Yes, a qualified waterproofer can absolutely repair the physical damage caused by water ingress from a neighbouring property — but fixing the damage is often just one part of a bigger picture. You'll also need to think about stopping the source of the leak, understanding your legal position, and working out who is responsible for the cost of repairs.
What a Waterproofer Can Actually Fix
A waterproofer's job is to assess where water is getting in and apply the right systems to stop it. When the source is a neighbouring property, the types of repairs they can carry out on your side of the boundary include:
- Repairing or replacing waterproof membranes on walls, floors, and wet areas that have been saturated or compromised
- Sealing cracks and joints in concrete, masonry, or block walls where water has tracked through
- Applying tanking systems to below-ground or below-grade walls (common in basements or retaining walls)
- Treating efflorescence and salt damage caused by prolonged moisture exposure
- Restoring waterproofing in wet areas such as bathrooms or laundries that have been affected by rising damp or lateral water movement
- Installing drainage solutions such as French drains or channel drains along boundary lines to redirect water away from your structure
A good waterproofer will also help you identify whether the damage has affected your building's structure, and refer you to a builder or engineer if needed.
Stopping the Source First
Before any waterproofing repair will hold long-term, the source of the water needs to be addressed. If your neighbour's property is the origin — for example, a broken retaining wall, failed membrane on their deck, blocked downpipes, or poor site drainage — repairs on your side alone may only be a temporary fix.
You'll need to have a conversation with your neighbour, and ideally get a waterproofer or building inspector to assess both sides. BRANZ has useful guidance on moisture and water management in NZ buildings that can help you understand what's going wrong and why.
If your neighbour is uncooperative, you may need to seek advice through your local council, a solicitor, or the Disputes Tribunal.
Who Is Liable for the Damage?
This is where things can get complicated. In New Zealand, liability for water damage caused by a neighbouring property generally depends on:
- Negligence — did your neighbour fail to maintain their property in a reasonable way?
- Nuisance — is water consistently escaping their land and causing damage to yours?
- The nature of the boundary — shared walls (common in townhouses and apartments under a body corporate) have different rules to standalone properties
For body corporate situations, the body corporate rules and the Unit Titles Act 2010 set out responsibilities for shared structures and common areas. Your body corporate manager should be your first call.
For standalone properties, you may need legal advice. Consumer NZ has general guidance on neighbour disputes that's worth reading before you escalate things.
Your home insurance policy may also cover water damage from a neighbouring property — check with your insurer before spending money on repairs, as they may manage the claim and seek recovery from your neighbour's insurer.
Does This Work Require a Building Consent?
Most waterproofing repairs are maintenance work and don't require a building consent. However, if the repair involves significant structural work — such as rebuilding a retaining wall, altering drainage systems, or major remediation — a consent may be required.
Schedule 1 of the Building Act 2004 lists exemptions for routine maintenance and repair, but it's always worth checking with your local council if you're unsure. MBIE Building Performance has clear guidance on when consents are and aren't needed.
Waterproofing in wet areas (bathrooms, showers) must also comply with the relevant NZ Standard for wet area membranes and the NZ Building Code clause E3 (Internal Moisture). A qualified waterproofer will be familiar with these requirements.
What to Expect From the Repair Process
A typical waterproofing assessment and repair for neighbour-related water damage might follow these steps:
| Step | What Happens |
|---|---|
| 1. Inspection | Waterproofer assesses the damage and identifies the water pathway |
| 2. Moisture testing | Checks extent of saturation in walls, floors, or substrate |
| 3. Drying out | Affected areas may need to dry before repairs begin |
| 4. Surface preparation | Damaged materials removed, surfaces cleaned and primed |
| 5. Waterproofing applied | Membrane, sealant, or tanking system installed |
| 6. Drainage improvements | Additional drainage added if needed to manage future water |
| 7. Reinstatement | Tiling, plastering, or painting completed by relevant trades |
Products used may include membranes and sealants from suppliers such as Sika, Ardex, or Mapei, depending on the application.
When to Call a Professional
You should engage a qualified waterproofer as soon as you notice signs of water ingress — don't wait for the damage to worsen. Look for someone with experience in remedial waterproofing (not just new-build wet area work), as neighbour-related water damage often involves more complex diagnosis.
If structural damage is involved, you may also need a Licensed Building Practitioner (LBP). You can verify LBP registration at Licensed Building Practitioners.
For drainage work that connects to public stormwater systems, check with your council, as this may involve consented work or a licensed drainlayer — see Plumbers Gasfitters & Drainlayers Board for licensing information.
You can find qualified local waterproofers and related tradespeople on tradedirectory.co.nz.
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Licensed Building Practitioner (LBP)
