Laying a Slab Patio
Paving slabs are available in a wide variety of shapes, sizes and colours. Some reconstituted stone (concrete) products are designed to look like real old stone paving slabs, whilst others may come complete with a 'bite' out of the corner to allow you create planting holes.
If you are building a patio next to the house, you must make sure that the top of the paving is at least 15 cm (6 in) below the damp-proof course (dpc), and that the surface slopes away from the house.
Prepare the Site
Establish a line that you can use as a straight edge; a house wall is a practical base line to work from. Mark out the area of the patio with pegs and string. Work out how the paving slabs will be laid; you may want to slightly adjust the size of the patio to reduce the number of slabs that you will need to cut. You will need to allow about 0.5-1 cm (1/4-1/2 in) for mortar joints, depending on whether your slabs are metric or imperial - check this with your supplier.
Install the Foundations
Clear the site and lay the sub-base using the method discussed earlier in this section.
Create a Slope
You will need to ensure that the patio will contain a slight slope to prevent rainwater from pooling on its surface. This can be done using a system of levelling pegs and is fully described in Creating a Drainage Slope.
Lay the Slabs
Once you have created a sloping sub-base, you can begin to lay the slabs. These will be laid directly onto the 5 cm (2 in) layer of sharp sand that made up the final layer of the foundations.
If the paved area adjoins the house, start at one corner along this line. Place the first row of slabs into position, using a 1 cm (1/2 in) wooden spacer between them to allow room for the mortar. When you are happy with the positioning, lay a strip of mortar (1 part cement to 5 parts of sharp sand) on the ground along each edge where the slab is to be laid, to form an area slightly smaller than the slab. If your slabs are larger than 45 cm (18 in), you will need to add a further line of mortar to divide the area into two halves. The mortar lines should be about 3-5cm (1 3/4 -2 in) high.
Place the slab into position and tamp it down using a wooden or rubber mallet; check it is straight with a spirit level. Continue with the rest of the slabs, using the wooden spacers in between each one. Remove the spacers before the mortar sets and while you can still reach them without walking on the paving.
Point the Slabs
After about two days, fill the joints with a semi dry mortar mix of 3 parts sharp sand to 1 part cement. This mix should have an almost crumbly consistency which will help prevent staining the surface of the paving. Scrape of any excess mortar before it dries, using a dowel to produce a neat, recessed finish.
Alternatively, use a dry bedding mortar (1 part cement to 10 parts sharp sand) to brush into the joints. Finish off by spraying with a watering can fitted with a fine rose.