Waterproofing Inspection Checklist: 10 Things to Check on Your Auckland Property
Use this checklist to inspect your deck, flat roof, or balcony waterproofing system. Developed by Licensed Building Practitioners with experience across hundreds of Auckland waterproofing projects.
Safety First
Only inspect areas you can safely access. Do not walk on wet surfaces, work near edges without protection, or access steep roofs without proper safety equipment. If in doubt, book a professional inspection.
1. Visible Membrane Damage
What to check: Walk the entire deck or roof surface and look for cracks, splits, blisters, bubbles, or punctures in the membrane. Pay close attention to high-traffic areas and around furniture legs or pot plants.
Why it matters: Even small cracks in a membrane can allow water to penetrate into the substrate, causing rot and structural damage that is far more expensive to repair than the membrane itself.
2. Seam & Lap Integrity
What to check: Check all membrane seams (where sheets overlap) and laps. Look for lifting edges, fish-mouths, or any separation between layers. Gently press along seams to check adhesion.
Why it matters: Seam failure is the most common cause of leaks in membrane waterproofing systems. A failed seam allows water to track beneath the membrane across a wide area.
3. Upstand & Wall Junction Detailing
What to check: Inspect where the membrane meets vertical surfaces (walls, parapets, door thresholds). The membrane should extend a minimum of 75mm up the vertical surface with secure, sealed termination.
Why it matters: Wall junctions are critical leak points. Water running down a wall can penetrate behind a poorly detailed upstand, causing concealed damage inside the wall cavity.
4. Penetration Sealing
What to check: Check around all penetrations: pipes, posts, balustrade fixings, skylights, and any other objects that pass through the membrane. The seal should be intact, flexible, and watertight.
Why it matters: Every penetration is a potential leak point. Sealant degrades over time, and movement in the structure can break the bond between the membrane and the penetration.
5. Drainage & Falls
What to check: After rain, check that water drains completely within 24-48 hours. No puddles (ponding) should remain on the surface. Ensure all outlets, scuppers, and downpipes are clear and flowing.
Why it matters: Ponding water accelerates membrane degradation, increases UV damage, adds weight to the structure, and provides a constant source of moisture for leaks to develop.
6. Outlet & Overflow Condition
What to check: Inspect all drainage outlets and overflow points. They should be clear of debris, securely connected, and the membrane should be properly dressed into the outlet fitting.
Why it matters: A blocked or poorly connected outlet can cause water to back up and find alternative paths, often into the building. Overflow outlets provide critical secondary drainage.
7. Surface Coating & UV Protection
What to check: If your membrane has a protective coating or paint finish, check for chalking, peeling, or wear. Some systems (especially liquid membranes) rely on coatings for UV protection.
Why it matters: UV radiation is the primary cause of membrane degradation in Auckland. A worn or missing coating exposes the membrane to accelerated ageing and early failure.
8. Substrate Condition (Underside)
What to check: If accessible, inspect the underside of the deck or ceiling below the roof. Look for water stains, damp patches, musty odours, swollen timber, peeling paint, or mould growth.
Why it matters: Signs of moisture underneath indicate a leak is already occurring — even if the membrane surface looks intact from above. Early detection prevents structural damage.
9. Movement & Structural Cracks
What to check: Look for signs of structural movement: cracking in the substrate, gaps between surfaces, doors/windows out of alignment. Check expansion joints are intact and flexible.
Why it matters: Building movement is normal, but it stresses the membrane. If the waterproofing cannot accommodate movement, cracks and leaks will develop at stress points.
10. Debris & Vegetation
What to check: Remove all leaves, dirt, moss, and plant growth from the membrane surface and drainage paths. Check for roots growing under the membrane at edges and in cracks.
Why it matters: Debris traps moisture against the membrane, blocks drainage, and creates an environment for biological growth. Roots can lift and damage membrane laps and edges.
When to Call a Professional
If your inspection reveals any of the issues above — or if you are unsure about the condition of your waterproofing system — contact a Licensed Building Practitioner for a professional assessment. Early intervention is always cheaper than waiting for a major failure.
At Your Subbie, we offer free on-site inspections across Auckland. We will assess your membrane system, identify any issues, and recommend the most cost-effective solution — whether that is a targeted repair or a full replacement.
Need a Professional Inspection?
Book a free, no-obligation waterproofing inspection with Auckland's Licensed Building Practitioners.