An owners corporation cannot fix a balcony leak by quoting the repair. Until somebody establishes where the water actually enters, every quote is a guess, and the cheapest guess usually wins. That is why the same balcony gets sealed three times in five years.
What the investigation actually involves
- Non-destructive first. Moisture mapping, thermal imaging and a targeted water spray test to reproduce the leak under controlled conditions. A spray test with thermal imaging typically runs around $3,000 on a larger or contested job, less on a single balcony.
- Then, only if needed, invasive. Lifting a tile or two, opening the membrane upturn at the door threshold, checking the drainage outlet. We open the least we can get away with, and only where the non-destructive work points.
- The findings, in writing. A report that names the entry point, explains the mechanism, and is specific enough to price. Not “waterproofing has failed”.
- A repair scope that can be tendered. Most balcony leaks trace to the door threshold, the membrane termination height, or the drainage outlet detail — and each of those has a different fix at a very different cost.
What it usually turns out to be
- Termination height. The membrane stops too low at the door or the upstand, and driven rain gets over it. AS 4654.2 sets the height by wind class, and the 150 mm default in most templates is wrong for a good number of Sydney sites.
- The threshold detail. Cavity sliding doors and flush thresholds are the single most common source we find. There is usually no waterstop where the door frame meets the membrane.
- Drainage. A blocked or badly set outlet ponds water above the membrane upturn. Sometimes the fix is a drain, not a membrane.
- Not the tiles. Tiles are not the waterproofing layer, and re-grouting almost never fixes a balcony leak. It just delays the diagnosis by a season.
Who pays, in a strata building
- In NSW, the balcony slab and the waterproofing membrane are almost always common property, which makes them the owners corporation’s responsibility to repair — even when the damage shows up inside a lot. Floor coverings and fitout inside the lot usually are not.
- Where the building is still within its statutory warranty period, a leaking balcony is very often a defect claim rather than a maintenance item, and the investigation report is the evidence that makes that claim work.
- We write the report so it does both jobs: it tells your contractor what to build, and it stands up if the matter goes to NCAT or to the builder’s insurer.
Indicative fees and turnaround
| Scope | Indicative fee (ex GST) | Turnaround |
|---|---|---|
| Leak investigation and report | $1,500 – $3,500 | On site within a week; report within two |
| Water spray test with thermal imaging | $3,000 | Half to full day on site |
| Remedial waterproofing design and specification | $2,500 – $5,000 | 2 – 3 weeks |
| Regulated design and design compliance declaration | Included in the design fee | Issued with the design |
| Independent verification during the works | $2,400 – $3,200 | Staged, across the build |
Bands are the middle of our own fee book — the median to upper-quartile of 217 itemised fees on real ECE projects. They are indicative and ex GST. Every project is quoted on its own brief.
Common questions
Do we need an engineer, or can a waterproofer just quote the repair?
A waterproofer can quote a repair, but they will quote the repair they install. On a single obvious defect that is fine. On a balcony that has already been sealed once and is still leaking, or on any building where the cost will be levied across owners, you need the diagnosis separated from the person selling the fix. That is the whole point of engaging an engineer: the scope is written by someone with nothing to sell you afterwards.
Is the waterproofing design on a remedial balcony a regulated design?
On a Class 2 building, yes. Waterproofing is a building element under the Design and Building Practitioners Act 2020, so the remedial waterproofing design is a regulated design and needs a design compliance declaration. We prepare and declare that work under the Structural Engineering class of DEP0001529. Note the declaration is issued by us and lodged on the NSW Planning Portal by the registered building practitioner — that lodgement duty sits with the builder, not the designer.
How long before we can put the repair out to tender?
Typically three to four weeks end to end: site attendance within a week of engagement, investigation report about a week after that, and the remedial design and specification two to three weeks later. If the matter is urgent — an active leak into a habitable room, or a warranty deadline — say so at the brief and we will sequence it.
Can you inspect every balcony, or just the one that is leaking?
Both, and on a building with a pattern of leaks the whole-building look is usually better value. If three balconies of the same construction are leaking, the fourth is not far behind, and pricing one remediation across all of them beats four separate mobilisations. We will tell you at the inspection which it is.
Will the report stand up at NCAT or against the builder's insurer?
It is written to. Our reports state observations separately from opinion, cite the Standard or NCC clause that the construction departs from, and carry photographic evidence tied to locations. Where a matter is heading to a formal dispute we can issue it as an expert report in the applicable form.
Send us the brief.
Tell us the address, the building class and what you have been asked for. We will come back with a scope and a fixed fee — not an hourly estimate. Sydney, Melbourne and the Gold Coast; NSW, VIC and QLD.