Defect Map

The Defect Map is an interactive section drawing of a typical NSW strata building: tap the seven zones where buildings actually fail, from roof membranes and balcony waterproofing to concrete spalling in the basement, and watch how one storm finds five ways in. It is general guidance, not advice: the drawing is a typical illustration, not your building, and defects can exist without visible symptoms, so for anything structural or unsafe seek a professional inspection promptly. Statistics: Building Commission NSW Strata Defects Surveys (2021, 2023, 2025), Class 2 residential apartment buildings. Built by Projex Pro, licensed Sydney remedial builders, NSW contractor licence 378139C. Planning the repairs? Our free DBP Check shows in 60 seconds whether the work needs registered designs and practitioners under the NSW DBP scheme.

The seven failure zones, in plain English

The drawing above is a typical NSW Class 2 strata building in section, with the seven places the Building Commission NSW defect surveys find failures most often: the roof and parapets, the facade, balconies, windows and doors, the wet area stack, the structure, and the basement. It is almost always water, and it almost always starts somewhere you cannot see.

Tap a numbered zone to see what fails there, the early warning signs and how serious it gets, then press Follow the water and watch one storm find five ways into the same building. If you have already done the Building Health Check, your flagged risk areas light up on the drawing automatically.

Defect Map FAQs

Common questions about where NSW strata buildings fail, why those defects happen, and how to catch waterproofing and concrete problems before they spread.

Waterproofing zones dominate: roofs and parapets, balconies and planters, wet areas and the facade. Structural issues such as concrete spalling and basement moisture follow. The seven zones on the drawing are ranked from the Building Commission NSW defect surveys, and water is the common thread through six of them.

Concrete spalling, usually called concrete cancer, is what happens when moisture reaches the steel reinforcement inside concrete. The steel corrodes and expands, which cracks and pushes off the surrounding concrete. Rust stains on concrete are the tell. It does not stabilise on its own, and the economical repair window closes as it spreads.

Usually a detail has failed rather than the whole balcony, and the official audits put most balcony leaks down to design and installation rather than age: a planter box holding water against the wall, a door threshold, or tiling laid over a tired membrane. The giveaway is drips or staining below after rain. By the time a stain shows, the water has usually been travelling for a while.

Because real rain does not choose one weak point, it finds them all: a pooled parapet, a balcony planter, a window head, a shower leaking into the riser, and water tracking down the facade cavity. Each leak can surface a floor or two from where it began, so five stains in five apartments are often one weather event exposing five tired details.

Water stains and damp patches, mould or a musty smell that returns after cleaning, bubbling paint, white salty streaks on masonry, and puddles that sit on balconies or walkways after rain. Mould in particular is a symptom, not the disease: killing the mould without finding the water is redecorating, not repairing.

The zones are drawn from the defect categories the NSW strata defects surveys record most often in Class 2 apartment buildings. The numbering follows the section from roof to basement, it is not a frequency ranking. Note too that fire safety systems are the second most common serious defect in NSW and are a separate discipline with their own annual statement, so the seven zones are not a complete defect checklist. The drawing is a typical building, not yours, so treat it as general guidance and get a professional inspection for anything structural or unsafe.

This page is general guidance, not advice. Next steps: the free Building Health Check scores the symptoms you can see against the NSW data in three minutes, The DBP Check shows whether the repair needs registered practitioners under the NSW DBP scheme, the Capital Works Fund Check tests whether your fund could pay for the fix, and the Council Approval Check shows which approval pathway the works need.