Drainage Systems): If you are paving a front garden over 5m², you must use permeable materials or direct runoff to a lawn or border. Otherwise, you may need planning permission.
• Building Regulations: Paving must be at least 150mm (two brick courses) below the Damp Proof Course (DPC) of your house.
• Part M: If the patio is part of the main entrance to a modern home, it may need to comply with "Access to and use of buildings" regs regarding gradients and widths.

Common Problems

• Efflorescence: A white salty residue that can appear on concrete or natural stone; usually disappears naturally but can be treated with specialist cleaners.
• Reflective Cracking: Occurs when slabs are laid on a thin or unstable base, causing the joints to crack as the ground shifts.
• Spot Bedding Failure: Laying slabs on five spots of mortar creates voids where water collects, leading to "rocking" slabs and frost damage in winter.
• Poor Drainage: Water pooling in the centre of the patio or running back towards the house walls due to an incorrect fall.
• Staining: Natural stone is porous and can be stained by leaves, berries, or grease if not sealed correctly.

Frequently Asked Questions

Do I need to seal my garden slabs?

Natural stone like sandstone is porous and benefits from a breathable sealer to prevent staining and algae growth. Porcelain is non-porous and does not require sealing, though you can seal the grout joints.

Can I lay new slabs over an old concrete patio?

Yes, provided the existing concrete is structurally sound, crack-free, and sits low enough to allow for the new slabs without breaching the house DPC. You will need to use a primer to ensure the new mortar bonds to the old concrete.

What is the difference between "sharp sand" and "builders sand" for paving?

Sharp sand contains larger grit particles and is used for the mortar bed because it provides better drainage and strength. Builders sand is too soft and "fatty," which can lead to the bed collapsing or slabs shifting.

Why is my patio turning green?

This is usually algae or lichen growth, common in damp, shaded areas of UK gardens. Regular cleaning with a stiff brush and specialist patio cleaner, or improving sunlight access, will manage the issue.

Is porcelain better than natural stone?

Porcelain is more durable, slip-resistant, and low-maintenance, but it is more expensive to buy and install. Natural stone offers a unique, traditional look but requires more regular cleaning and occasional sealing.