A professional waterproofer in New Zealand should provide you with a written warranty covering both their workmanship and the materials used. For quality residential waterproofing work, you can generally expect a warranty of 5 to 10 years, though this varies depending on the system used, the area being waterproofed, and the contractor's own guarantee policy.
Why Waterproofing Warranties Matter
Waterproofing is one of the most critical elements of any building. Failures in wet areas — bathrooms, decks, balconies, basements, and roofs — can lead to costly structural damage, mould, and health issues. A solid warranty gives you confidence that the contractor stands behind their work and that the products used are fit for purpose under New Zealand conditions.
Under the New Zealand Building Act 2004, all building work must comply with the NZ Building Code, including clauses E2 (External Moisture) and E3 (Internal Moisture) — note that E3 covers internal moisture/condensation, while wet area waterproofing requirements are primarily addressed under E2 and related acceptable solutions. Work that doesn't meet these standards is defective regardless of any warranty offered, so a warranty is your additional layer of protection on top of your legal rights.
What a Good Waterproofing Warranty Should Cover
A reputable waterproofer should provide a warranty that clearly states:
- Workmanship guarantee — typically 5–10 years, covering defects in how the waterproofing membrane or system was applied
- Materials warranty — usually backed by the product manufacturer (e.g., Sika, Ardex, or Mapei), often 10–15 years for quality membrane systems
- What is and isn't covered — for example, damage caused by subsequent building work, movement beyond normal tolerances, or owner misuse is commonly excluded
- The process for making a claim — who to contact, timeframes for response, and how remedial work will be carried out
- Transferability — whether the warranty transfers to a new owner if you sell the property (this can add real value)
Always ask for the warranty in writing before work begins, and keep a copy with your property records.
Manufacturer vs Workmanship Warranties
It's important to understand the difference between these two types:
| Warranty Type | Who Provides It | Typical Duration | What It Covers |
|---|---|---|---|
| Workmanship | The waterproofing contractor | 5–10 years | Installation defects, poor application |
| Materials/Product | The manufacturer | 10–15 years | Product failure under normal use |
| System | Manufacturer + approved installer | 10–15 years | Both, when an approved applicator is used |
Some manufacturers — such as Sika and Ardex — offer system warranties when their products are installed by trained and approved applicators. These combined warranties can offer stronger protection because both the product and the installation are covered under one document. Always ask your waterproofer if they are an approved applicator for the products they use.
Your Legal Rights as a Homeowner
Even without a warranty, you have rights. Under the Consumer Guarantees Act 1993, services must be carried out with reasonable care and skill. If waterproofing fails due to poor workmanship within a reasonable timeframe, you can seek a remedy from the contractor.
For licensed building work — which includes certain waterproofing in wet areas — the contractor may be required to be a Licensed Building Practitioner (LBP). LBPs can be held accountable through the LBP scheme for defective restricted building work, giving you an additional avenue for complaints.
Check with MBIE Building Performance if you're unsure whether your project requires an LBP or a building consent — some waterproofing work on existing structures may be exempt under Schedule 1 of the Building Act, but always confirm with your local council before assuming this applies.
Red Flags to Watch For
- A contractor who offers no written warranty or only a verbal promise
- Warranties shorter than 5 years for wet area or deck waterproofing
- No mention of which products or systems are being used
- Contractors who aren't familiar with NZ Building Code requirements for moisture control
- No evidence of being a Licensed Building Practitioner where required
Tips for Protecting Your Warranty
- Don't tile or cover the waterproofing membrane until it has been inspected and signed off
- Keep records of all product data sheets and application certificates
- Avoid making alterations to waterproofed areas without consulting the original contractor
- Report any signs of moisture ingress promptly — delays can void warranty claims
- Check whether your home insurance covers waterproofing failure and what documentation they require
When to Call a Professional
Waterproofing in wet areas (bathrooms, showers, laundries) and on decks and balconies is technically demanding work. Poorly applied waterproofing is one of the leading causes of building defects in New Zealand, according to BRANZ. While some surface preparation may be DIY-friendly, the actual application of waterproofing membranes in areas that must comply with the NZ Building Code should be carried out by a qualified professional — ideally an LBP with the relevant licence class.
If your waterproofing has failed or you're planning a new bathroom, deck, or roof project, find a qualified local waterproofer on tradedirectory.co.nz who can provide a proper written warranty and work that meets NZ Building Code standards.
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