One of the aims of garden planning is to associate the garden with the house so that one unit is created. The garden, viewed through a window, should be a natural extension of the house. The eye should sweep freely across an open lawn to the perimeters, to the prospect of hidden surprises behind curves, or be drawn to an apparently distant focal point.

The uniting link between house and garden is the terrace, usually leading from the living room into the garden. The shape and size of the terrace are usually determined by the garden area and by aspect. Where a new terrace is being built, it should ideally harmonise in shape with the garden.

A garden design based on curved lines should be repeated in a rounded terrace, and a formal rectilinear garden outline should be echoed by a square or rectangular terrace. Existing terraces can be made to conform to a curved garden design by hiding sharp corners with low-growing shrubs, or by adding to the front a curved strip of contrasting stone material as a standing area for planters.

Rounded terraces can be straightened out to some extent by means of additional stones of different material and colour, or by planting slender pyramidal trees at either end of the terrace.

A sunny or lightly shaded terrace will be used as a living and entertaining area in summer. It must, therefore, be large enough to accommodate garden furniture, such as tables and chairs, and to give easy access to both house and garden. Even where the rear of the house faces north or east, and a sunny sitting-out area is better sited somewhere else in the garden, a terrace against the house still provides a natural link between house and garden. It pushes the garden away from the immediate house walls, creating a feeling of space and opening vistas.

Older houses are often raised well above the garden area, and an existing terrace may be an elevated platform shut off from the garden by a low stone balustrade. Here, ornate planters are perfectly at home, and formal planters placed along the balustrade, or pots containing trailing plants, enhance the mellowed brickwork.

The outline of the steps leading from the terrace to the garden can be softened with planters or with plantings of low, graceful shrubs on either side. The bed at the foot of a balustrade can be treated as for a retaining wall and planted with shrubs, perennials, annuals and bulbs.

Most modern houses are built with the ground floor raised only a few inches above ground level. The terrace is on the same level as the garden, and steps are therefore unnecessary. On any type of terrace, leave small planting pockets between the stonework for cushion-forming plants, such as artemisia, armeria, dianthus, thyme and small-leaved mint or even the tiny rock rose (helianthe-mum). Reserve these planting pockets for those parts of the terrace that are not used for furniture or frequent walking.

Small beds can be made at the rear of the terrace next to the house wall. Climbers - for example, roses intermingled with clematis - can then be trained up the wall and above the windows. This is not feasible on walls with large picture windows; these are better embellished with a slender pillar rose or a camellia on either side.

Dark corners near doors or on the shady side of the terrace are ideal for shade-loving perennials such as hosta, primula and lily-of-the-valley, and for shrubs like mahonia and skimmia.

In very small gardens, the paved terrace may cover the entire area. If a high wall surrounds the garden it can be decoratively covered with climbers growing in planters. Shrubs and other flowering plants can be grown in more planters, window-boxes, troughs and hanging baskets.

'Where space allows, a small, low pool, set off-centre, makes an attractive feature, planted with one or two water lilies.