The first sign is usually below the balcony: a stain on the ceiling, drummy render on the wall, or rust streaks from a beam. Because the tiles are what you can see, the first repair is almost always cosmetic: regrout, reseal the joints, replace a cracked tile. It looks finished. The leak comes back with the next storm, because tiles were never what kept the water out.
What is actually under a tiled balcony
From the top down, a balcony that complies with AS 4654 has tiles, a bed of adhesive or screed, and then the waterproofing membrane on a substrate laid to fall towards a drain. The membrane is the only layer that is waterproof. Tiles and grout are porous and always let some water through; the system is designed on the assumption that they will. That water is supposed to reach the membrane, run down the fall, and leave through the drain or a drainage flange.
Where it fails
- Falls. If the substrate is flat, or falls away from the drain, water pools on the membrane. Standing water finds every pinhole and eventually gets through, or sits against the door and wall upturns until it tops them.
- Upturns and terminations. The membrane must turn up walls and door thresholds to a set height and be properly finished. A membrane stopped short at a door sill is the single most common balcony defect we find.
- Penetrations. Balustrade posts, downpipes and hose taps that pass through the membrane need to be detailed, not just sealed on top.
- Drainage. An outlet with no flange, or set proud of the membrane, leaves the lowest point of the balcony unable to drain. Blocked outlets and no overflow do the rest.
- Movement joints. Balconies move with heat and load. A membrane bridged across a joint with no allowance for movement tears.
- Age. Membranes have a service life. A twenty-year-old sheet or liquid membrane that has been baked under tiles is doing well to still be intact.
What a proper assessment looks at
A balcony leak is located, not guessed. Controlled water testing floods sections of the balcony in turn while the underside is monitored, so the entry point can be isolated to a threshold, a penetration or an area of membrane. Thermal imaging and moisture mapping show how far water has spread inside the structure. Falls are measured. Only then does anyone know whether the fix is a threshold detail, a drain, or a full membrane replacement, which are very different costs.
If a balcony is on a newer home or apartment, the assessment also establishes whether the defect is a departure from AS 4654, which is what a warranty claim or a QBCC complaint turns on. HydroIQ carries out the investigation and reports the findings; rectification is done by a licensed contractor, and our sister company S&S Remedial takes on that work.
Common questions
General information for South East Queensland home owners, not advice about your building or a legal matter. Standards and time limits change; check the current edition or rule before relying on a figure here.