Project: Concrete lintel remediation, occupied residential building
Location: Neutral Bay, NSW
Sector: Residential remediation
Client: Rogers Construction
Services provided: Temporary works engineering, propping design, supply and installation
Equipment used: Legend 50T Modular Propping System, needle beams, Legend Multiprops, steel counterweights, threaded tie rods, sole plates
Project Overview
Rogers Construction engaged Legend Hire to design, supply and install a propping solution supporting a masonry wall and suspended concrete slab so a large concrete lintel could be remediated. Poor external access and the condition of the existing structure ruled out a conventional propping arrangement, and props had to be installed inside occupied apartments. Legend Hire engineered a cantilever needle propping system with steel counterweights, combined with back propping beneath the slab, holding the wall and slab stable for the duration of the remediation works.
The Challenge
The lintel to be remediated carried both a masonry wall and a suspended concrete slab, so the structure above had to be fully supported before any material was removed. Four constraints shaped the design.
Access was poor. There was no viable position outside the building to land a propping tower or establish a reaction point at ground level, which is the conventional approach to supporting a wall above an opening.
The condition of the existing structure limited how loads could be applied.
The apartments were occupied. Any propping inside the building had to be installed and maintained around residents in place, which governed component sizes, handling method and the sequence of works.
With no external reaction available, any needle beam passing through the wall would cantilever – generating uplift at the back span that had to be positively resisted rather than relying on the building’s own weight
Engineering Considerations
The governing condition was uplift, not compression. A cantilever needle carries its load on the outboard span and lifts at the inboard end, so the design was driven by the hold-down force required at the counterweight stacks rather than by the capacity of the props themselves. Counterweight mass and tie-rod arrangement were sized to maintain positive restraint under the full transferred load.
The second consideration was load path continuity. Because the needles reacted against a suspended slab rather than the ground, the reaction had to be traced down through the structure and back propped at each level until it reached a floor capable of carrying it. Back propping was not supplementary here, it was what made the cantilever viable.
Working in occupied apartments governed the installation method. Components were selected and sequenced so they could be carried in and assembled within tenanted spaces, with the work zone isolated and access maintained for residents throughout.
Equipment Used
- Legend 50T Modular Propping System: modular steel beams forming the needle and support frames
- Needle beams: cantilevered through wall openings to pick up the masonry and slab
- Legend Multiprops: back propping the suspended slab beneath the needle arrangement
- Steel counterweights: stacked, tied down with threaded rods to resist cantilever uplift
- Sole plates and packers: distributing bearing loads across existing floor surfaces
The Outcome
The masonry wall and suspended concrete slab remained fully supported throughout the remediation, allowing Rogers Construction to remove and reinstate the concrete lintel safely and without disturbing the structure above. Once the remediated lintel was cured and capable of carrying load, the temporary works were destressed and struck in a controlled sequence, transferring load back onto the permanent structure.
The apartments remained occupied for the duration of the works, and the propping was removed without incident.
Frequently Asked Questions
Counterweighted needle propping supports a wall by passing needle beams through the masonry and resisting the resulting uplift with stacked steel counterweights at the inboard end, rather than relying on a propping tower positioned outside the structure.
A cantilevered needle beam lifts at its back span as it picks up load at the front. Steel counterweights provide a calculated hold-down force that keeps the system positively restrained, which matters most where the existing structure cannot be relied on to provide that restraint.
Component sizes, handling methods and the sequence of works are selected so the system can be assembled in tenanted spaces with the work zone isolated and resident access maintained. The engineered design accounts for the bearing capacity of existing floors carrying the props.
The wall and any structure it carries must be transferred onto temporary works before the lintel is removed – typically needle beams through the masonry, back propping beneath any suspended slab, and a verified load path down to a competent supporting level.