The smallest house and garden can be enhanced by adding a well-designed patio or terrace. A variety of materials are available to give a wide range of surfaces and effects. They include coloured or textured concrete slabs, exposed aggregate slabs, cobbles, bricks, crazy-paving, open-screen blocks and frost-resistant ceramic tiles.
Careful initial planning of the patio or terrace is essential if it is to become an attractive integrated feature, complementing both house and garden. In most cases, the patio or terrace adjoins the house, serving as an outdoor extension for relaxation or meals on fine days. In a large garden, however, it may be set some distance away from the house in a warm sheltered spot. Or, on a very small plot, the patio itself may comprise the only “garden”, with gaps in the paving or containers for flowers or shrubs.
Where the patio or terrace is to occupy a portion rather than the whole of the garden plot, take the following factors into account before deciding precisely where to site it:
1. Likely suitable size of the patio area.
2. Proportions of the patio in relation to the house elevation and the rest of the garden.
3. Existing soil levels.
4. Access from the house to the patio.
5. The position that attracts maximum sunlight.
6. Direction of the prevailing winds.
7. Interesting focal points in the garden.
8. Less attractive views in the garden; siting the patio in a sunny sheltered corner is negated if, say, a tall ugly building dominates the view from it.
The floor of the patio or terrace should slope about 3 in. (or 7.5 cm) overall away from the house to prevent rain water collecting on the surface. Where the patio adjoins the house and even if the slab or walling is part of an integrated house and patio scheme, the patio structure must be at least 6 in. (or 15 cm) below the house damp-course level.
On a flat site the easiest way to ensure that water does not run back to the house is to interpose a pathway between the patio and the house and slope the patio away. Where the land slopes towards the house, excavation is necessary to form a ridge from which the patio can slope away. If your area is subject to constant heavy rainfall, you will -need a land drain sloping away from the house.
Width. The minimum effective width for a patio is 10 ft (3 m). A narrower width inhibits the easy movement of people using the patio. Any steps should be wide enough to accommodate two people at a time and not be too steep or too shallow.
Setting out the site.
The most important first step in patio construction is to set out the levels. What appears to be a flat piece of land can often be deceptive, concealing unseen slopes. To find the levels you will need a spade, hammer, long steel measure, spirit level, straight edge, a dozen timber pegs 2 in. by 2 in. (5 by 5 cm), each sharpened at one end, and some small blocks of timber.
1. Knock four pegs in the ground to mark the four corners of the site.
2. Measure a further area about 3 ft 4 in. (or 1 m) outside the four pegs and remove the topsoil from this area, taking care to extract any tree roots.
3. Remove the outer four marker pegs.
4. Stake three pegs along one side of the site. Place one peg at the highest point, one in the middle and one at the lowest level. On the centre peg place a
4 cm block of wood and on the lowest peg a 7.5 cm block.
5. Use your straight edge and level to line up the heights.
6. Dig out any uneveness, driving the pegs further in until the levels are finally correct. Work across the site, checking the levels as you go.
7. Finally, check the site area with the straight edge and level. Any depressions can be filled at this stage and tamped down.
Marking out foundations.
Care is needed when setting out for foundations and walls. Incorrect initial calculations will become increasingly obvious as the paving slabs are laid. They will not fit and the design will go out of true. To mark out true foundations, you need a home-made try-square and profile boards. The try-square is a right-angled timber triangle having sides in the ratio of 3:4:5, which you can easily make. A useful size for this type of work would be sides of 3 ft, 4 ft and 5 ft (say 91 cm, 1.2 m and 1-5 m). Two lengths of planed timber, mounted at right angles to each other and fixed on three 2 in. by 2 in. (5 by 5 cm) timber pegs, make up the profile boards.
The datum point is the reference point and check for all the patio levels, vertical and horizontal. All building levels are taken from this point. To establish the datum point position a single stake about 2 ft (or 61 cm) outside the area of the foundations. As this reference point is vital for the entire building operation, fix the stake in concrete so that it cannot be accidentally uprooted. Next, drive pegs at right-angles on each side of the datum marker and nail the first profile boards to them. Check with the spirit level that each profile board is upright and that the two boards are level with each other. Set up profile boards in the same way at each of the other corners.
The four sets of profile boards must be level with one another, even if the site slopes. Check the level of the four profiles, using a straight edge and spirit level. Use a try-square to check that the right angles are square. Another way of checking squareness is to measure the diagonals with a steel rule. If the lines are equal in length, the site is square.
If you plan a brick-walled patio, the wall will need its own concrete foundations or footings. Measure these out and establish guide lines from the profile boards. The width of footings depends on the height of the wall. For a low wall they should be a little over 6 in. (or 15 cm) wider than the thickness of the wall and at least 4 in. (or 10 cm) deep.
Footing-mix. A 1:21:4 (coarse aggregate) mix, mixed fairly dry, should be used for the concrete footings. In hot weather cover the footings with wet sacks. The foundations should be firm enough after a week to enable the bricks to be laid.
The methods of laying various surfaces for driveways and paths, also apply in general to the surfacing of the patio floor. Concrete slabs are among the most popular form of patio surface. Coloured or textured slabs give scope for design permutations. A scale plan of the patio floor facilitates ordering the correct amount of materials. As concrete slabs are difficult to cut, if possible adjust the surfacing area of the patio to a full slab module.