What remedial building services cover in NSW, how the DBP/Class 2 rules work, what projects actually cost, and how a strata committee should choose a remedial builder — a complete 2026 guide for owners corporations.
Every strata committee in New South Wales eventually opens the same kind of letter: an engineer's report, a leaking balcony above a car space, a spalling slab shedding concrete onto a path, or a cladding notice that turns "we'll deal with it later" into a decision with a deadline. Remedial building is the work that follows — diagnosing and repairing defects in an existing building so it is safe, watertight and compliant again. This guide explains what remedial building services actually cover in NSW, how the work is regulated, what it costs, and how an owners corporation should choose a contractor.
It is written for strata committees, owners corporations and building managers weighing up a remedial program for the first time. For the full service scope and credentials you can see how the Atomic Projects remedial team approaches a whole-of-building program — but the aim here is to give you the map before you commit to anything.
Remedial building services are the specialist repair and restoration of defects in existing buildings — concrete cancer, water ingress, failed waterproofing, cracked facades, combustible cladding and structural movement. Unlike general building, remedial work is investigation-led: the contractor diagnoses the cause of a defect before repairing it, so the fix lasts rather than returning in a few years.
The category spans several overlapping disciplines, and most real strata projects touch more than one of them. The main areas are treating concrete cancer and spalling, waterproofing remediation to stop water getting into the structure, repairs when a balcony starts leaking, replacing non-compliant cladding, and strata building defect rectification where an engineer or inspector has already listed what needs fixing. A good remedial builder treats these as one connected problem, because in most buildings they are: water that gets in through a failed balcony membrane is often the same water that is corroding the reinforcement in the slab below it.
A renovation changes how a building looks or works; a repair patches a symptom. Remedial building targets the underlying defect and its cause. A painter covers a damp stain; a remedial builder finds the failed membrane behind it, removes the affected material, treats the cause, and reinstates to standard — so the stain does not come back next winter.
The practical difference is sequence. General building starts with a scope and a price. Remedial building starts with an investigation: opening up a sample area, testing, and identifying why the defect happened before anyone commits to a method. That is why a remedial quote given without opening anything up is a warning sign — the hidden damage does not disappear, it simply arrives later as a variation. It is also why a competent remedial contractor has a duty to warn the owners corporation when a proposed "cheap fix" will not hold, even if that is not what the committee wanted to hear.
Any owners corporation or building owner with a defect affecting safety, waterproofing or structure needs a remedial builder rather than a general handyman. The usual triggers are an engineer's or building inspector's report, a Section 106 defect claim, a cladding notice, recurring leaks that keep coming back after patching, or capital-works planning for an ageing strata building.
The scale of the problem is not marginal. Building Commission NSW research released in 2025 found that a majority of recently completed strata buildings had at least one serious defect — you can read the detail in our summary of the government's strata defect research. For most committees the question is not whether the building will need remedial work, but whether it is planned and budgeted or handled as an emergency after something fails.
For Class 2 buildings — apartment and mixed-use residential — yes. The NSW Design and Building Practitioners (DBP) Act requires registered practitioners and lodged, compliant documentation for building work on Class 2 buildings. Engaging a Class 2 DBP Registered Building Practitioner protects the owners corporation's warranty and insurance position. Atomic Projects is a Class 2 DBP Registered Building Practitioner.
The building's classification under the National Construction Code (NCC) decides which rules apply, and the DBP regime has progressively widened the work it captures. In practice this means remedial work on an apartment block has to be designed, documented and carried out by registered practitioners, with declared designs lodged where required. For a committee, the simple protection is to confirm registration and a current NSW builder's licence before signing anything — unregistered work on a Class 2 building can leave the owners corporation exposed if a claim or an insurance question arises later.
The four that dominate NSW strata are water ingress (failed waterproofing and leaking balconies), concrete cancer (reinforcement corrosion and spalling), facade and cladding defects including combustible cladding, and structural cracking or movement. Water ingress is the most common and the most destructive, because over time it drives concrete cancer, membrane failure and timber decay throughout the building.
Waterproofing is governed by standards such as AS 4654.2 for external above-ground membranes, and concrete repair by principles set out in AS 3600 and related codes. The reason water sits at the top of the list is compounding: a small membrane failure on a planter box or balcony admits water that then corrodes reinforcement, cracks the surrounding concrete, and spreads — so a $20,000 waterproofing problem ignored for five years becomes a six-figure concrete repair.
Remedial projects in Sydney range from roughly $50,000 for a contained balcony or waterproofing repair to $5 million-plus for a full facade or cladding program on a large strata building. Cost is driven by access (scaffold versus rope access), the extent of hidden damage found once the work opens up, and compliance requirements — not by floor area alone.
| Work type | Typical scope | Indicative cost band | Typical duration |
| Balcony / localised waterproofing | Membrane replacement, screed, tiling across a few balconies | from ~$50k | 2–6 weeks |
| Concrete cancer repair | Spalling treatment, reinforcement protection, patch and protective coating | ~$100k+ | 6–12 weeks |
| Roof / flat-roof waterproofing | Membrane renewal across the roof area | mid six figures | 2–5 months |
| Facade / cladding program | Cladding replacement, facade repair, access systems | $1M–$5M+ | 6–12 months |
These are indicative bands to help a committee set expectations, not quotes — the only accurate number comes after an investigation. For a fuller breakdown of the drivers, see our guide to what a remedial program costs. As a reference point, Atomic Projects has delivered more than $20M of remedial work across 100+ Sydney strata buildings, on projects running from around $50k balcony repairs to $5M-plus facade programs such as the Chandos Street facade and cladding program in St Leonards and the Pacific Highway concrete-cancer remediation in Killara.
A single-defect repair can be completed in a few weeks; a whole-of-building facade or cladding program typically runs six to twelve months. The biggest variables are access — scaffold erection and the approvals around it — weather windows for waterproofing, and the extent of concealed damage uncovered once the first areas are opened up.
Most remedial work happens in and around occupied buildings, so programming matters as much as the repair itself. A well-run project stages the work to keep residents' access, parking and amenity, sequences noisy or disruptive tasks into agreed windows, and communicates ahead of each phase. The timeline a committee should trust is the one built after the investigation, not the one offered before it.
Check three things first: registration (Class 2 DBP and a current NSW builder's licence), a remedial-specific track record on comparable strata buildings, and whether the contractor investigates before quoting. A fixed price given without opening up the defect is the clearest warning sign — it usually means the hidden damage reappears later as a variation and a dispute.
Beyond credentials, look at how the contractor handles the parts committees find hardest. Ask how variations are priced, what warranty is offered in writing, and how they stage work around residents. It is also worth being clear early about who actually pays for the work, because the answer shapes both the budget and the special-levy conversation. Atomic Projects backs its remedial work with a written 10-year warranty and an investigation-first approach on every project.
If your building has an engineer's report, a persistent leak, or a cladding notice, a remedial assessment is the sensible first step — it replaces guesswork with a diagnosis and a real scope. You can talk to the Atomic Projects team about a free, no-obligation assessment.
Send photos, the engineer's report, or just the symptoms — whatever you've got. A registered builder reads it and calls you back. No call centre, no obligation.