Garage Wall Efflorescence & Rising Damp Repair — Auckland Case Study
Case Study by Auckland Waterproofing Experts
Client Brief
A homeowner in Auckland was converting an underground garage into a usable rumpus room but had ongoing rising damp and efflorescence coming through the lower half of a concrete block boundary wall. Carpet had absorbed moisture at the wall-floor junction, and the paint finish was blistering with white, chalky salt deposits — a classic sign of moisture migrating through block work from higher exterior ground level.
SITE ASSESSMENT
What We Found
- Visible efflorescence across the lower 900mm of the block wall, concentrated near the base
- A painted concrete block wall coated only with standard interior paint, unsuited to hydrostatic or vapour-driven moisture
- Carpet and underlay staining and mould growth at the wall-floor junction
- No active plumbing leak — consistent with subsoil moisture and hydrostatic pressure typical of below-ground block walls on Auckland’s clay-heavy sections
Scope of Works
1. Strip-Out
Carpet, underlay, and skirting removed along the full length of the affected wall; remaining floor protected with plastic sheeting.
2. Substrate Preparation
Failed paint and surface laitance mechanically ground back with HEPA-filtered vacuum extraction, exposing a clean, sound block substrate free of friable, salt-contaminated material.
3. Substrate Cleaning
Wet-vacuumed and cleaned to remove dust and loose salts before coating, maximising membrane adhesion.
4. Waterproofing Membrane Application
A waterproofing membrane was built up in coats directly onto the bare block, fully sealing the porous substrate and bridging the wall-floor junction to stop moisture transfer from the exterior soil side.
5. Finish Coat
A top coat was applied over the membrane for a clean, paint-ready finish.
6. Before and After
Result
- Moisture ingress stopped at the source rather than masked with paint
- The wall-floor junction — the most common failure point in below-ground rooms — specifically detailed and sealed
- Client regained a fully usable, dry garage conversion with no further treatment needed for the life of the membrane system
Why Efflorescence Matters
Efflorescence is a symptom, not the problem — it signals moisture-soluble salts being carried to the surface as water evaporates through concrete or block. Painting over efflorescence without stopping the underlying moisture path is a common but ineffective fix, since the new paint will blister again. Correct treatment always starts with stopping the moisture source, then applying a purpose-built waterproofing membrane suited to below-ground applications.
