Structural strength required for waterfront redevelopment at Mangonui

A community-led development at Mangonui in Northland’s Doubtless Bay brings 500 metres of boardwalk, two viewing platforms, swimming steps, a new jetty and pontoon, and additional parking to the picturesque coastal town.

A solid walkway designed for minimal-to-no vibration

The design was by Rob Brown of Shorewise Engineering Consultants in collaboration with the Mangonui Community Group, whose brief was to create a cost-effective boardwalk that would unify the town’s popular waterfront, improve safety, and stand up to heavy use.

‘We set the deflection limits to avoid the vibration issues associated with people walking, cycling and running on public boardwalks,’ says Rob. ‘We specified an SG8 pine size that we knew would meet the requirements of the project for strength, cost and deflection limits.’

When United Civil won the tender for construction, they chose Northpine to supply the structural timber for the project. ‘It was right at the time of Auckand’s long COVID lockdown and getting materials was difficult,’ says the project manager at United Civil. ‘We went to see Northpine and they pulled out all the stops to provide the product we needed to get underway.’

‘The timber was high-spec material, very dense, and everything was to be bolted and screwed in. The structural engineers specified 350mm deep joists as part of design, and it creates a very solid structure – people run on it, scooter, cycle and it doesn’t vibrate.’

Structural and decking timbers at bespoke sizes

Northpine supplied their specialist Northbeam range for bearers, joists and decking. ‘Our quote was part of United Civil Construction’s tender and was produced to their requirements,’ says Northpine GM Bruce Larsen. ‘The engineers had specified a number of custom large-dimension products, including big structural members. We had to cut these to fit the brief and we’re one of the few sawmills that will cut bespoke.’

‘It was a tight timetable, exacerbated by the lockdowns. But we made the timetables work, completing production well under normal lead times, to get construction up and going at short notice. It was a big job, so we were flexible and adaptable to get it there on time and to spec.’

Sustainably managed, high-density Northland pine

The properties of mature Northland-grown radiata aided in the creation of these large structural members. ‘Some of the large dimensions, like 350 x 150, are as big as you can go and still meet the standards for structural compliance,’ says Bruce. ‘It’s all about the raw material – denser northern timber can meet the specs.’

Northpine products are BRANZ Appraised and independently verified by Grade Right. Founded in 1999, Northpine is based in Waipu, with a distribution centre at Silverdale which dispatches to building supply merchants around New Zealand.

For more information, email northbeam@northpine.co.nz or call 0508 432 115.

CREDITS

Project: Mangonui Waterfront

Structural engineering: Shorewise Engineering Consultants
Construction: United Civil Construction
Writer: Folio