Project: Temporary propping for structural steel column replacement
Location: Rouse Hill, NSW
Sector: Commercial Construction
Client: ADCO
Services Provided: Engineering, Equipment Hire & Installation
Application: Temporary support of roof rafters during structural steel column removal Equipment
Used: Legend 50T Modular Propping System, Tilt Props
Project Overview
ADCO required the existing structural steel columns supporting a roof structure at Rouse Hill to be removed and replaced with new steelwork. Once those columns were taken out of service, the roof rafters above them lost their permanent support and needed an engineered temporary load path to ground for the duration of the works.
Legend Hire’s engineering team designed a temporary propping system to carry the rafter loads throughout column removal. The governing constraint was geometry: the propping had to sit clear of the new steel and its erection path, so the columns could be swapped without the temporary works being repositioned mid-sequence.
The Challenge
The new steel occupied the same zone as the columns coming out, so any prop position fouling a new column or its connections would have to be struck and reinstalled part-way through erection. Removing the existing columns put the full roof rafter load onto the temporary works, with nothing else carrying the roof during the changeover and the props running to the underside of the rafters needed bracing to hold true under load.
The Solution
Legend Hire’s engineering team designed a propping arrangement built around the Legend 50T Modular Propping System, configured to support the roof rafters while the existing structural steel columns were removed and replaced.
Engineered Load Transfer
Prop positions were set out beneath the rafters to establish a continuous temporary load path, transferring roof loads through the modular props and down to prepared bearing points at slab level. Each position was loaded to the engineered design so the rafters remained fully supported from the moment the existing columns were released.
Positioned Clear of the New Steelwork
The prop grid was set out against the new steel drawings rather than the existing structure, keeping every prop position clear of the new column locations, base plate footprints and connection zones. This single decision allowed the propping to remain in place across both demolition and erection, removing the need to strike and reinstall the temporary works mid-sequence. Legend Hire’s 3D design capability supports this kind of clash coordination before equipment reaches site.
Braced for Lateral Stability
Tilt props were installed as bracing to the modular propping, providing lateral restraint and holding the props true under load. The bracing maintained the geometry of the temporary works throughout the works, so the vertical load path stayed intact while demolition and steel erection proceeded around it.
The Outcome
The roof rafters were supported throughout the works, allowing ADCO to remove the existing structural steel columns with the roof structure carried on the temporary works at all times. Because the prop positions were coordinated against the new steel setout, the propping remained in place across both demolition and erection, no props were struck and reinstalled, and no clash-driven rework was required.
The engineered temporary works maintained a controlled load path from the rafters to ground, the structural steel replacement proceeded within the planned sequence, and the works were completed without structural incident.
Equipment Used
- Legend 50T Modular Propping System: Heavy-duty modular propping rated to 50 tonnes, used to establish the temporary load path carrying the roof rafters during structural steel column removal. The modular format allows prop positions to be configured to a specific setout rather than a fixed footprint, which is what made clash-free positioning around the new steel achievable.
- Tilt Props: Adjustable steel props installed as raking bracing to the modular propping, providing lateral restraint and holding the vertical props true under load for the duration of the works.
Frequently Asked Questions
Roof rafters are supported by a temporary propping system that creates an alternative load path to ground. Props are installed beneath the rafters and loaded to an engineered design before the existing columns are released, so the roof structure is carried by the temporary works throughout the removal and remains stable until the new steel takes load.
By setting the prop positions out against the new steel drawings rather than the existing structure. Prop locations are checked against new column positions, base plate footprints, connection zones and the crane erection path before installation. Coordinating the setout this way means the propping can stay in place across both demolition and erection instead of being struck and reinstalled part-way through.
Tilt props are used as raking bracing. Installed against a modular propping arrangement, they provide lateral restraint that holds the vertical props true under load and maintains the geometry of the temporary works. Bracing becomes more important as props extend to greater heights, such as to the underside of a roof structure.
Yes, provided the prop positions have been coordinated against the new steel setout from the design stage. If the temporary works are clear of the new column locations, connections and erection path, the propping can remain loaded through both demolition and erection — avoiding an unsupported condition and removing rework from the program.