Waterproofing Best Practice: Preparing for Under Floor Heating

 Under floor heating is becoming increasingly popular in modern bathroom and wet area designs. However, if not correctly planned, it can present significant challenges to compliant waterproofing — particularly at the critical wall/floor junction.

Early consideration and correct detailing are essential to avoid waterproofing failures and non-compliance with Australian Standards.

Why Under Floor Heating Can Be an Issue

The primary risk with under floor heating systems occurs where heating conduits exit the floor and run up the wall. Traditionally, this has often resulted in penetrations through the wall/floor junction flashing below finished floor height.

Many methods have been used in the past to seal these penetrations, most commonly relying on sealants or caulking. However, these methods are not considered a permanent or compliant solution and significantly increase the risk of future failure.

Australian Standard Requirements

 Australian Standard AS 3740:2021 – Waterproofing of Domestic Wet Areas is clear on this matter.

 

Under Clause 4.18 – Floor Heating, the Standard states:

• Under floor heating cables must not penetrate waterproofing membranes
• Under floor heating cables must not penetrate waterstop angles

Failure to comply with these requirements can result in non-compliant installations, increased defect risk, and potential warranty issues.

 

Best Practice Solution

To ensure compliance and long-term performance, Wet-seal recommends that under floor heating conduits are accommodated within the wall structure, rather than penetrating the wall/floor junction.

The following methods are considered best practice:

1. A channel installed into the wall, or
2. A notched and lined slot formed in the wall, large enough to house the conduits

By forming a channel or notch within the wall:

• A continuous wall/floor junction flashing can be installed without interruption
• The waterproofing membrane remains intact and compliant
• Heating conduits are fully contained without penetrating critical waterproofing areas
• Wall tiles can span and conceal the channel once installed

 

This approach eliminates reliance on sealants and significantly reduces the risk of waterproofing failure.

Planning Is Key

Correct provision for under floor heating must be considered before waterproofing works commence. Early coordination between the builder, electrician, and waterproofing contractor ensures the wall detailing can be prepared correctly and avoids costly rework or non-compliant outcomes.

Wet-seal Recommendation

Wet-seal strongly recommends that builders and trades plan for under floor heating at the design and rough-in stage to ensure compliance with Australian Standards and best-practice waterproofing outcomes.

Getting the details right early helps protect the structure, reduces defects, and delivers long-term peace of mind. Please speak with your local Franchisee directly.  Details of how to contact your local Franchisee can be found at Find A Franchisee