What Ongoing Maintenance Should I Do After Professional Waterproofing?

Professional waterproofing is a significant investment in your home, but it won't look after itself forever. With a few straightforward maintenance habits, you can extend the life of your waterproofing membrane, prevent costly water damage, and keep your home compliant with the NZ Building Code. Here's what you need to know as a NZ homeowner.

Understand What Was Installed

Before you can maintain your waterproofing properly, it helps to know what system was applied. Common systems in New Zealand include:

• Liquid-applied membranes – used in wet areas like showers, bathrooms, and balconies
• Sheet membranes – often used under tiles or on decks
• Cementitious coatings – common in below-ground or tanking applications
• Polyurethane or acrylic coatings – popular on decks and flat roofs

Ask your waterproofer for a completion certificate, product data sheets, and any warranty documentation. Many products from suppliers like Ardex or Sika carry manufacturer warranties that depend on correct ongoing maintenance.

Regular Visual Inspections

Get into the habit of inspecting waterproofed areas at least twice a year — ideally in autumn before the wet season and again in spring. Look for:

• Cracks, bubbles, or blistering in the membrane surface
• Lifting or separating edges around flashings, upstands, and penetrations (pipes, drains)
• Discolouration, mould, or damp patches on adjacent walls or ceilings
• Grout or sealant that is cracking, shrinking, or going mouldy in wet areas
• Pooling water on decks or flat roofs that isn't draining away

Catch small issues early and they're usually a straightforward fix. Left alone, even a pinhole breach in a membrane can allow water to track under tiles or into framing, leading to expensive structural repairs.

Keep Drains and Gutters Clear

One of the most important — and most overlooked — maintenance tasks is keeping drainage clear. Blocked drains cause water to pond, which puts pressure on any membrane and dramatically shortens its life.

• Clear leaf litter and debris from deck drains and scuppers every few months
• Check that balcony and flat roof outlets are free-flowing before and after storms
• Make sure gutters and downpipes connected to waterproofed areas are clean and intact
• Avoid letting soil or garden mulch build up against waterproofed walls or foundations

Protect the Surface

Waterproofing membranes can be damaged by physical impact, UV exposure, and harsh chemicals. To protect them:

• Use furniture pads or rubber feet under outdoor furniture on waterproofed decks
• Avoid dragging heavy objects across membrane surfaces
• Don't use abrasive cleaners or high-pressure water blasting directly on exposed membranes — a gentle wash with mild detergent and a soft brush is usually sufficient
• If the membrane is UV-exposed (such as on a deck or flat roof), check whether it needs a topcoat or re-coat — many polyurethane membranes require this every 5–10 years depending on sun exposure

Wet Area Maintenance (Bathrooms & Showers)

In tiled wet areas, the waterproofing membrane sits behind the tiles, so you're mainly maintaining the grout and silicone sealant that protect it.

• Re-grout or re-seal cracked or deteriorating grout lines promptly
• Replace silicone sealant in corners and junctions (wall-to-floor, wall-to-wall) every 5–7 years or sooner if it shows signs of mould or separation — silicone is the flexible joint that accommodates movement and protects the membrane below
• Use a mould-resistant bathroom cleaner regularly to prevent mould growth that can degrade sealants
• Ensure your bathroom has adequate ventilation to reduce moisture build-up — this is also a requirement under the Healthy Homes Standards for rental properties

Exterior and Below-Ground Waterproofing

For retaining walls, foundations, or below-ground tanking:

• Keep garden beds and soil levels below any waterproofed flashings or damp-proof courses
• Check that surface water drains away from the building rather than towards it
• Inspect any exposed flashings or membrane terminations annually for lifting or cracking
• Be careful when gardening near waterproofed foundations — spades and stakes can puncture membranes

Keep Records

Maintain a simple home maintenance file that includes:

• The waterproofing product used and the installer's details
• Warranty documents and any maintenance requirements specified by the manufacturer
• Photos taken at installation and at each annual inspection
• Notes on any repairs carried out

This documentation is valuable if you sell your home or need to make a warranty claim. BRANZ provides excellent guidance on building maintenance records for NZ homeowners.

When to Call a Professional

Some maintenance tasks are straightforward DIY, but others need a qualified waterproofer. Call a professional if you notice:

• Active leaks or damp patches appearing inside the home
• Membrane delamination — areas where the membrane has lifted away from the substrate
• Failed flashings around penetrations, edges, or junctions
• Any situation where tiles need to be lifted to access the membrane
• The membrane is approaching the end of its expected service life and needs assessment

Waterproofing repairs in wet areas that involve structural elements or penetrations may also require a building consent — always check with your local council first. You can find qualified, experienced waterproofing professionals in your area on tradedirectory.co.nz.

Sources & Further Reading

• MBIE Building Performance – NZ Building Code
• BRANZ – Home Maintenance Guidance
• Tenancy Services – Healthy Homes Standards
• Sika NZ – Waterproofing Products
• Ardex NZ – Waterproofing Systems
• WorkSafe NZ – Working Safely at Height on Roofs and Decks