Revolutionary design opens up use of marginal land.

January 2018

Babbage Consultants have devised an innovative alternative system for building foundations allowing multi-storey construction on marginal land sites.

Employing traditional foundations systems such as pre-loading or piling on these types of land are either cost prohibitive or can take decades for the pre-loading method to be effective.

Babbage’s new foundation system proposes a different approach to this issue by suspending the whole building structure on a platform of lifting beams. These beams are supported by piers on a series of shallow strip foundations. The lifting beams can be used to level the structure using simple hydraulic jacks when required. Even the elevator lift pits are supported by the beam platform so the elevators move with the building. 

Babbage structural engineering principal Dr Victor Lam said the foundation system he designed was potentially a New Zealand first. “I’m not aware of this being done anywhere before” he said. “It’s similar in concept to levelling a timber domestic house, but this is a three-storey apartment block. The whole concept opens up the potential of difficult land – it will potentially allow building on soft land that couldn’t be used previously.”

This new foundation system, currently in Building Consent processing, is being employed on a sea-side 3-storey, 3-stage, 74 unit apartment building development at Richmond Villas retirement village in Thames. 

Malcolm Stapleton, principal of Babbage Geotechnical, said the problem with building on the land was there was variable subsidence across the site, meaning the traditional method of driving foundation piles would be too deep and cost prohibitive.

He said the area comprised alluvial gravels from the nearby Coromandel Ranges, silt and sediment washed into the Firth of Thames from the Hauraki Plains, sand from ancient beaches and the site also contained semi-compacted landfill deposits.
“The potential for liquefaction in the event of an earthquake also had to be addressed in the design” he said.
Previous attempts from other consultants using the traditional method of pre-loading the ground – placing several metres of rock and gravel on top to compact it – had been tried but the ground bounced back after the gravel was removed. When test holes were dug through the land’s thin crust, the material that came out was silt, clay, rotten logs and rubbish. “When the digger dumped a bucket of fill on the ground it just went slop,” he said.

“We’ve used timber floors to reduce the building’s weight, but from the foundation-up it’s a standard three storey apartment building,” he said.
Babbage architects have designed the building to accommodate for potential movement to prevent cracking of the façade and water-tightness problems. 

To view the full page article and more images Click Here

For more information on developing marginal land sites, please contact Dr. Victor Lam.

​09 379 9980