Drainage Requirements in Canopies

Posted by Jay Stewart on Jul 23, 2024 1:11:16 PM
Jay Stewart
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Drainage Requirements in Canopies
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Are you looking to specify canopies on your next project, but not sure whether to detail a drainage connection? 

In this article, we explain the options available for canopy drainage and discuss the conflicting opinions we often hear from Architects on this issue.

Drainage options on Aurae's canopies

Aurae offers our proprietary canopy products with two options – free draining, or with a downpipe dropper ready for connection to stormwater by a plumber.

Free draining

Draining slot for patio canopy

Free draining canopies have a slot in one, or both, of the front corners. The fall of the canopy is set so rainwater runs towards these points, where it simply falls to the ground below. This makes for a much simpler installation, saving the cost of a downpipe installation and connection to stormwater.

Downpipe dropper

Down pipe dropper for door canopy

All Aurae canopies can be sealed to contain the water, with fall set to one corner where a downpipe dropper is added. The site plumber then must install a downpipe and connect it to the drainage network.

Discover awning and entrance canopy options in this informative blog »

Why some Architects think the NZBC requires downpipes

The NZBC’s E1 says that all drainage systems must be for the purpose of protecting people and other property from damage or injury caused by surface water, and to direct the water to some other, appropriate place. It requires that all drainage systems be accessible for maintenance and that they be built to avoid leakages.

Acceptable Solution E1/AS1, Figure 15, lists the minimum required gutter size, relative to the discharge area and roof pitch. This chart starts from 30m2 of roof coverage but has a callout noting a minimum gutter cross-sectional area of 4000 sq millimetres for anything less than this. This implies that a gutter is needed, and therefore a downpipe connection.

The argument why downpipes are not required

The New Zealand Metal Roofing Manufacturers Association (NZMRM) has 98 members, all roll formers in the roofing industry, and works closely with MBIE to develop acceptable solutions for roofing details. They have developed the ‘NZMRM Code of Practice’ which has become, in their words, a ‘valuable reference document for Territorial Authorities’.

Roofers had the same compliance questions with the drainage of bay windows, so the NZMRM’s acceptable solution says this:

“Minor wall projections such as bay windows and boxed penetrations are treated as part of the wall catchment and are typically excused from requiring spouting and downpipe, provided the plan view surface area of individual projections does not exceed 5m2”.

Aurae has recently heard from an Auckland-based architect who has successfully used this clause to obtain council approval on a free-draining canopy. Aurae agrees that this clause applies to our canopies – and we, therefore, maintain that canopies less than 5m2 do not need a downpipe connection.

Aurae’s free-draining canopies are much more popular than those with downpipes, with hundreds (approaching the thousands) installed nationwide. The additional work and cost of adding a downpipe hardly seems worth the expense when balanced against the amount of water that drips from the free-draining canopies. Not to mention the poor aesthetics of a downpipe right beside your front door.

A note on E2 - waterproofing

Canopy drainage requirements should not be confused with E2 requirements around waterproofing. This NZBC clause is about preventing moisture from entering the building envelope through the roof, claddings and external openings.

Since the fasteners from our canopies are penetrating the wall cladding, steps must be taken to ensure no water can pass via this penetration into the building. Aurae canopies are designed to overflow before the water level reaches the fastener height. In addition, an EPDM (synthetic rubber) washer is added between the canopy and the cladding. When the screws are tightened, the washer is compressed between the cladding and canopy, right around the penetration, effectively sealing it off from the elements. This ensures Aurae’s canopy products comply with NZBC E2 requirements.

Aurae's canopy options

Whether you want a door canopy or a patio canopy, Aurae offers a wide range of options. These include our Horizon tray canopies and the Solaris canopies. For details, refer to the article we have about our canopy options.

Talk to an expert

If you have questions about customisations or are designing an aluminium canopy for an unusual situation, don’t hesitate to contact us. Our team of experts will get back to you and provide the best experience. To learn more, see our entrance canopies brochure.

 

Topics: entrance canopies

 

 

 

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