Waterproofing Consultancy

Internal, External
& Basement Waterproofing
Done Right

Independent waterproofing engineering to AS 3740, AS 4654.1/.2 and BS 8102 — for wet areas, balconies, podiums, planters and below-ground tanking. Inspections, design, certification and NCC Performance Solutions for windows in wet areas.

Book a Waterproofing Inspection 0434 283 703
DEP0001529 Registered Design Practitioner
AIW Australian Institute of Waterproofing Member
Waterproofing engineer witnessing membrane application on a podium deck DBPA & CPEng Registered
Why It Matters

Waterproofing Is the Most Litigated Defect in NSW Strata

Waterproofing accounts for the largest share of strata defect claims, AFCA insurance disputes and Section 80 capital works levies. The work is technically straightforward — but the cost of getting it wrong is high and the supervision is usually thin. Here's where it usually breaks down.

Termination Heights Defaulted to 150 mm

AS 4654.2 Table A1 sets external upturn heights based on the project wind class — 40 mm at N1, 180 mm at N6 / C4. Most balconies in NSW are detailed at "150 mm everywhere" without checking the actual classification, which sometimes means under-spec, sometimes wildly over-spec.

Single Layer Where Dual Is Needed

BS 8102:2022 grades below-ground spaces by consequence of failure. Grade 3 (habitable basements, archives) needs Type A + Type C dual-layer. We see single-membrane tanking specified in Grade 3 spaces routinely — works for a year, fails by year three.

Designed by the Installer

The waterproofer writes the spec, picks the system, signs off the work. No third-party design, no independent inspection. The defect liability period passes, the leak starts, and there's no engineering record of what was actually installed or whether it complied with AS 4858 / AS 4654.2 / AS 3740 in the first place.

What We Do

Waterproofing Consultancy Services

Independent waterproofing engineering across the three main domains — internal wet areas, external decks and below-ground spaces.

Internal Wet Area Design (AS 3740)

Wet area waterproofing design for bathrooms, ensuites, laundries and kitchens — including hob detailing, shower base falls, upturn heights and floor-waste detailing.

  • Bathrooms, ensuites, laundries
  • Shower set-down and fall design
  • Wet-area window Performance Solutions
  • Compliance to AS 3740 / AS 4858

External & Balcony Design (AS 4654.1/.2)

Balcony, podium, planter and exposed-roof waterproofing — with upturn heights re-derived per project wind class, fall design, drainage layout and termination detailing.

  • Balcony & podium membrane selection
  • AS 4654.2 Table A1 upturn verification
  • Planter and landscape detailing
  • Tile-on-screed vs pedestal pavers

Basement & Below-Ground (BS 8102)

Below-ground waterproofing design — Type A (membrane), Type B (integral concrete), Type C (drained cavity) — graded against the BS 8102 risk framework for the building's end use.

  • Grade 1 (car park) to Grade 3 (habitable)
  • Type A / B / C system selection
  • Geotechnical & hydrostatic interpretation
  • Inverted-roof and green-roof tanking

Inspections & Compliance Testing

Staged hold-point inspections, dry-film-thickness verification, witnessed flood tests, water-spray testing to AS 4284, and signed compliance reports for certifier and OC records.

  • Staged hold-point inspections
  • Wet/dry film thickness verification
  • AS 4654.2 / AS 3740 flood tests
  • AS 4284 water-penetration witnessing

Leak Diagnostics & Remediation

Forensic-grade leak tracing on existing buildings — moisture mapping, smoke/water tracer testing, destructive coring — and remedial waterproofing specifications.

  • Non-destructive moisture mapping
  • Smoke / dye tracer leak tracing
  • Targeted core sampling
  • Remedial scope & specification

Performance Solutions & DBPA Declarations

NCC Performance Solutions for windows in wet areas, AAC / proprietary systems outside DtS, and DBPA design compliance declarations for Class 2 / 3 / 9c waterproofing.

  • Wet-area window PS (F1V1)
  • Proprietary system PS pathways
  • DBPA design compliance declarations
  • Lodgement on NSW Planning Portal
Our Process

How We Work

From the architect's set to the final flood test — a clear engineering process.

1

Brief & Scope

Tell us about the project. We'll review the documentation, define a fixed-fee scope of works and turn around a quote — usually within 24 hours.

2

Engineering Work

Our engineers carry out the design, calculation, inspection or assessment to the relevant Australian Standards, NCC provisions and project-specific requirements.

3

Report & Documentation

We deliver clear, signed engineering documentation — drawings, specifications, compliance certificates or reports — built to satisfy certifiers, councils, insurers and the courts.

4

Ongoing Support

Construction support, certifier RFIs, site inspections, post-issue revisions — we stay engaged through to project completion, not just until the document is issued.

Real Projects

Selected Waterproofing Projects

A snapshot of waterproofing engineering we've delivered across new-build and remedial scopes.

Palm Beach residence basement tanking design Basement · Palm Beach

Habitable Basement — Type A + Type C Dual System

A new Palm Beach residence included a Grade 3 habitable basement (cinema and wine room) cut into clay with seasonal groundwater. The original waterproofing scheme was a single Type A bituminous membrane. We re-graded against BS 8102 and specified a Type A + Type C dual system with a drained cavity drainage profile to a sump.

