Paving slabs (or flags) are widely used for paths and patios and a trip to any garden centre or builders' merchant will demonstrate the enormous range of sizes, shapes and colours available.

Size and Shape

The most commonly used size of patio slab is 450x450 mm (18x18 in), although larger and smaller slabs are available. You could choose to lay your paving using just one size of flag, or perhaps use a range of squares and rectangles to produce a random-looking pattern. There are also geometric shaped slabs: hexagons, trapezoids and radial units to form arcs and circles.

Texture

Flags are available in a number of different textures. Riven concrete flags are manufactured to look like traditional old stone flags. Whilst some can look incredibly authentic, the cheaper versions tend to look somewhat unrealistic. If you are considering a riven slab, bear in mind that its bumpy, uneven surface may mean that you find it impossible to keep your patio furniture from wobbling!

Other textures may be found, such as coarse finish, exposed aggregate, smooth ground or polished styles. There are also slabs that have a pattern etched into them, or that imitate brick, cobble or sett paving. However, you should remember that any rough or etched flags will attract mosses and lichens, so they will need to be cleaned regularly with either Jeyes fluid or by using a power hose.

Colour

Slabs are available in a huge range of natural grey, brown, red and yellow colours, although you will also find a number of more artificial looking colours. Bear in mind that flags will go darker when wet, so ask for them to be wetted down to see how much they change colour. A dark slab in a sunny situation will absorb light (and heat), whilst a pale one will reflect the light and can brighten up a shady courtyard or basement.

Quantities

If you are laying a pattern with slabs of different sizes or colours, draw a plan on graph paper to calculate the number of each required, allowing up to 5% extra for breakages. Try to work to dimensions that minimise the need to cut slabs.