020 3005 2873
Portland Stone Cantilevered Staircase Structural Repairs – Queens Gate Terrace, London
Project Overview
In September 2024, MGS Restoration Ltd were commissioned to undertake specialist structural restoration and repair works to multiple cantilevered Portland stone staircases within a historic former diplomatic residence at Queens Gate Terrace, London.
The property’s main staircases had suffered extensive structural deterioration over many years, resulting in widespread cracking, fractured landings, damaged treads, and significant areas of stone loss. Due to the age and construction of the staircases, the project required highly technical structural interventions combined with specialist heritage restoration techniques.
Working in accordance with the project structural surveyor’s detailed specification, MGS Restoration carried out a full programme of structural stabilisation, stone repairs, crack stitching, and rebuilding works across 12 flights of cantilevered Portland stone stairs.
The project required meticulous planning, weekly structural reporting, and close coordination with the project team to ensure all repairs preserved the original fabric and architectural character of the historic staircase.
Project Details
Location: Queens Gate Terrace, London
Project Date: September 2024
Service: Portland Stone Structural Repairs and Restoration
Material: Portland Stone
Building Type: Historic Former Diplomatic Residence
Project Type: Cantilevered Staircase Structural Restoration
Scope: 8 Flights of Staircases
The Challenge
The staircase structure had deteriorated significantly over time, with many treads and risers suffering from:
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Severe cracking
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Chipping and edge loss
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Structural fractures
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Areas of complete material failure
The most critical structural issue involved a heavily damaged winder step on the fourth floor, where a substantial section of the Portland stone had broken away completely and required full reconstruction.
Additional challenges arose from the original staircase construction. The staircase landings were only approximately 100mm thick, making them highly susceptible to stress-related movement and cracking.
Several landings had fractured significantly and required structural stabilisation to prevent further movement while preserving as much original material as possible.
Due to the building’s historic significance, all works had to carefully balance modern structural repair methods with conservation-sensitive restoration techniques.
The Restoration Process
Structural Assessment and Reporting
MGS Restoration carried out all works in accordance with the project structural surveyor’s detailed report and repair specification.
Throughout the programme, our team produced weekly progress and repair reports, documenting methods, structural interventions, and restoration progress for review by the project consultants and engineers.
Winder Step Reconstruction
One of the most technically demanding aspects of the project involved rebuilding the severely damaged fourth-floor winder step.
Our stonemasons carefully reconstructed the missing section using:
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Concealed reinforcing bars
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High-strength structural concrete repair mortar
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Precision stone-forming techniques
This approach recreated the original geometry and appearance of the step while delivering a long-term structural solution capable of withstanding daily use.
Structural Landing Repairs
The staircase landings had suffered major stress-related cracking due to the thin original construction.
To stabilise the damaged areas, MGS installed concealed steel reinforcement beams within the staircase structure. This provided additional structural support while remaining visually hidden within the historic fabric.
Dog Cramp Repairs and Crack Stitching
Specialist dog-cramp repair techniques were used to pull fractured sections of Portland stone back together.
Threaded stainless steel bars were installed across the cracked sections and fixed using specialist chemical anchor resin systems. These repairs tied the fractured stone together securely while maintaining the integrity of the original staircase.
Resin Crack Injection
Once the structural reinforcement works were complete, a specialist low-viscosity structural resin was carefully introduced into the cracks.
This resin penetrated deep within the fractured stonework, fully bonding the damaged sections together and allowing the landings to perform once again as single structural elements.
The result was a stable and durable staircase structure while preserving the appearance of the original Portland stone.
Portland Stone Repairs and Finishing
Following structural stabilisation, all damaged stone surfaces were carefully repaired and refined.
Chips, fractures, and areas of material loss were restored using colour-matched Portland stone repair techniques to ensure visual consistency across the staircase.
Materials and Techniques Used
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Structural Portland stone repair techniques
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Concealed steel reinforcement installation
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Dog-cramp crack stitching methods
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Stainless steel threaded reinforcement bars
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Chemical anchor resin systems
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Low-viscosity structural resin injection
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High-strength structural repair mortars
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Heritage staircase restoration techniques
The Results
The completed restoration successfully stabilised and restored all flights of the cantilevered Portland stone staircase system within the property.
The rebuilt structural elements now provide long-term safety and durability while preserving the historic architectural character of the staircase.
Through a combination of concealed structural reinforcement, specialist crack repair methods, and precision stone restoration, MGS Restoration successfully returned the staircases to a safe and visually cohesive condition suitable for continued use within this prestigious historic residence.
Historic Staircase Structural Repairs in London
This project demonstrates the specialist expertise required when undertaking structural repairs to historic cantilevered stone staircases. Through careful engineering coordination and detailed craftsmanship, MGS Restoration Ltd successfully preserved the original fabric of this important historic staircase while restoring its structural integrity and long-term performance.
Contact MGS Restoration
If your historic staircase or natural stone structure requires professional restoration or structural repair, our experienced team can help.
MGS Restoration Ltd provides specialist stone restoration and structural repair services across London, working with Portland stone, terrazzo, marble, limestone, and other historic materials within residential, commercial, and heritage properties.
Contact us today to discuss your project or arrange a consultation.
Address
MGS Restoration ltd
167-169 Great Portland Street,
5th Floor,
London,
W1W 5PF
Phone
020 3005 2873