Two years post-completion: no moisture readings above acceptance threshold. Owner's insurance recognised the BS 8102 Grade 3 documentation.
Westmead apartment podium waterproofing Podium · Westmead

1,200 m² Podium — Specified, Inspected, Flood Tested

A new Westmead apartment build required a 1,200 m² landscaped podium over residential car parking. We specified a dual-layer Class III system, designed the drainage and fall layout, and witnessed the membrane installation across four staged inspections including a witnessed flood test of every drainage cell.

Sign-off issued; first independent inspection at year-1 OC defects warranty confirmed no leaks or membrane defects.
Rosebery commercial bathroom Performance Solution for window Wet Area PS · Rosebery

Window in Shower Recess — F1V1 Performance Solution

An architect specified an obscured glass window directly within a shower recess on a high-end residential fitout. AS 3740 DtS prohibits this configuration. We documented a Performance Solution under F1V1 with specific sill detailing, sealed-cavity reveal, and a heightened upturn at the architrave junction.

PS report issued, certifier accepted, window installed as designed. No leak history at 18-month post-handover inspection.
Cronulla balcony remedial waterproofing Remedial · Cronulla

Coastal C2 Balcony — Wind-Class Driven Re-Design

An OC engaged us after a Cronulla beachfront balcony leaked twice in three years following an earlier remediation. Investigation found the contractor had detailed all upturns at 150 mm — AS 4654.2 Table A1 requires 150 mm at N5 / C3 minimum, and Cronulla is C2. The threshold heights were under-spec for the wind class.

Re-detailed with the correct termination heights, dual-layer system, and certified to current Standards. Three-year follow-up: no leaks.
Who We Help

Waterproofing Engineering for Every Stakeholder

Independent of trades and product manufacturers — written for the asset owner.

Owners Corporations & Strata Managers

Common property scopes, capital works planning, defect investigations and compliance certification for Class 2 buildings.

Builders & Developers

Design declarations, Performance Solutions, certification packages and staged inspections — built to satisfy the certifier on the first submission.

Architects & Consultants

Specialist engineering input on facade, waterproofing and structural elements where Deemed-to-Satisfy provisions don't apply.

Homeowners & Investors

Practical engineering advice on renovations, defects and pre-purchase risk assessments — translated out of jargon.

FAQ

Frequently Asked Questions

Why do I need a waterproofing engineer if I have a licensed waterproofer?

Different roles. A licensed waterproofer installs the system; an engineer designs the system and verifies the installation. Most waterproofing failures we see in service trace to gaps the installer was never asked to fill — wrong system for the substrate, termination heights below the wind-class requirement, no third-party witness of dry-film thickness. An independent engineer closes those gaps.

Can you witness a flood test?

Yes. We attend the flood test, witness the damming and water-fill, document the start and end levels with photographic evidence, and issue a signed flood test certificate referencing AS 4654.2 acceptance criteria. The certificate is what insurers and certifiers want on the file.

Do you specify by manufacturer or generic?

Both — depending on the project. For competitively tendered remedial work we usually specify generic performance (e.g. "AS 4858 Class III, minimum X mm DFT, manufacturer to be approved") with three nominated manufacturers as a pricing benchmark. For DBPA-declared new work we typically nominate by manufacturer for full traceability.

How do you decide between Type A, B and C tanking?

Per BS 8102:2022. Type A (barrier membrane) for low hydrostatic head and Grade 1/2 spaces. Type B (integral concrete with admixture or waterstop) where the concrete is the primary water resistance. Type C (drained cavity) where redundancy is needed or the substrate can't be relied on. For Grade 3 habitable spaces we routinely specify Type A + Type C dual systems.

Can you do Performance Solutions for windows in wet areas?

Yes — this is a common scope. AS 3740 DtS prohibits glazing in certain wet-area configurations. We document the PS pathway under F1V1, with project-specific sill detailing, sealed reveal construction and a heightened threshold. Most Performance Solutions issue inside 5–7 working days.

What does a waterproofing inspection actually involve?

Staged inspections at substrate-ready, bond-breaker complete, membrane applied (with DFT or wet-film verification), and final pre-screed. Each stage is photographed and reported, with non-conformances issued in real time so they're fixed before subsequent trades cover the work.

Do you cover all of Australia?

Yes. We have offices in Sydney (Surry Hills), Melbourne (Cremorne) and the Gold Coast (Bundall), and regularly carry out waterproofing work across all states. Regional travel costs quoted separately.

Are you registered to lodge DBPA design declarations for waterproofing?

Yes. Waterproofing is a listed building element under the DBPA Regulation. Our principal engineer is a Registered Design Practitioner (DEP0001529) and lodges declarations on the NSW Planning Portal directly.

Need a Waterproofing Engineer?

Whether it's a new design, a Performance Solution or a forensic leak investigation — tell us about your project and we'll come back with a fixed-fee scope.

Get in Touch