Retaining Walls and Level Changes in Villa Gardens: Drainage and Structure

Level changes in a villa garden or compound add shape and usable space, but the ground does not stay where it is put. A retaining wall is a structure that resists constant pressure from soil and water, and it has to be designed and built accordingly.

Why retaining walls fail

The most common cause is water. Soil behind the wall becomes saturated, gets heavier and pushes harder, with nowhere for the water to escape. Walls without drainage behind them bulge, crack and lean. The second cause is a foundation that is too shallow or poorly compacted.

Structure

Taller walls and walls supporting significant loads, such as a driveway or building above, need to be designed by a qualified engineer. Foundation size, reinforcement and wall thickness all depend on the height and the soil.

Drainage behind the wall

•     A free-draining layer of suitable granular fill directly behind the wall.

•     Weep holes or a drainage pipe to let water out at the base.

•     Ground above the wall shaped to carry surface water away, not behind it.

Waterproofing the retained face

Where the wall holds soil against a building or a basement, the retained face needs proper waterproofing. Damp ground against a wall that is not protected will cause staining and salts on the inside.

Finishes and planting

Capping and coatings protect the wall from weather. Planters and irrigation near the wall add water to the soil and should be designed with drainage in mind.

Signs of trouble

•     Leaning or bulging sections.

•     Horizontal or stepped cracks.

•     Water staining or salts on the wall face.

•     Settling of the ground above.

If you see any of these, have the wall assessed before the next rain, and keep people away from the base of a wall that is clearly moving.

Planning a level change or worried about an existing wall? Book a free site visit and we will assess structure and drainage together.