How to Lay a Patio – DIY Guide
To lay a patio, excavate the area to 150–200mm depth, compact a hardcore sub-base, lay a sharp sand and cement mortar bed, then set your slabs level with consistent 10–15mm joints. Brush in pointing mortar once set. Allow 24–48 hours before walking on it.
Lay and Compact the Hardcore Sub-Base
Tip Type 1 crushed hardcore (MOT sub-base) into the excavated area and spread it evenly to around 100mm deep. Use a plate compactor to compact it thoroughly — work in overlapping passes until the surface is firm and does not shift underfoot. A poor sub-base is the number one cause of sunken or cracked slabs, so do not skip this step or rush it. Hire a plate compactor for the day if you don’t own one; a hand tamper is not adequate for anything beyond a very small area.
Mix and Lay the Mortar Bed
Mix a bed mortar of five parts sharp sand to one part cement — this is known as a semi-dry or ‘five-to-one’ mix and should hold its shape when squeezed but not be wet or sloppy. Lay it across the compacted sub-base to a depth of 40–50mm, then rake it roughly level before using a straight-edged board to screed it flat. Work in manageable sections — no more than one or two slabs at a time — so the mortar does not begin to set before you place each slab. If you’re also planning to lay individual paving slabs in a pattern, plan your layout on dry ground first.
Set the Slabs and Check for Level
Place each slab firmly onto the mortar bed and tap it down with a rubber mallet until it sits at the correct height and fall. Check each slab with a long spirit level and also check across multiple slabs to ensure a consistent surface. Use tile spacers or offcuts of timber as temporary joint guides to keep gaps uniform at 10–15mm. Do not stand on newly laid slabs — use a plank to spread your weight if you must reach across. Any slab that rocks needs to come up, have mortar added beneath the low point, and be reset.
Cut Slabs to Fit Edge Courses
Measure any cuts needed for borders or around obstacles, then mark the cut line clearly on the slab face. For straight cuts, score deeply with a bolster chisel and club hammer first, then snap cleanly. For more precise or curved cuts, use an angle grinder fitted with a diamond stone-cutting disc — always wear eye protection, hearing protection, a dust mask rated to FFP2 or higher, and gloves when cutting. Wet-cutting reduces dust significantly and extends disc life. The HSE guidance on construction dust is clear that silica dust from cutting stone and concrete is a serious long-term health hazard — control it from the outset.
Point the Joints and Allow to Cure
Wait at least 24 hours after laying before pointing, so the bedding mortar has time to firm up and slabs won’t shift as you work. For a traditional finish, mix a stiff three-to-one sharp sand and cement mortar and press it firmly into the joints using a pointing trowel, finishing just below the slab surface. Alternatively, use a proprietary kiln-dried jointing compound brushed dry into the joints and activated with a light water mist — follow the manufacturer’s method for the product you choose. Keep all foot traffic off the patio for at least 48 hours, and avoid heavy loads for 72 hours. Once complete, consider reading our guide on how to fix a garden fence panel to finish the space properly.
Frequently Asked Questions
Do I need planning permission to lay a patio in my garden?
In most cases, no. Laying a patio in a rear garden is generally permitted development in England. However, if the patio is in the front garden and covers more than 5 square metres with an impermeable surface, you will need planning permission or must use a permeable material. Check with your local planning authority if you’re unsure, or refer to gov.uk guidance on permitted development.
How thick should the mortar bed be under patio slabs?
A mortar bed of 40–50mm is standard for patio slabs. This gives enough depth to accommodate minor variations in the sub-base and slab thickness while providing a solid, stable foundation.
Can I lay a patio directly on soil without a sub-base?
No. Laying slabs directly on soil — even compacted soil — will result in movement and sinking as the ground shifts with moisture and frost. A compacted hardcore sub-base is essential for any durable patio. If you’re tackling a large outdoor project, our Garden Guide covers the full range of projects to help you plan the right sequence.
What is the best pointing mix for patio joints?
A three-to-one mix of sharp sand and cement, mixed stiff (not wet), is the traditional and reliable choice. Alternatively, proprietary brush-in jointing compounds are easier to apply and more resistant to weed growth — worth the extra cost for larger patios.
How long does a new patio need to cure before use?
Keep foot traffic off for at least 48 hours after the final slab is laid and pointed. Avoid placing heavy furniture or planters on the patio for 72 hours. Full mortar strength is reached at around 28 days, though normal use is fine well before that.
Rather than screeding the full mortar bed flat before placing each slab, experienced layers use a ‘spot bedding’ technique — placing five generous mortar dabs (one at each corner and one in the centre) and then screeding the slab level onto them. This makes it far easier to adjust height on individual slabs without disturbing adjacent ones, and gives a solid bond without air voids.
Sources
- HSE — Construction dust: silica and other dust risks — hse.gov.uk
- Planning Portal — Decking, patios and other hard surfaces (permitted development) — planningportal.co.uk
- Which? — How to lay a patio — which.co.uk
This guide is for general information only. Always work safely and follow manufacturer instructions. DIYnut accepts no liability for injury or damage arising from DIY work.
