21 Sep 2018

Water penetration at balcony doors

It is no secret that the most commonly occurring and financially impacting building issue we are faced with today is “water penetration” – particularly external balconies and terraces. There are a number of potential sources of water penetration when looking at balconies, and one particular element that is often overlooked or misunderstood by owners is the “balcony door frame”.

Typical water leak at balcony door                   Water leak tracking beneath door

Typical water leak at balcony door                  Water leak tracking beneath door

The National Construction Code (NCC) defines waterproof as ‘the property of a material that does not allow moisture to penetrate through it’. Based on this definition, the balcony door frame and glazing are considered critical waterproof elements, preventing water entry into the building. 

The quality and performance of door frames vary, based on their construction. Whilst we are beginning to see more frequent use of semi-commercial door frames, the majority of strata complexes consist of standard residential frames. These frames do not feature a sub-sill section and have reduced wind and water ratings, presenting a concern in periods of heavy or prolonged, wind-driven rainfall. These frames also rarely, if ever, incorporate a compliant flashing and membrane detail beneath the doors, which further exacerbates the inadequacies of the residential frame. 

Typical residential frame with no sub-sill                     Residential frame with weepholes blocked by sill tiles

Typical residential frame with no sub-sill                   Residential frame with weepholes blocked by sill tiles

These are all factors that need to be considered when preparing a remedial solution, which often necessitates the removal of the existing balcony door. In some circumstances, it is possible to salvage and re-use the existing door frame when re-waterproofing a balcony, however in most situations this is either not possible, impractical or ill-advised. As such, balcony door replacement needs to be considered as a part of every balcony re-waterproofing project.

Typical door profile with sub-sill                 Membrane-door threshold detail (AS4654.2)

Typical door profile with sub-sill                Membrane-door threshold detail (AS4654.2)

Due to the differing construction and exposure of buildings throughout Sydney, each project needs to be assessed individually to ensure a compliant and effective remedial solution. Firstly, the correct door frame needs to be selected to meet the wind and water pressure ratings specified in the relevant Australian Standards. Further to this, the correct detailing of the membrane and sill flashing beneath the door is critical in ensuring a water-tight threshold.