Waterproofing Inspection

An independent check of the wet-area membrane against AS 3740 — heights, junctions and penetrations — before the tiler covers it.

Book after membrane, before tiling

Call 07 3180 8041 — same-week availability

Why Waterproofing Is Inspected Before Tiling

Wet-area waterproofing is a hidden system. Once the tiler lays tiles over the membrane, the waterproofing cannot be seen or tested directly — its condition is only revealed later, usually by a leak into an adjoining room or the floor below.

Domestic wet areas are waterproofed to AS 3740 Waterproofing of domestic wet areas, with NCC Volume Two clause 3.8.1 (wet areas) setting the acceptable-construction baseline and the QBCC Standards and Tolerances Guide (clause 7) covering wet-area workmanship. The standard sets membrane heights, junction detailing and penetration sealing — the exact things that fail when they are wrong.

Waterproofing failures in wet areas are consistently reported as one of the most common defects in Australian residential construction, and a leading source of home warranty claims in the years after completion. The inspection window closes the day the tiler starts.

What's Included

Shower wall membrane height (AS 3740, min 1800mm)
Membrane continuity at floor-to-wall junctions
Bath hob height and tie-in to wall membrane
Vanity and laundry tub interfaces
Penetration seals — taps, waste, floor grates
Membrane condition — pinholes, even application
Substrate preparation and priming
Compatible sealants at expansion joints
Same-day PDF report with photos

From $550

Includes GST

Critical Elements We Verify

Heights

Membrane termination vs AS 3740

Junctions

Floor-to-wall continuity

Penetrations

Taps, wastes and grates sealed

Substrate

Priming and preparation

What we check at waterproofing stage

The inspection works through each wet area against AS 3740, which sets the membrane heights, junction detailing and penetration sealing that keep water inside the area it is meant to stay in.

Shower membrane termination height — AS 3740 requires the walls of an enclosed shower to be waterproofed to at least 1800 mm above the finished floor. We measure it; the most common failure is a membrane that stops short.
Membrane continuity at the floor-to-wall junction — the membrane has to be continuous across the junction with no missed corners, per the membrane provisions of AS 3740 (clause 2.5). Corners and internal angles are where continuity is most often lost.
Bath hob height and tie-in — the hob is waterproofed and the membrane tied into the adjoining wall membrane so water cannot track behind it.
Vanity and laundry tub interfaces — junctions around built-in vanities and tubs, which are frequently missed because they are detailed late.
Penetration seals — the shower head, taps, waste outlets and floor grates checked so the membrane is sealed to each penetration per AS 3740 (clause 2.7).
Membrane thickness and finish — the applied membrane checked for pinholes, thin spots and uneven application that would let water through.
Substrate preparation — the substrate primed and prepared per AS 3740 (clause 2.4) before the membrane went on, since a membrane over an unprepared substrate does not bond reliably.
Sealants at movement joints — compatible, correctly-placed sealant at expansion and control joints so the membrane is not the only thing accommodating movement.
Documentation — whether the waterproofer's product warranty and certificate are available on request for the products used.

Common waterproofing defects and the standards they fail

The defects below are standards-based patterns rather than site-specific claims. Any inspector working to AS 3740 checks for the same items.

Membrane height undershoot — a shower wall membrane finished at, say, 1500 mm is a 300 mm shortfall against the 1800 mm AS 3740 requires. Water above the membrane line reaches the substrate directly.
Missed corner at a hob-to-wall junction — a gap in the membrane at an internal corner breaks the continuity AS 3740 clause 2.5.4 requires, and corners are exactly where water collects and tracks.
Penetration collar not sealed to the membrane — a waste or tap penetration that is not sealed into the membrane per AS 3740 clause 2.7.3 leaves an open path straight through the waterproofing.

Why the cost case is one-sided

A waterproofing defect found before tiling is corrected by touching up the membrane — a small, cheap job. The same defect found after tiling, once a leak appears, means removing and reinstating the tiling, the screed and the membrane in the affected area, plus repairing whatever the water damaged in the adjoining room or the storey below. The rectification cost of a failed shower routinely runs to several thousand dollars against an inspection that is a fraction of that — which is why the membrane is inspected while it can still be touched.

