Rectifying box gutter dramas

Rectifying box gutter dramas

Box gutters are becoming well recognised as a problem area for plumbers to design and install. The AHSCA is looking to rectify the issue with targeted training. Deborah Andrich reports. 

In the Summer 2017 edition of Plumbing Connection we highlighted that box gutter rainheads are a problematic aspect of gutter design extending from the designer to the installer and the inspector.

Recognising that there is a lack of professional training available in the marketplace for designers and plumbers to understand the requirements of the building codes and standards to achieve compliance, the Association of Hydraulic Services Consultants Australia (AHSCA) Research Foundation has created a professional training course that gives participants full accreditation in the design of commercial box gutters according to AS/NZS3500.3.

Currently, AS/NZS3500.3 mandates that any overflow measures for box gutters must have the same capacity as the primary roof drainage system. In effect, for a commercial building that may have long roof lines or multiple pitches, all box gutters, downpipes and overflow measures must be able to cope with the deluge from a 1:100 year, fi ve minute duration storm. In order to manage that enormous amount of water, gutter sumps must be employed. Poorly designed or maintained internal gutter sumps can easily become blocked or damaged, or simply not cope with rainfall events that are larger than predicted. This can potentially lead to overtopping of box gutter systems resulting in costly building and contents damage.

“What we are seeing in the industry is many poorly designed internal gutter sumps that don’t abide by the standards or the overflow devices don’t work correctly or both,” says Dr Terry Lucke.

“Many insurance claims for water damage can be traced back to box gutter failures; for the insurance assessor the liability is put back on the plumber or the designer.

“There is a lot of potential for designers and plumbers to misinterpret the Standard and become noncompliant, particularly for the designers in commercial applications. It is the same for domestic plumbers trying to design something to the National Construction Code. The AHSCA Research Foundation training course is designed to simplify the understanding of designing box gutters to be compliant with AS/NZS3500.3, and to help designers to step through it and explain how it should be used properly.

“By undertaking the training courses we are now rolling out, the AHSCA Research Foundation wants to support members by certifying that they are competent in this area of design, and for them to be professionally recognised as such.“

Providing specialist training in box gutter design for commercial buildings not only adds value to the participants’ qualifications, but it also benefits the owners and facility managers of those buildings.

Many in the commercial building space are aware that internal box gutter system design is a problem area and has the potential to cause significant insurance claims and lost time and money to rectify the problem. The advent of such a training course may help to mitigate the risk and lower the insurance premiums by having a designer and plumber with recognised qualifications design the system.

The course structure is aimed at ensuring that the participants are up to speed with current specifications and design. Once completing the assessment, participants are then deemed to be professionally qualified in the design of box gutters to the current standards.

Research is currently underway by the Stormwater Research Group at the University of the Sunshine Coast to develop new Performance-based Design guidelines on behalf of the AHSCA Research Foundation. Current standards specify compliance with a maximum flow rate of 16L/s. The new guidelines will allow designers to design box gutter roof drainage systems to manage flows of up to 100L/s. The second stage of the training will ensure that AHSCA members are fully trained and qualified to use the new Performance-based Design guidelines to design systems capable of up to 100L/sec.

“We have started rolling out the training to State chapter members of the AHSCA and the feedback to date has been extremely positive,” says Terry.

“In the end, the participants will be well respected in the industry allowing them to build on their professional reputation. For building owners and inspectors, there is added confidence in the installation and design of the gutter systems knowing that it has been designed by a qualified professional.”

Moving forward, the AHSCA Research Foundation aims to conduct Stage 1, AS/NZS3500.3 training sessions at least once a year at each of the State Chapters to allow more members to participate in the course and become AHSCA Research Foundation qualified. It is anticipated that the Stage 2 courses will start running in early to mid-2018.

To complement the training package, a software application is soon to be launched that enables AHSCA competent designers to enter the parameters of the gutter systems to produce an AHSCA Research Foundation approved performance based design that can be incorporated into the overall building design. The software program can be found at ht tps:// member-login/

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