Demolition, Excavation and Underpinning, 396 George Street, Sydney CBD

Status: completed May 2025. Client: Venari Projects Commercial. Location: 396 George Street, Sydney CBD. Scope: soft strip, structural demolition, bulk and detailed excavation, and engineered underpinning inside a heritage building on Sydney's busiest street.

Venari engaged Perfect to open up the basement, ground and first floor of an old building on George Street so a new fitout and basement could be built inside it. The shell stayed. Everything else came out, then the ground under it was dug down for a new basement slab and lift pit, with the existing footings underpinned as the dig went deeper. All of it through a single frontage onto George Street, with pedestrians, retail and traffic a few metres away the whole time.

What the job involved

• Soft strip of the basement, ground and first floors: tiling, joinery, ceilings, partitions, glazing and nibs
• Structural demolition of existing slabs, footings and redundant elements, by hand in the sensitive zones
• Bulk and detailed excavation for the new basement slab and lift pit, working around temporary strutting and walers, with back propping removed and reinstated as the dig moved
• Engineered underpinning to the engineer's details: excavation, reinforcement, formwork and concrete pumped from the street with wash outs under strict controls
• Vibration monitoring throughout, tracked by our project engineer, to protect the neighbours and the heritage fabric
• Temporary mechanical ventilation and mostly electric tools to keep the air clean in a confined basement
• Traffic and pedestrian management on the live George Street frontage
• Selected masonry and stone set aside on site for heritage reuse, as directed by the heritage architect

What made it hard

There was no laydown area and no services. The site had no power or water when we arrived, so the first job was generators and a self contained water supply for dust suppression and clean up. Every load of spoil and rubble came out through the building to the footpath and onto a truck in a loading window, because there was nowhere to stockpile and nowhere to park.

The basement envelope set the plant. Compact excavators and a remote controlled demolition robot were the only things that fitted, and they had to work between temporary steel strutting and walers that could not be touched. The sequence was staged so the structure was supported at every step: props in, section out, props reinstated, move on.

Heritage and neighbours set the method. Structural removals near retained fabric were done by hand or with the robot rather than swung at, and vibration was monitored continuously against the engineer's limits. Early starts kept the heavy movements ahead of George Street's peak foot traffic.

Underpinning and the deep dig

As the excavation went below the existing footings, each footing was underpinned in sequence to the engineer's details. Pits were dug by hand to level, reinforcement fixed, formwork set and concrete pumped in from the street frontage, with wash outs contained. The lift pit and the deepest section of the new basement were then taken down to level and blinded ready for the builder's slab.

How it went

The package finished ahead of programme with no lost time injuries. Spoil left site with EPA compliant documentation and tip dockets tracked against every progress claim. ITPs and the quality system were in place before we started and hold and witness points were observed all the way through. Venari gave us a written reference at the end of the job for use on future work.

If you have something similar

Opening up an existing CBD building from the inside is what we do most weeks. If you need a tenancy or basement stripped, cut, propped and dug out with the street still open, have a look at our strip out, demolition and detailed excavation services, or the commercial strip out in Sydney page. Otherwise just get in touch and tell us what you are dealing with.