The DBP Act and Waterproofing: Regulated Designs Explained

The Design and Building Practitioners Act 2020 is NSW's answer to a decade of apartment defect scandals, and waterproofing sits at its centre, named in the Act itself as a regulated "building element". If you own or manage an apartment, this law reshaped who may design and repair your waterproofing, what paperwork must exist, and who you can hold responsible when it fails. As an architect registered for this work, here is the plain English version, including the part most buildings still have not heard: it applies to repairs, not just new construction.

What the Act does, in one paragraph

For class 2 buildings (apartments, and mixed use buildings with apartments), the DBP Act requires that designs for key building elements be prepared by registered design practitioners who lodge design compliance declarations stating the design complies with the Building Code, and that registered building practitioners build to those declared designs and declare that they did. The regulated building elements are the ones that hurt when they fail: fire safety systems, structure, the building enclosure, key services, and, explicitly, waterproofing. The regime has applied to class 2 since 1 July 2021.

The theory is simple: the defects crisis, in which waterproofing has consistently topped the NSW Government's own strata defect surveys, was substantially a crisis of undocumented, undeclared, uncheckable work. The Act forces the design to exist, on the record, with a registered name attached to it.

The part buildings miss: repairs are covered too

Most committees assume this is a law about new towers. It is not. Building Commission NSW's remedial work guidance is explicit that remedial work, meaning "repair or upgrades on existing buildings, or defect rectification", falls under the regime. Before remedial waterproofing happens on a class 2 building, a registered design practitioner must produce Construction Issued Regulated Designs: location plans, scaled drawings specific to the remedial work, clear demarcation of new versus existing, material schedules and performance specifications. The Commission audits remedial projects against this.

There is a narrow exemption (wet area work arising from a bathroom, kitchen or laundry alteration, in a single dwelling only, that qualifies as exempt development) and an emergency pathway that lets urgent work proceed with the declaration following. But the balcony membrane replacement your building is about to tender? Regulated design work.

Two consequences follow. First, the patch-and-hope quote culture, where a contractor rescopes your waterproofing on a walk-over and starts cutting, is not just risky, it is non-compliant on class 2 buildings. The repair must be designed, by a registered practitioner, before it is built, which is precisely the consultant-then-specialist-builder sequence I run. Second, the paperwork is protective: declared designs and completion documentation are what a future bond claim, warranty action or sale rests on.

For completeness: the extension of these remedial-work requirements to class 3 and 9c buildings (boarding houses, hotels, residential care) has been deferred to 1 July 2028 per the Commission's June 2026 announcement. Class 2 is fully in force now.

Section 37: the duty of care that changed the game

Part 4 of the Act quietly did something enormous. Section 37 gives anyone who carries out construction work, and that includes builders, designers, project managers and developers, a statutory duty to exercise reasonable care to avoid economic loss caused by defects, owed to every owner and every subsequent owner. The Act says an owners corporation suffers economic loss when it bears the cost of rectifying defects. The duty applies whether or not a contract exists, cannot be delegated, and cannot be contracted out of.

And it reaches backwards: the transitional provisions extend the duty to construction work done before the Act, where the loss became apparent within the 10 years before commencement in June 2020 or later. That rolling 10 year window is why owners corporations that thought they had missed every deadline discovered they had a live claim after all. The High Court has since strengthened the position further: in Pafburn (2024), it held that a builder or developer sued under section 37 cannot carve the claim down by blaming the subcontractors it delegated to. Combined with the Home Building Act warranties, the map of avenues is in who pays for waterproofing defects in strata.

My standing caution applies here doubly: these rights are real leverage, and pursuing them is still slow, adversarial and expensive. Buildings should assert them while fixing the building, not instead of fixing it.

What this means practically for your building

• Ask for registration numbers. Anyone designing waterproofing remediation on your class 2 building should be a registered design practitioner, and anyone building it should be registered for the work. Ask, and check.
• Ask where the regulated design is. If remedial waterproofing is being quoted without a declared design behind it, the quote is for non-compliant work, whatever its price.
• Keep every declaration and completion document. They are the building's evidence, for claims, for the regulator, and for every future buyer's due diligence.
• Use the duty of care consciously. If your defects trace to the original construction and the building is within the realistic windows, get advice early, and get the technical evidence (investigation, documented failures) that any claim will stand on.

This Act is also, frankly, why my practice looks the way it does. I am a NSW registered architect, registered under these regimes for class 2, 3 and 9c work, and the Act's whole philosophy, independent, declared design followed by verified construction, is the philosophy of our waterproofing remediation service. If your building needs remedial waterproofing designed the way the law now requires, a Class 2 waterproofing consultation ($660, with a diagnostic site visit) is the place to start.