The Importance of External Above Ground Waterproofing

Balconies, or external living spaces require protection from moisture that can cause costly damage to the balcony’s supporting structure, or any habitable room(s) below.   A correctly installed waterproof barrier must be installed to provide this critical protection.

These External above-ground areas are defined as External Wet Areas that must be provided with a waterproofing system, installed in accordance with “AS 4654.2-2010 – Waterproofing membranes for external above-ground use”.

The risks and consequence of non-compliance to AS 4654.2 leading to waterproofing failures are substantial for both the building, the builder and the waterproofing contractor, and ultimately the homeowner.

The most common failures associated with balcony or external living space waterproofing is incorrect or inadequate detailing of doors and windows that lead from an internal living space to an external living space.

Correct Detailing of Door Entries Leading onto External Waterproofed Areas

Wet-seal’s Technical Team field many queries from Builders and Architects on correct waterproofing requirements for balconies, however queries are most often focused on how to correctly detail to comply with AS 4654.2 Clause 2.8.3 Doors and windows onto external waterproofed areas.

Clause 2.8.3 states the minimum detailing requirements that ensure moisture, water and wind driven rain cannot penetrate the often-seen voids and cavities exposed where door and window cutouts exist during construction.

Below is a guide for achieving compliance for the following 2 scenarios (A & B):

A.   When a sub-sill flashing is included as part of the membrane system – A sub-sill flashing must be provided and must terminate over the top of the membrane that has been installed in accordance with the termination heights in Table A1 (AS4654.2-2010).  A waterstop angle must be installed on the internal side of the door frame, and finish with the height of the internal floor level.  The Door frame must be removed to allow for sub-sill flashing and must reticulate below frame and up the face of the water stop.  See Image 1.

B.   Where the internal and external floor levels do now allow for an upturn in accordance with Table A1, Appendix A. – A waterproof membrane must reticulate from the external floor substrate, across the door opening and terminate vertically to a height that meets the requirements of Table A1 (AS4654.2-2010).  A waterstop angle must be installed on the internal side of the door frame, and finish with the height of the internal floor level.  Door frame must be removed to allow for the installation of the waterproof membrane.  The waterproofing membrane or a water stop must also be installed up to the minimum termination height for the door/window opening reveals (as indicated above in a cyan dashed line).  A waterstop that is installed prior to the door being installed is likely to inhibit the ability to install the door frame.  See Image 2.

Image 1 – Indicative of the waterproofing membrane where the door opening height exceeds the minimum termination height indicated in Table A1 – Appendix A.

Image 2 – Indicative of the waterproofing membrane where the door opening height DOES NOT exceed the minimum termination height indicated in Table A1 – Appendix A.

Correct waterproofing ensures that when finishes and other decorative trims are installed, short and long-term moisture penetration is accounted for. Unless approved as a certified and compliant design, there are no situations where this detailing can be excluded.

If you are unsure of whether your design meets these requirements or for any other advice of a technical nature, Wet-seal’s highly experienced technical team will be happy to take your call. Wet-seal’s Technical Team can be contacted on 1800 025 081 or via email at technical@wet-seal.ws

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