Waterproofing Retaining Wall

A retaining wall is useful for both aesthetic and practical purposes. It can create a usable area, or terrace a site that is sloping. It will provide an interesting profile on a featureless and flat garden. Whatever its purpose, it needs to be well made to ensure it is safe, trouble-free and intact.

Walls constructed of bricks, blocks or concrete need to be waterproofed to ensure hydrostatic water pressure does not cause damage to the concrete or mortar. A retaining wall that has not been waterproofed will show wet spots, efflorescence and not last as long due to water and salt ingress which eventually destroys the masonry and results in a collapsing wall.

What exactly is a retaining wall?

This is a wall that literally retains the earth, in case of a change in elevation. There are many types, a raised garden, or a large wall of many meters of height that is built to redirect water, prevent landslides or control erosion.


Gravity retaining walls: These prevent the earth from slipping by relying on their own weight. They are heavy and thick and made from bricks, concrete, or stones. They are tilted slightly towards the soil in order to compensate on the pressure.

Pile retaining walls: These rely on sheeting or piles that are driven into the ground to counteract the slope weight that is below or above the ground surface, just like a lever.

Cantilevered retaining walls: These have concrete structures that are cut into the slope, so the weight presses down. This counteracts the downhill flow to the earth. This is an excellent base.


Rock bank: This is a large collection of boulders and rocks that uses a slope that is naturally in place. It is sewn together with the natural vegetation to make it erosion resistant and strong.

Sleeper wall: This is very popular because it is cost-effective and easy to install. The timber will rot eventually; therefore concrete is a better option.

Masonry wall: This is a layer of crushed rocks or concrete stacked on each other. It can be made much higher than the normal retaining walls but it requires a good drainage and large footing.

Gabion wall: These are steel cages that have been reinforced and filled with stones, pebbles, and rubble to make it strong. They are permeable and ideal for areas with soil or drainage problems.

Dry stone wall: This is a mortar-free wall made with stones and rocks that have been chosen carefully and requires a broad, stable and strong base.

Core filled Block Wall: This is made up of a concrete poured footing with reinforcement then a block work wall which is core filled with concrete. This is strong, cost effective and can be finished with cement render or paint for aesthetics.

Rules of a good retaining wall:

  • Check the regulation: Depending on where you live, ensure you acquire a council permit to build the wall.
  • Soil type: The composition of the slope must be considered and the angle, so as to construct a strong and stable wall.
  • Solid base: Construct a very solid base, to ensure the wall remains flat.
  • Drainage system: A good drainage is extremely vital to a retaining wall otherwise the water pressure will eventually damage the waterproofing and in turn destroy the wall.
  • Check plumbing and cables
  • Ensure you waterproof the wall
  • Quality bituminous waterproofing membrane to prevent water ingress and long term damage.


For the retaining wall to last long and fulfill its purpose, ensure that you follow all the rules, and you make it strong and stable.

Contract a professional, who will design it the way it's supposed to be designed and ensure that it follows all the rules and guidelines laid out for retaining walls.

Typical Retaining Wall
Fig.1 - Typical Retaining Wall, Positive & Negative Applications.