Building a Masonry Retaining Wall? Avoid this!

Water & Moisture leeching through a masonry wall will lead to efflorescence, damp patches, delamination of the coating system to the wall, and unsightly staining.

A retaining wall is considered a Class 10 structure. Section P2.2.3 ‘Rising damp’ of the NCC states;

“Moisture from the ground must be prevented from causing—

(a)unhealthy or dangerous conditions, or loss of amenity for occupants; and

(b)undue dampness or deterioration of building elements.”

However, the NCC clearly states that this does not apply to a Class 10 structure where there is no necessity for compliance.

A diagram as to how to membrane the rear of the wall (known as the positive side) and mitigate ground water (ie agi drain) should be detailed in your engineering plans.

The predominate failure point is at the cold join where the first course of blockwork sits on the concrete footing. This has occurred in the attached photo above. To prevent this, I would recommend the following scope of works;

• neatly chisel off the excess mortar from the first course of blockwork/concrete footing

• apply caulk or fillet to the cold join and flash over join

• apply liquid or rubber membrane to wall and over fillet/flash join

• apply coreflute plastic or similar so it laps over the cold join

• install agi drain and connect ensuring slots correct direction

• install scoria or similar

• install a Non-Woven Geo Textile Membrane

• backfill

Good luck, and remember the devil is in the detail!