HIGH PRIORITYTypical cost: $1,500 – $15,000

Remedial Waterproofing Perth

When original waterproofing fails — whether due to poor installation, age, or Perth's harsh conditions — remedial waterproofing restores the protective barrier and prevents further structural damage.

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Remedial waterproofing is the process of repairing or replacing waterproofing systems that have failed after the original construction. In Perth, this is an increasingly common requirement as homes and buildings from the 2000s and 2010s construction boom reach an age where shortcuts taken during that rapid building period begin to show. Common scenarios requiring remedial waterproofing include leaking bathrooms where the membrane was never properly installed, balconies where UV has degraded the membrane, retaining walls allowing water into below-ground spaces, and roofs with compromised flashing or membrane systems. We connect you with licensed remedial waterproofing contractors across Perth who can diagnose the failure, recommend the right repair approach, and restore effective waterproofing protection.

Signs You Have This Problem

Persistent water leaks despite previous repair attempts

Widespread damp or moisture in multiple areas of the building

Visible membrane failure — blistering, cracking, or delamination

Efflorescence or salt deposits on concrete or masonry surfaces

Water ingress through walls, floors, or roof during rain

Mould growth in areas that should be dry

Common Causes

Poor original waterproofing installation that did not meet AS 3740 standards
Cost-cutting during Perth's rapid construction periods (especially 2005–2015)
Use of inappropriate or low-quality membrane products
Natural membrane degradation due to age and Perth's UV and heat exposure
Building movement on reactive clay soils (more common in Perth's eastern and southern suburbs)
Subsequent renovations or trades damaging existing waterproofing
Inadequate maintenance of sealants, flashings, and drainage systems

What Happens If You Don't Fix This

•Ongoing structural damage from persistent water ingress
•Timber rot in framing, flooring, and structural members
•Corrosion of steel elements and reinforcement
•Progressively worsening mould and indoor air quality issues
•Damage spreading to previously unaffected areas of the building
•Escalating repair costs — early remediation is always cheaper than delayed action

How This Is Fixed

Comprehensive Assessment

A remedial waterproofing specialist conducts a thorough investigation to identify all areas of waterproofing failure. This may include moisture mapping, flood testing, thermal imaging, and destructive testing where necessary.

Remediation Plan

A detailed remediation plan is developed, specifying the membrane systems, repair methods, and sequence of work. For complex projects, this may involve engineering input.

Demolition & Preparation

Failed finishes, tiles, and membranes are removed. The substrate is repaired, and any structural damage (timber rot, concrete spalling) is addressed before new waterproofing is applied.

New Membrane Installation

New waterproofing membranes are applied in strict accordance with AS 3740-2021 and the manufacturer's specifications. All junctions, penetrations, and transitions receive detailed treatment.

Testing & Certification

Flood tests verify the new membrane is watertight. A waterproofing certificate is issued, which is a legal requirement under the WA Building Act for wet area waterproofing.

Reinstatement

Tiles, finishes, and fixtures are reinstated. The contractor provides warranty documentation and maintenance guidance.

Cost Guide: Remedial Waterproofing Perth

Single Wet Area

$1,500 – $5,000

Remedial waterproofing of one bathroom, laundry, or shower. Includes membrane replacement, testing, and basic retiling.

Most Common

Multiple Areas / Balcony

$5,000 – $10,000

Remediation of multiple wet areas or a balcony including structural repairs, new membrane systems, and finishing.

Complex / Whole-Building

$10,000 – $15,000+

Large-scale remedial waterproofing involving multiple levels, complex structural repairs, below-ground tanking, or commercial buildings.

Perth-Specific Notes

Perth experienced a massive construction boom from the mid-2000s through to the mid-2010s, driven by the mining industry. During this period, demand for trades outstripped supply, and some builders and developers cut corners on waterproofing to meet deadlines. Suburbs that saw rapid development during this era — including Baldivis, Ellenbrook, Butler, Byford, and Harrisdale — are now seeing a wave of waterproofing failures as these buildings reach 10–15 years of age. Additionally, Perth's extreme UV accelerates membrane degradation on exposed surfaces, making remedial waterproofing a more frequent requirement than in less UV-intense cities.

Prevention

Avoid future waterproofing failures with proper installation by licensed contractors.

Learn about Bathroom Waterproofing

Licensed contractors only

WA Building Commission · Building Services (Registration) Act 2011

Remedial Waterproofing Perth FAQ

Common questions about this waterproofing issue in Perth

Remedial waterproofing is the repair or replacement of waterproofing systems that have failed after original construction. It involves diagnosing the failure, removing the compromised waterproofing, and installing a new system that meets current Australian standards (AS 3740-2021).

Perth experienced a massive construction boom from the mid-2000s to mid-2010s driven by the mining industry. During this period, demand for trades was extremely high and some builders cut corners on waterproofing to meet deadlines. These shortcuts are now manifesting as leaks and membrane failures as these buildings age.

Yes. Under the Building Act 2011 (WA), waterproofing of wet areas must be carried out by a licensed contractor and a waterproofing certificate must be issued. This applies to remedial work as well as new construction. The certificate confirms the work meets AS 3740 standards.

When properly installed using quality materials by a licensed contractor, remedial waterproofing should last 15–25 years or more depending on the application. UV-exposed areas like balconies may have shorter lifespans. Most reputable contractors offer 7–10 year warranties on their remedial work.

If your home is still within the statutory warranty period (6 years for structural defects in WA), you may be able to claim against the builder for waterproofing failures caused by defective workmanship. Contact the WA Building Commission if your builder is unresponsive.

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