External and trafficable wet areas

Balconies, podiums and other external trafficable areas are waterproofed to AS 4654 Waterproofing membranes for external above-ground use rather than AS 3740, and they carry extra risk because they take direct weather and foot traffic. Where the plans call up an external membrane, we check the same fundamentals — termination heights, junctions, penetrations and falls to the drainage outlet — against AS 4654, along with the drainage and overflow detailing that keeps water off the door threshold.

Falls are the item most often wrong on external areas. A membrane laid without enough fall lets water pond, and standing water eventually finds any weakness in the membrane. The fall is set by the screed under the membrane, not the membrane itself, so we check the substrate falls to the outlet before the membrane goes on — a fall problem is far cheaper to correct at this stage than after tiling.

When to book: after the membrane, before the tiler

The waterproofing window is short. The membrane has to be applied and cured so it can be assessed, and the inspection has to happen before the tiler arrives. Once tiling starts, the membrane is covered and the opportunity is gone.

In practice that means booking as soon as the waterproofer signs off and before the tiling is scheduled — often only a day or two apart, so timing matters. We turn the report around the same day for most inspections with photographs and clause references, so any item can be corrected before the tiler is on site.

Where waterproofing sits in the sequence

Waterproofing follows the internal fit-out stages and precedes tiling and handover. Before it, the enclosed (lock-up) inspection confirms the building is weather-tight, and the frame inspection confirms the structure. After waterproofing and tiling, the practical completion inspection is the final check before handover.

Frequently asked questions

When should I book a waterproofing inspection?

Book the waterproofing inspection after the membrane is applied and cured, and before the tiler starts. That is the only window where the membrane itself is visible — once tiling goes on, the waterproofing is permanently covered and can only be assessed by its consequences, usually a leak.

How long does a waterproofing inspection take?

Wet areas are inspected room by room — showers, bathrooms, laundry, any balcony or powder room — so the time depends on how many there are. A typical new home takes about an hour. We photograph each junction, height and penetration and issue the report the same day for most inspections.

What happens if the waterproofing inspection finds a defect?

Each item is recorded with a photo, a location and the AS 3740 clause it fails. You forward it to your site supervisor before the tiler starts. A membrane defect corrected before tiling is a small job; the same defect found after tiling means lifting tiles, screed and membrane to reach it.

Do I attend the waterproofing inspection?

No. We coordinate access with the site supervisor and attend in hi-vis and safety boots. You receive the same-day PDF report with photographs and clause references, and a follow-up call to walk through anything flagged.

How does your waterproofing inspection differ from the waterproofer's certificate?

The waterproofer issues a certificate stating the membrane was installed to AS 3740. That certificate is the installer certifying their own work. Our inspection is an independent check of the same work against the same standard, written for you — heights measured, junctions and penetrations checked, before anyone tiles over it.

Which wet areas do you inspect?

Every wet area the plans call up — showers, bathrooms, ensuites, powder rooms, the laundry, and external areas like balconies or podiums where a membrane is specified. Each is assessed against AS 3740 and, for external trafficable areas, the relevant balcony and deck provisions.

How much does a waterproofing inspection cost?

A standard residential waterproofing inspection is $550 including GST across Brisbane and the Moreton Bay corridor. That covers the site attendance, the same-day photo-tagged report with AS 3740 references, and a follow-up call. Homes with a large number of wet areas or external membranes are quoted individually.

Free waterproofing checklist (PDF)

The membrane heights, floor-to-wall junctions, penetrations, hobs and external falls we check against AS 3740 and AS 4654.2 — the same list our inspectors run on site. Free, no email required.

Download

See all our free inspection checklists for every build stage.

Waterproofing is one of the last hidden systems before handover. See the enclosed inspection before it, the practical completion inspection that follows, or the full construction stage inspections sequence.