Waterproofing

-What is it, How should it be done and why is it so important?

Waterproofing of wet areas, such as shower recesses, has consistently been among the most commonly recurring building defect reported to us. We investigate waterpooring issues several times a week. Poor installation practices are commonly a significant cause of waterproofing failure and failure to adhere to accepted industry practice.

Design and Installation

Waterproofing systems should resist:

• Differential movement

• Exposure to cleaning materials and alkalis from cement mortar

• Accommodate expected movement along substrate movement joints

• Protect the surrounding building componets from water

Levels of Risk

Shower Area - High Level of Risk

The floor is required to be waterproofed and drained with adequate fall, walls to be water resistant and junctions and penetrations to be water proofed.

Bathrooms - Medium Level of Risk

Floors of concrete or compressed fibre cement sheet flooring are required to be water resistant and fall to the floor waste.

Areas Adjacent To Baths & Spas - Medium Level of Risk

Floors of concrete or compressed fibre cement sheet flooring are required to be water resistant. Timber floors including particleboard plywood and other materials require waterproofing of the whole floor. Walls are to be water resistant and junctions to be waterproofed. Any penetrations such as horizontal surfaces around such fixtures are to be waterproof and adjacent vertical surfaces to be water resistant.

Walls Adjoining Vessels (e.g. Sink, Basin, Laundry Tubs) - Low Level of Risk

Walls are to be water resistant and junctions waterproof. Typically splashback tiles are suitable for this purpose.

Laundries & WCs - Low Level of Risk

Floors required to be water resistant and where a floor waste is provided the floor shall be graded to the waste. Junctions are to be water resistant.

Materials

Materials used are to be either waterproof or water resistant. They include ceramic tiles, concrete, grout, water rpoof membranes and continous sheeting products.

Design

Shower walls: Shower walls are to be waterproofed to 150mm above shower floor substrate, or 25mm above maximum retained water level. Shower walls are to be water resistant to 1800mm from finished floor level. All internal and external corners and horizontal joints are to be waterproofed within the shower area. Plasterboard joints (outside shower) that extend inside shower areas must be waterproof. Unenclosed shower areas are to be waterproofed to 1500mm from shower. Tap-penetrations are to be sealed. Further, tap washers must be accessible without damaging the seal around tap penetrations.

Floors and horizontal surfaces adjoining an insert bath are to be waterproofed. Where the floor is waterproofed, the tanking of the walls is to be a minimum of 25mm above the finished floor level.

The mebrnae must be flexible, installed with a boind breaker and extend into waste pipes

Performance Requirement

The BCA Performance Requirement for Wet Areas (Part 2.4.1), states,

"To protect the structure of the building and to maintain the amenity of the occupants, water must be prevented from penetrating:

• behind fittings and linings; or
• into concealed spaces, of sanitary facilities, bathrooms, laundries and the like."

Balconies & Decks

Balconies and decks are governed by a seperate standard, although the performance requirements remain the same.

• Substrate material e.g. compressed cement sheet; waterproof ply or concrete
• Min. 50mm set down from finished surfaces at thresholds
• Substrate to have fall to a drainage point
• Sheets screw fixed, not nailed
• Screws countersunk below surface level
• Screw heads sealed over with polyurethane sealant
• Gaps between sheets of 8 -10mm
• 8-10mm gap between decking sheet and walls