A patio at the back of a town house can be an enormously valuable addition, creating a private outdoor room. You can do this simply with paving slabs, sand and, if there is not already a wall, some form of fencing.

First, take the measurements and then decide what size of slab to use – you don't want to have to cut a slab. Your measurement should be divisible by the size of the slabs.

You will need a little extra room to allow for laying the slabs and bedding them in. Put in pegs to mark the four corners. Tie string between the four pegs to mark the sides of the patio – try to remember that it is there and don't trip over it. A patio does not have to be a rectangle or a squaBuilding A Patiore but if you intend it to be, check that all the right angles are 90 degrees and that the diagonals are the same. Check the right angles by the 3, 4, 5 method. Measure 3 ft from the corner of the angle along one side. Mark it. Measure 4 ft along the other side. Mark it. Measure the diagonal between the two marks. If it is a right angle, the measurement will be 5 ft. Once you have the measurements exact, replace the string with boards.

The next stage depends on the surface you have inside your rectangle, or square or hexagon or whatever you have. If it is loose soil, you need to remove this if at all possible. If you are in the middle of a city and this is the only area you have, try to compress it by laying a plank across it and marching up and down. Get the surface as hard as you can. Rake the surface smooth. Lay two inches of hardcore, compress it, and lay two inches of sand on top of it. (It is possible to do without the hardcore if the surface is already subsoil.) Rake this smooth and check that it is level with a spirit level.

Work out on the sand exactly where the slabs will be placed. If you have extra space at either end, centre the slabs and leave a gap round the ends – this will later be filled with gravel or some other material. Move the boards in so that they mark the edges. You may have to adjust them slightly in order to have some 'give' as the slabs go down.

Start by laying the slabs at the house end. Start in the middle and lay the slabs from the centre outwards. Bed the first slab down firmly in the sand, making sure it is at right angles to the house wall before laying the second slab. When you have laid your first row, check that the row is level, using a spirit level on top of a plank laid across the slabs. Make any necessary adjustments before going on to the next row. When you have laid all the slabs, pour sand onto the surface of the patio and, with a stiff broom, sweep the sand into the cracks between the slabs. You will need to do this several times as the sand sinks down between the slabs. This filling of the cracks will stop the slabs moving. You may need to redo it a few times after rain, if the water washes the sand down, but eventually the sand will be firmly compressed both underneath and between the slabs and the pavement will be firm.

If you have a gap around the edge between the pavement and the wall (or the proposed site of a fence if there is no wall) fill this with gravel. This will hold the slabs in place.

If the area is not already walled, it is not difficult to erect a panel fence. These can be bought in sections from any DIY centre with a garden department. The easiest way of erecting the posts is to buy fence post spikes. These are hammered into the ground and the fence post fits neatly into the top of the spike. The bottom of the fence will have a tendency to rot if it is laid directly on the ground, so run a gravel board between the posts at ground level before screwing the panels in place.