Inadequate Waterproofing Membrane at Door Threshold
Inadequate Waterproofing Membrane at Door Threshold is a cosmetic moisture defect SURE inspectors have documented across 2 inspection reports.
Causes
- Failure to comply with AS 3740:2021 Clauses 3.7 (Surface Preparation) and 3.13 (Penetrations)
- Application of membrane over contaminated or unclean surfaces
- Poor surface preparation prior to membrane application
- Failure to comply with AS 3740:2021 Clauses 4.8.1 and 3.13
- Improper installation of the waterproofing membrane
Symptoms to look for
- Potential for water penetration around the toilet waste pipe
- Compromised waterproofing system integrity
- Inadequate adhesion of the membrane
- Moisture tracking beneath the threshold into adjoining areas
- Compromised integrity of the waterproofing barrier
Remedies
- Clean, dry, and re-waterproof the affected area around the toilet waste pipe in accordance with AS 3740:2021 Clauses 3.7 and 3.13, ensuring proper substrate preparation and adhesion of the membrane to provide a durable and watertight seal.
- Rectify the waterproofing membrane at the door stop to form a continuous, fully bonded waterproof barrier in accordance with AS 3740:2021 Clauses 3.13 and 4.8.1, ensuring no breaks or voids occur at the junction between the floor membrane and the door stop/threshold.
- Reinstall tiles so that the finished level is flush with or below the top of the water stop
- Reinstate the waterproof membrane to be continuous with the water stop and substrate
- Remove tiles at water stop junctions
Include this check in your next inspection.
Typically a low-severity finding, but worth documenting before maintenance work. Every SURE inspection includes 12 months of free advice.
Curated entries in Moisture
- Curated 2–4/5Excessive Moisture Readings
A non-destructive moisture meter has detected elevated readings in wall or ceiling linings at the time of inspection. Elevated readings alone do not confirm the source - they indicate that water is present in a material and that further investigation is warranted to rule out active leaks, drainage failure, or concealed termite activity.
- Curated 1–4/5Deteriorated Splashback Sealant
Failed or missing sealant at the benchtop-to-splashback junction allows water to track behind the cladding and into the wall cavity, leading to substrate damage and potential mould growth. This junction is one of the most commonly missed maintenance items in kitchens across Perth's mid-century and newer housing stock.
- Curated 2–4/5Excess Moisture in Walls Adjacent to Wet Areas
Elevated moisture readings on wall linings next to bathrooms and showers indicate water is escaping the wet area - either through a failed waterproofing membrane or a leaking pipe inside the wall cavity. Left unaddressed, trapped moisture breaks down plasterboard, promotes mould, and can rot the framing behind the lining.
- Curated 1–3/5Tile Grout Deterioration in Shower
Grout failure in shower recesses is one of the most common moisture-pathway defects our inspectors record, present in 9.4% of all reports. Deteriorated or missing grout - including at screen junctions and wall-floor junctions - allows water to migrate behind tiles, saturating the substrate and ultimately causing waterproofing membrane failure, tile de-bonding, and concealed wall framing damage. AS 3740 requires shower wet areas to be fully waterproofed; grout condition is a primary indicator of whether that waterproofing system remains effective.
- Curated 3–5/5Bath Hob and Surround Missing Waterproof Membrane
I inspected the bath hob, step-down, and vertical wall returns and could not confirm a continuous waterproof membrane behind the tiling. Reference: AS 3740. In my experience overspray and splash then tracks into the sub-tile substrate over time. I see this most on renovations completed before the post-2004 tightening, and still on recent unlicensed work.
- Curated 2–4/5Shower Floor Fall Insufficient to Drain to Waste
I ran water in the shower recess and it ponded on the floor rather than draining cleanly to the waste - I measured a fall flatter than the 1:80 reference I work from (AS 3740). In my experience standing water then loads the grout lines, saturates the membrane at the low point, and tracks under the hob into the adjacent room. I often see this where the screed has been laid flat to suit a large-format tile layout.