Leaking Balconies
Water coming through from the balcony above is almost always the membrane — and almost never fixed by more silicone.
Leaking balconies are usually caused by a failed waterproof membrane beneath the tiles, blocked drainage, or cracked tile bedding allowing water into the slab. Fixing a balcony leak properly means lifting the tiles, removing the failed membrane, treating any concrete damage, installing a new compliant membrane system, and re-bedding tiles with correct falls to drainage. Sealants around tile joints are not a real fix. Romans Building Services assesses leaking balconies across Sydney before recommending repair, so the visible damage and the cause are both dealt with.
Last updated: 2026-05-29
What is leaking balconies?
A leaking balcony is one of the most common and most expensive problems in Sydney apartments. Water comes through the ceiling of the unit below, or shows up as damp patches on internal walls, or rots out window frames over time. The source is almost always a failed waterproof membrane under the balcony tiles, though drainage failures, cracked slabs and wall-junction failures all contribute.
Balcony waterproofing has a design life of 10–15 years when done properly. Older apartments are well past that, and many balconies have never had a proper membrane replacement since original construction. Even newer buildings often have balcony defects from rushed original waterproofing that fails within 5 years.
The fix is rarely simple. A proper balcony waterproofing repair means lifting tiles, removing bedding, inspecting the concrete slab, treating any damage, installing a new compliant membrane, and re-bedding tiles to correct falls. Cheap fixes — silicone around the edges, sealer painted on top — delay the real job and usually make it worse.
Signs to look for
- Water stains or damp patches on the ceiling below the balcony
- Cracked or loose tiles on the balcony surface
- Efflorescence (white salt deposits) on the underside of the balcony
- Rusty steel reinforcement visible in the balcony soffit (concrete cancer starting)
- Water pooling on the balcony instead of draining away
- Damp patches on internal walls adjacent to balcony door frames
- Timber door and window frames warping or rotting near the balcony
Why it happens
- Failed or perished waterproof membrane under the tiles (most common cause)
- Blocked or badly positioned balcony drainage outlets
- Cracked tile bedding letting water into the slab
- Inadequate or non-existent falls to drainage
- Wall-to-balcony junction leaks (where the balcony meets the building)
- Cracked slab from movement or concrete cancer below the membrane
- Original construction defects — membrane installed over wet concrete or dusty substrate
How urgent is this?
A balcony leak is damaging the apartment below right now — typically to ceilings, walls, and sometimes electrical systems. It will also be damaging the structural concrete in the balcony slab, which is a much more expensive fix if left. Get it inspected soon so you understand the scope, even if the full repair is staged over months.
How we fix it properly
Inspect and diagnose
Identify where the water is actually entering — membrane failure, drainage, wall junction, slab cracking. Often a combination. We probe the tile bedding, check falls, inspect drainage outlets and examine the underside of the slab for damage.
Lift tiles and remove failed membrane
Tiles come up along with bedding and the old membrane. For heritage or expensive tiles we carefully salvage what we can. Everything down to the concrete substrate is exposed and assessed.
Treat the slab
Any concrete cancer, cracks, or damage in the slab gets repaired before new waterproofing goes on. This is the step where quick jobs fail — if the slab is wet or damaged, the new membrane fails too.
Install a compliant membrane system
New waterproof membrane applied to manufacturer spec with proper upturns at walls, around penetrations, and into drainage outlets. Multiple coats with inspection between. Warranty-backed system.
Re-bed tiles with correct falls
Tiles re-laid on new bedding with correct falls to drainage (minimum 1:100). Grout and perimeter sealant to match. Done right, the balcony sheds water properly for the next 15+ years.
Typical cost range
Typical apartment balcony repair: $8,000 – $25,000. Multiple balconies staged across a strata building $50,000 – $300,000+. Depends on tile area, slab damage, and whether scaffolding is needed.
Every job is different. We give a firm quote after inspection.
Common questions
Can I just reseal the tile grout to stop the leak?
No. The water is not coming through the grout — it is coming through the failed membrane underneath. Regrouting or siliconing around the edges is cosmetic at best and often traps moisture, making the damage worse. The membrane has to be replaced.
How long does a proper balcony waterproofing job take?
For a single apartment balcony: typically 1–2 weeks including curing time between membrane coats. Strata-wide programs run 2–6 months depending on number of balconies and whether they are done sequentially or in parallel.
Is the balcony leak coming from my unit or the one above?
Almost always the balcony directly above. Water tracks down through the slab and appears below where it entered. Occasionally water can travel sideways within the slab, but in nearly every case the leaking balcony is directly overhead.
Who pays for balcony leak repairs in a strata building?
Depends on your by-laws. Typically the slab and the waterproof membrane are common property (strata pays) and the tiles are lot property (owner pays). Get advice from your strata manager — bylaws vary and insurance may cover some situations.
Leaking Balconies in your area
The causes and right fix for leaking balconies vary with local housing stock and exposure. Read the version closest to where you are:
Where we see leaking balconies most often
Some suburbs have more of this problem than others — the local housing stock, age, and coastal exposure all play a part. Click through for the local context.
Think you might have leaking balconies?
Send a photo or call Minas directly. We will tell you straight whether it needs doing now, or whether it can wait.