Is making a roof exempt from apartment building height a good idea?

In recent years, waterproofing has emerged as one of the most common and costly issues plaguing apartment buildings across New South Wales. As design practitioners, we see the fallout from these failures regularly: leaks in top-floor apartments, costly balcony rectification works, and frustrated residents. Yet while much attention is (rightly) focused on waterproofing products and installation, it’s worth asking a more fundamental question, could better roof design reduce our reliance on waterproofing in the first place?

One major factor is the shift away from traditional pitched roofs in apartment buildings. These days, most new developments feature flat roofs. Why? It comes down to a planning constraint: in NSW, the height of a building is measured to the top of the roof. This means a pitched roof eats into the maximum allowable height and, by extension, potential floor space. For developers, that’s space that can’t be sold, so pitched roofs are often ruled out from the start.

But what if roof structures didn’t count toward building height?

Exempting pitched roofs from the height calculation could open the door to better-performing roof designs. Designers would have the freedom to move water well outside the building envelope, where it belongs, instead of relying entirely on membranes and internal gutters. It’s a simple change that could reduce the risk of water ingress and extend the life of the building.

There would be aesthetic benefits, too. Right now, many of our suburbs are filled with flat-roofed buildings that sit shoulder-to-shoulder at exactly the same height. Allowing for more roof variation would add visual interest and soften the skyline, helping new developments blend more naturally into established neighbourhoods.

Of course, pitched roofs aren’t a silver bullet, good design and workmanship will always be essential. But in a state where waterproofing defects account for a significant portion of building issues, starting by sending rain water far outside the building envelope seems like it would be a good start.