Tips for Laying A Patio
Laying your owncan be hard work. By doing so, you save a good deal of money, if not time; and for many people there is great satisfaction in doing it yourself.
Whatever form of surface you decide on, make sure that it is laid on a well-drained stable base; this will avoid problems of sinkage and water-logging. All topsoil must be removed because it contains organic matter, which will decompose and may settle. The surfacing material can sometimes be laid directly onto well-compacted subsoil, but usually a well-consolidated layer of hardcore (such as fragments of brick) is needed, covered with sand, ash, or hoggin (screened gravel).
Begin by drawing a scale plan on which are marked the lines of all the drains and the positions of manholes and water pipes. Now using manufacturer’s plans and leaflets work out an appropriate layout using standard paving sizes; try to avoid having to cut slabs.
LAYING PAVING SLABS
The easiest way of laying paving slabs is to put them directly on to the soil; but this requires a lightand a comparatively level site. It is not easy to get a good level on heavy , and uneven levels can cause shifting or even cracking of the slabs. On these soils, it is best to lay the slabs on a bed of sand; this saves the effort and expense of using a mortar base.
You need a firm and level base on which to work, so first prepare the ground. Dig down deep enough to bring the finished patio to the level you want. Allow for a slight slope across the paved area to drain rainwater away from the house. If the ground is firm, you need dig out only the softer areas and replace the soil there with well-compacted hardcore. On soft clay soils, however, it’s best to roll or firmly compact a 100mm (4in) thick layer of hardcore over the whole area, finishing it with a 50mm (2in) layer of sharp sand to fill in larger gaps.
Mark out the edges of the patio with pegs and string to ensure that the edges of the slabs make straight lines (individual slabs vary slightly in size) and use a builder’s square to make sure that your corners form right angles. Try to plan the paving in such a way that you will not have to cut any of the slabs; cutting is tricky work. Begin bedding slabs at one corner. You can lay a mortar bed under the whole of the slab; or you can lay five pads of mortar about 50mm (2in) high, one under each corner and one in the middle of the slab. Mortar used should be a 1:4 mix of cement and sand. Tap down each slab with a wooden mallet or with a hammer on a piece of softwood: treat the slabs gently to avoid breaking them. Level each slab against its neighbour and against your wooden peg reference points (which you take out progressively as work proceeds).
Leave 12mm (1/2in) wide joints between slabs and insert wooden spacers of that width to stop the slabs closing up. Joints can be filled in various ways. You can, for instance, mix a cement/sand solution and pour it into the joints. Or you can mix the cement and sand dry (the sand needs to be very dry) and brush the dry mix into the gaps; then you sprinkle the joints with a watering can fitted with a fine rose. Generally, the easiest way is to mix up a very stiff mortar and press it firmly into the joints with the edge of a pointing trowel. Don’t walk on the slabs for at least three days. If the patio is bounded by a wall at the bottom of the slope, leave a small gap between the slabs and the wall, filling the gap with pebbles to help.
If your patio is going to have really heavy use, it’s best to lay the slabs in a wet concrete mixture (1 part of cement to 6 of sand) at least 100mm (4in) deep. Use ready-mixed concrete to avoid hard work but make sure the site is ready when it is delivered. Guard against concrete burns by protecting your hands with gloves. The paving slabs are laid on the wet surface of the concrete after it has been tamped down and levelled.
Contrary to popular belief, concrete can be laid directly on to subsoil, so long as it is firm and stable. The only preparation you need to do is to make sure the ground has the necessary slope for drainage, and then to roll it thoroughly. Any soft spots should be dug out and replaced with rammed hardcore. If the subsoil is not so suitable, prepare the ground as if you were laying paving stones, with hardcore and sand.
You will now need to set shuttering, or form work, at the sides to keep the concrete in place when it is poured and keep it straight at the edges. Special steel shuttering and holding pins can be hired, but a cheaper alternative is to use old planks of timber, at least 25mm (1in) thick, set on their edges and held in place with pegs. Set a straight edge and spirit-level between the formwork on either side and hammer the shuttering down with a mallet until you get a level reading on the spirit level; then make fine adjustments in order to achieve a drainage slope.
Concrete is basically a mixture of cement (usually ordinary Portland cement), sharp (concreting) sand, coarse aggregate (stones), and water. For good quality concrete the proportions of these materials should be carefully measured and mixed. Always store the materials separately, and use heavy-duty plastic buckets to measure the ingredients (measuring by shovelfuls is not accurate enough). Avoid laying concrete in frosty weather. The standard mixture for this type of application is 1 part of cement, 2-1/2 parts of sharp sand, and 4 parts of 20mm (3/4in) coarse aggregate.
Again, you need a firm base for laying, and it is generally best to lay the broken pieces of slab on to a continuous mortar bed rather than on to mortar pads; the pieces are often triangular in shape and the mortar pad method would not give enough stability for these.
The first thing to do is to sort out the larger pieces with straight edges and to lay a number of these to give you a straight line along the edges of theor patio. Then you can infill with the smaller, irregular pieces in the middle. However, a more informal approach can also be attractive. This can be achieved by laying the paving with a deliberately ragged edge, over which trailing plants can grow. Whichever method you adopt, first lay the broken pieces loose, fitting them together in attractive combinations of shape and colour, before you begin to fix them in their mortar bed. Try to make your paving ‘jig-saw’ fit as neatly as possible, so that the joints are not unattractively wide.
Set some sort of edging around the area – timber for instance – then lay your bricks into a 37-50mm (1-½ – 2in) layer of mortar, leaving a 10mm (3/8in) gap between them, then grout them carefully with a dryish mix. Blocks and pavers should be set in the same way; though if arranged in interlocking patterns, they can be laid on a carefully levelled bed of sand, then bedded down with a plate vibrator.
These should be packed as close together as possible on a bed of mortar or concrete. Another method is to set them in a dry bed of mortar or concrete mix, then water them thoroughly with a sprinkler to set them. You can lay the cobbles at random or you can create patterns, by exploiting colour differences or by laying them in concentric circles or squares.