How to Lay a Patio
Laying a Small Patio
A small paved area surrounded by attractive shrubs and low planting makes a perfect suntrap for relaxing in the garden. Provided you are not too ambitious, it is also relatively easy to achieve, using cast-concrete paving slabs available from any large DIY store or garden centre. The slabs are made by hydraulic pressing or casting in moulds to create the desired surface finish. Pigments and selected aggregates added to the concrete mix create the illusion of natural stone or a range of muted colours.
Laying heavy paving slabs involves a good deal of physical labour, but in terms of technique it is no more complicated than tiling a wall. Accurate setting out and careful laying, especially during the early stages, will produce perfect results.
- Angle grinder
- Bolster chisel
- Club hammer
- Face mask
- Hose or watering can
- Garden roller
- Handbrush or broom
- Spriit level
Shapes and sizes
There is a fairly standard range of shapes and modular sizes of paving available. Although it is possible to carry most slabs single-handed, it is advisable to have help when moving large slabs or heavy natural stones into place.
Planning the Area
To eliminate the task of cutting paving slabs to fit, try to plan an area of paving to be laid with whole slabs only. If the patio is to be laid next to your house, take your measurements from a convenient wall, or allow for a 100 to 150mm (4 to 6in) margin of gravel between the paving and wall. A gravel margin not only saves time and money by using fewer slabs, but also provides an area for planting climbers and for adequate drainage to keep the wall dry. Even so, allow for a 16mm per metre (5/8in per yard) slope across the paving, so that most surface water will drain into the garden. Any paving must be 150mm (6in) below the damp-proof course to protect the building.
Allowing for the joints
As paving slabs are made to fairly precise dimensions, marking out an area simply involves accurate measurement, allowing for a 6 to 8mm (1/4in) gap between slabs. Some slabs are cast with sloping edges to provide a tapered joint, and these should be butted edge to edge. Use pegs and string to mark out the perimeter of the paved area, and check your measurements before you start work.
Preparing a Sound Base for the Paving
Paving slabs must be laid upon a firm, level base, but the depth and substance of that base depends on the type of soil and the proposed use of the paving.
For small areas and light loads
For a small patio, remove grass and topsoil to allow for the thickness of the slabs, plus a 25mm (1 in) layer of sharp sand and an extra 18mm (3/4in) so that the paving will be below the level of surrounding turf and thus will not damage your lawn mower. Compact the soil with a garden roller, spread the sand with a rake, and level it by scraping and tamping with a length of timber.
For clay or peat soils
To support heavier loads, or if the soil is composed of clay or peat, lay a sub-base of firmly compacted hardcore (broken bricks or crushed stone) to a depth of 75 to 100mm (3 to 4in) before spreading the sand to level the surface.
If you are planning to park vehicles on the paving, increase the depth of the hardcore to 150mm (6in).
Laying Paving Slabs
Once you have laid your base, set up the string lines again as a guide for laying the edging slabs on the sand. Work in both directions from a corner. When you are satisfied with their positions, lift the slabs one at a time and set them on a bed of mortar (1 part cement : 4 parts builder’s sand). Add just enough water to make a firm mortar.
- Lay a fist-size blob of mortar under each corner, and one more to support the centre of the slab. If you intend to drive vehicles across the slabs, lay a continuous bed of mortar about 50mm (2in) thick.
- Lay three slabs at a time with 6mm (1/4in) wooden spacers between. Level each slab by tapping with a heavy hammer, using a block of wood to protect the slab. Check the alignment with a straightedge.
- Gauge the slope across the paving by setting up datum pegs along the high side. Drive them into the ground until the top of each corresponds to the finished surface of the paving, then use the straightedge to check the fall on the slabs. Lay the remainder of the slabs, working out from the corner each time to keep the joints square. Remove the spacers before the mortar sets. Don’t walk on the paving for two to three days, until the mortar has set. If you have to cross the area, lay planks across the slabs to spread the load.
- To fill the gaps between the slabs, brush a dry mortar mix of 1 part cement : 3 parts builder’s sand into the open joints. Remove any surplus material from the surface of the paving, then sprinkle the area with a very fine spray of water to consolidate the mortar. Avoid dry mortaring if heavy rain is imminent; it may wash the mortar out.
Cutting Slabs to Fit Narrow Margins
Sometimes it is impossible to plan an area of paving without having to use cut slabs to fill a border or to fit around immovable obstructions.
When cutting paving slabs with a chisel or an angle grinder, always protect your eyes with plastic goggles. An angle grinder throws up a great deal of dust, so wear a simple gauze face mask, too, as a safeguard.
- Mark a line across the slab with a soft pencil or chalk. Using a bolster and hammer, chisel a groove about 3mm (An) deep along the line. Continue the groove down both edges and across the underside of the slab.
- Lay the slab on a bed of sand and place a block of wood at one end of the groove. Strike the block with a hammer while moving it along the groove until the slab splits. Clean up the edge with a bolster.
A perfect cut
For a perfect cut, hire an angle grinder fitted with a stone-cutting disc. Using the grinder, score a deep groove as before. Tap along the groove with a bolster until the slab splits.
Making a Real-Stone Pathway
The informal nature of paths or patios laid with irregular-shaped paving stones has always been popular. The random effect, which many people find more appealing than the geometric symmetry of neatly laid slabs, is also less taxing to achieve. A good eye for shape and proportion is more important than a practised technique.
Choosing your materials
Use brokenif you can find enough of them, but in terms of appearance nothing compares with natural rock, which splits into thin layers of its own accord as it is quarried. Random broken stone is also ideal for paving and can be obtained at a very reasonable price if you can collect it yourself.
Laying the Stones
You can set out string lines to define straight edges for stone paving, although they will never be as precisely defined as those formed with regular cast-.
Arrange an area of stones, selecting them for a close fit but avoiding too many straight, continuous joints. Trim those that don’t quite fit with a bolster and hammer. Reserve larger stones for the perimeter of the paved area, as small stones tend to break away.
- Use a mallet or block of wood and a hammer to bed each stone into the sand until they are all perfectly stable and reasonably level.
- Having bedded an area of about 1sq m (1sq yd), use a straightedge and spirit level to true up the stones. If necessary, add or remove sand beneath individual stones until the area is level.
- When the main area is complete, fill in the larger gaps with small stones, tapping them into place with a mallet.
- Fill the joints by spreading more sand across the paving and sweeping it into the joints from all directions.
Alternatively, mix up a stiff, almost dry, mortar and press it into the joints with a trowel, leaving no gaps.
Use an old paintbrush to smooth the mortared joints, and wipe the stones clean with a damp sponge.