What if my garden requires a retaining wall after building my conservatory?

What are retaining walls?

Retaining walls are walls used at the boundary between different ground levels where the height of the ground on one side is different to that on the other.

Retaining wall design

To ensure they are effective, great care should be taken in the design of retaining walls. Their performance is dependent both on the condition of the ground being retained and on the ground supporting the wall. The size of the base will also vary according to these ground conditions, however as a rule of thumb it should be equal to between a third and two thirds of the wall’s height.

In addition, drainage behind the wall is essential in order to prevent the retained ground becoming waterlogged. This can be achieved by laying a perforated drain along the rear of the wall or by creating holes (weep holes) at intervals through the wall itself.

In short, the following factors must be considered:
• Identify the most appropriate retaining wall type for the situation (see right).
• Design the most economical wall for the conditions.
• Provide supporting calculations to prove the design and to satisfy your local authority Building Control department.
• Ensure the design is safe and stable.

Retaining wall types

Reinforced masonry wall

This style of wall employs reinforcement to offer greater levels of strength than a normal masonry wall. As such, they can resist greater retained heights - typically of between 1.2 and 3.0m.

Reinforced concrete wall

Reinforced concrete is significantly stronger and more robust than masonry. This type of wall is also more resistant to water penetration. They are usual constructed at heights of 1.8m or more.