Integrating Roof and Balcony Drainage

A look at the various ways of approaching roof and balcony drainage on high density residential projects.

There are various ways of approaching roof and balcony drainage when designing high density residential projects. The process is the same for recessed or cantilevered balconies. Each balcony is required to have an outlet and an overflow. The outlet will connect to a downpipe, servicing the balconies above and below. Additionally, a roof drain is required which is often incorporated into the balcony drainage system allowing multiple levels to be drained through one downpipe.

Traditionally a downpipe leading from the roof would be designed to penetrate through, or adjacent to each balcony, this would allow the soffit of each balcony to hide a junction for a balcony drain to connect into it. In this situation, Allproof’s uPVC Three Way Connector Junction ( would integrate a 65mm balcony drain (VRTW65) into the downpipe. The downpipe penetration through the balcony would be sealed using an Allproof Balcony Downpipe Flange (BDF100). An overflow drain (VRTW65 OFLOW) is also required which would be covered by an Allproof Soffit Cover on the underside of the balcony. As each balcony is treated as part of a tenancy and included within a fire cell the penetrations would need passive fire protection (PFP).

A more integrated system such as the Allproof Allthrough can be used to reduce complexity. This system integrates the balcony drainage and roof drainage through the same penetration on each balcony removing the need for additional fittings. The Allproof 100mm Allthrough (AT100 O) has been hydraulically tested using an independent NATA accredited laboratory. It is suitable for draining the roof and individual balconies up to 5 litres per second without splash from the downpipe through the Allthrough grating onto waterproof membrane level. This is important in multi-level apartments to ensure water is not discharged onto a balcony under another property title.

Alongside the Allthrough outlet drain, an overflow would have to be provided in a separate penetration to indicate if maintenance is required. This would use the same Allproof base, adding an overflow riser to protect the penetration in the membrane. As with the previous example the overflow outlet can be covered with an Allproof Soffit Cover and both penetrations protected with an Allproof Fire Collar.

Allproof’s roof drains have been hydraulically tested using an independent NATA accredited laboratory to maintain integrity in published testing data. Roof drainage options include small and large diameter bronze drains or the thick gauge PVC Sureflow and VRTW, both available with stainless or plastic grate. All of these are compatible with New Zealand’s leading roof membrane suppliers including their heat applied membranes. 

This coupled with Allproof’s stainless steel downpipes, rainwater heads and scuppers mean specifiers can be confident when selecting Allproof they are getting a fully integrated NZ made drainage system from roof to ground level. Allproof have been supplying NZ made membrane clamp ring drains and accessories for over 30 years, over this period Allproof have collaborated on a vast array of high-profile projects with other industry suppliers, specifiers and trade professionals.

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