A Sunken Garden Design – You can make your garden more interesting by providing occasional changes in level. By raising a garden or lowering a paved area, you can create small enclosures that are ideal as sheltered, outdoor living spaces especially when a retaining wall can double as bench seating. On the other hand, you may want to create a sunken haven for shade-loving plants or an elevated patch of lawn to act as a sun trap.
Planning the levels
Start by taking note or the shape of the sunken garden, the position of the house and large trees, and especially the existing contours of the land. Then decide which areas could be lowered or effectively raised, and whether the shape should be circular, square or irregular.
The basis of any raised or sunken garden is a retaining wall. There are various types of retaining wall and these are described in the article ‘Retaining Walls In Your Garden’. A simple timber wall, where the logs are set vertically, is another option.
Vertical timber wall
Narrow timber logs set into the ground can be used to make a retaining wall for curved shapes as well as straight ones. As long as they are properly set into the soil, vertical logs, either circular or square, will withstand any amount of stress from the soil and the moisture it contains, especially if you combine them with wooden paving to keep the logs in place.
For a 300-350 mm high wall, you should allow 150 mm of log below ground level. You can make the paving in a similar manner from shorter logs. To be solid and stable, they should be at least 100 mm long and tightly packed. Lay the paving first, and then use the deeper wall logs to wedge the pavers in place. Build up the soil behind the retainers. To be large enough for several people to lounge in comfortably, a circular sunken courtyard should have a diameter of three meters.