Leaking balconies are one of the most common building defects in Sydney apartments and homes. The tiles look fine, but water is getting through to the slab, the unit below or the wall behind. Most of the time the problem is the waterproofing underneath, or the details at the edges.
Why balconies leak
- Failed or missing membrane under the tiles.
- Poor falls, so water ponds instead of draining.
- Inadequate upturns at walls and door sills, letting water run into the building.
- Blocked or undersized drains and overflows.
- Cracked tile beds and grout letting water sit on the membrane.
- Penetrations for balustrade posts and services that were not sealed.
The standard that applies
External above-ground membranes, including balconies, are covered by Australian Standard AS 4654.2, which deals with waterproofing design and installation, including membrane selection, falls, upturns, terminations and drainage. The National Construction Code requires external waterproofing to be suitable for the conditions.
Details that matter
- Falls to drains so water does not pond.
- Upturns at walls and under door sills high enough to stop water entering the building.
- Bond breakers and correct treatment at junctions so the membrane can move.
- Puddle flanges at drains so water reaching the membrane can escape.
- Overflows in case drains block.
- Sealed balustrade fixings that do not puncture the membrane.
How leaking balconies are fixed
Surface sealers over tiles can help with minor grout issues, but they rarely fix a failed membrane. Most proper repairs involve removing the tiles and bed, repairing the slab and any spalling, correcting falls, installing a new membrane with the right details, then re-tiling. See our guide to leaking balcony repairs.
Warranty
Residential waterproofing work in NSW is covered by the statutory warranties under the Home Building Act 1989. Membrane manufacturers often provide product warranties when their system is installed correctly. Ask for both, and for photos of the membrane before it is covered.
Balcony waterproofing in Sydney
See our balcony repair and waterproofing service. For apartment buildings, balcony remedial work is generally regulated under the Design and Building Practitioners Act 2020, and METCON is DBP registered.
Frequently asked questions
What Australian Standard covers balcony waterproofing?
AS 4654.2 covers the design and installation of external above-ground waterproofing membranes, including balconies.
Can a leaking balcony be fixed without removing tiles?
Sometimes for minor grout or sealant issues, but a failed membrane usually needs the tiles removed and the balcony re-waterproofed.
How long should balcony waterproofing last?
A properly designed and installed membrane, with correct falls and details, should last many years. Poor details are the most common cause of early failure.
