Engineering a unique propping solution for a heritage refurb

The project

In late 2018, Hutchinson Builders began construction of a 37-storey residential tower on the corner of Sydney’s Castlereagh Street. Due for completion in 2021, the project includes the sensitive refurbishment of the heritage-listed Porter House building next door, which will house a luxury boutique hotel.

Coates was initially engaged to design and install hydraulic shoring for the basement retention works during the initial stage of the Porter House project. The company was then contracted to provide temporary propping and hydraulic jacking for the 5-storey building.

The challenge

Built in 1876, Porter House’s timber structural bearers were sagging and suffering from termite damage while the timber columns required upgrading or replacing. To complete the necessary remediation works, the bearers needed to be hydraulically jacked.

“Being a heritage building, a lot of what we’re doing is trying to maintain and preserve what’s here and just add to it. So rather than taking out all the columns, we’re leaving the columns there and strengthening them [with steel supports],” says Elizabeth Abbey, Project Engineer at Hutchinson Builders. Heritage buildings almost always reveal unexpected complexities, Elizabeth adds. “We’ve had to use Coates' expertise for a number of different things we’ve found along the way,” she says.

One such find was an old well in the basement that needed to be preserved due to its archaeological significance. “One of Coates' temporary propping designs completely changed so that we could avoid the well and so did our permanent structure,” Elizabeth says.

Limited machine access to the upper levels of Porter House has been another a key challenge. “We need to be specifying in products that are easily manual handled up stairs,” says Mark Hutchinson, Temporary Works Engineer at Coates.

The solution

The Coates team included a dedicated design engineer who specified a mix of the proprietary Universal Prop System, a modular system capable of propping up to 100 tonnes, and lightweight aluminium Titan props. Hydraulic jacks were also used on the upper levels to jack the bearers.

“On the lower levels where you can use the material hoist, we’ve got the more heavy-duty equipment and as you go up the levels, it’s lighter aluminium equipment such as titan props,” says Mark. The Universal system can be manual handled by the installation team and bolted together on site, which eliminated the need for welding and cutting. “So, from a safety aspect, it’s really advantageous,” says Mark.

Safety in design is always at the forefront at Coates, so where the proprietary system couldn’t be utilised, the team designed specially fabricated structural elements that could also be bolted together in sections in situ.

When columns were removed from the basement to make way for a 3-metre lift pit, the team needed to come up with a solution to support the lower ground floor. Coates designed and installed a unique truss structure on the ground floor using the versatile Universal system, with components ranging from 2-metre props right down to 125mm pieces.

“The Hutchinson team have nicknamed it the ‘Sydney Harbour Bridge’ due to its shape. It’s a really unusual design for us,” says Mark. “The bearers in the basement are actually hung from the underside of this structure.”

The impact

Alongside the safety benefits of the Universal Prop System, the speed and ease of installation made it a cost-effective solution with huge savings for Hutchinson Builders’ programme as all the products were readily available.

Working with one supplier for the design, installation and certification of a propping solution also streamlined processes for the customer and saved valuable time.

“It makes it really easy for us to just have one contact who manages the design within Coates and also manages the install team. It means we only have to organise one person and that takes a lot of the hard work out of it for us,” says Elizabeth.

Collaboration has also been key to the project’s success.

“Coates have been really good in resolving all the challenges by just working through different options with our structural engineer,” says Elizabeth. “If it doesn’t work for the structural engineer, Coates are very quick to think of something new and come back to us with different options.”

Discover how Coates can create a tailored propping solution for your next project. Call (02) 8796 5000 or email technicaldesigns@coateshire.com.au today