Defect type
Critical · 3–5/5
Shower Waterproof Membrane Below Required Height
I checked the waterproof membrane height in the shower enclosure and it terminates below the reference heights I work from in AS 3740, leaving upper tile backing and adjacent framing unprotected. In my experience routine shower use then saturates the substrate, leading to rotten studs, blown plasterboard, and microbial growth behind the tiling. I see this frequently on owner-built or budget renovations where the tiler has waterproofed only to hob height.
Causes
- Membrane applied only to a nominal splashback height rather than the full wall zone referenced in AS 3740
- Tiler working from an outdated reading of AS 3740 for walls inside and outside the shower area
- Membrane over-trimmed during tile laying, reducing the effective height above the finished floor
Symptoms to look for
- Dark staining or paint blistering on the non-wet face of the shower wall
- Hollow-sounding or drummy tiles in the upper shower zone
- Spongy or moisture-affected skirting or flooring in the adjoining room
Remedies
- Strip tiles to the reference height and re-waterproof (reference AS 3740) before re-tiling
- Replace any moisture-damaged plasterboard, fibre cement or framing before re-lining
- Engage a licensed waterproofer and retain the compliance certificate for the next sale
Critical
Get an inspector through this property.
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