Strengthening and Repair for Sunlight House, Manchester — a Grade II-listed adaptive reuse project.
Often described as Manchester’s first ‘skyscraper,’ Sunlight House is a 95-year-old landmark currently undergoing a major transformation. The redevelopment will see upper floors converted into modern Grade A office space, while the former basement swimming pool is being repurposed into a mixed-use entertainment and leisure facility. Main contractor, Myco, has transformed this iconic structure through a meticulous refurbishment of over 165,000 sq/ft, blending modernity with practicality. Dedication to sustainability is highlighted by the installation of MEP & HVAC systems designed to achieve an impressive 4-star Nabers and BREEAM excellence.
Interspan was engaged by Myco to deliver both the design-and-construction strengthening of the atrium roof and the supply and installation of corrosion protection and concrete repairs to basement beams — preserving the building’s heritage character while enabling its new functional use.
Client / Project Team
Client / Main Contractor: Myco
Consulting Engineer: Eckersley O’Callaghan
Territory: SORM
Sector: Building Repurposing (Adaptive Reuse)
Project Duration: April – October 2025
Project Challenges
The 1930s reinforced concrete structure presented significant challenges:
• Low concrete strength and uncertain reinforcement configuration in the atrium slab.
• Insufficient structural capacity for the new loading requirements of the amenity space.
• Corrosion and delamination of concrete-encased steel beams in the basement areas.
A sensitive approach was required to strengthen and repair the structure while preserving its heritage-listed architectural features.
Interspan’s Strengthening and Repair Solution
Atrium Roof Strengthening
Following detailed investigative works — including ground-penetrating radar (GPR), cover-meter surveys, Schmidt hammer testing, and material sampling — Interspan confirmed that the existing slab did not meet the required load capacity for the new rooftop amenity space.
Working in collaboration with Eckersley O’Callaghan and Myco, Interspan’s engineers developed an innovative design using a 25 mm High-Performance Concrete (HPC) overlay anchored to the existing slab with 20 mm galvanised shear studs. To manage construction loads, 3mm bonded steel plates were installed across the slab surface, eliminating the need for temporary propping, whilst protecting the feature-stained-glass lantern.
This thin, durable overlay maintained the architectural integrity of the heritage soffit and provided a smooth, level substrate for subsequent waterproofing and fit-out works.
Scope of Work:
• 150 m of crack injection
• Temporary lifting of services
• Surface preparation and flattening
• Steel plate bonding
• RC infill slabs and temporary works
• HPC overlay installation
Basement Beam Repairs
In the basement, corrosion of concrete-encased steel beams and delamination of surrounding concrete required extensive remedial work.
Interspan undertook corrosion protection and concrete repair works to approximately 200 m of beams, together with patch repairs to slab soffits.
Scope of Work:
• Removal of loose and defective concrete
• Cleaning and corrosion protection of steel beams
• Flowable concrete reinstatement of beam encasements
• Design and installation of temporary works
• Patch repairs to soffit areas
Interspan Specialist Capabilities
Interspan’s specialist capabilities in forensic investigation, in-house design, and comprehensive concrete strengthening and repair solutions enabled the project team to preserve the historic structure while meeting the performance demands of its new use.
The solution delivered improved structural capacity, corrosion protection, and durability — aligning with new regulatory expectations for structural safety, sustainability, and adaptive reuse.
By reinventing existing structures rather than rebuilding, Interspan helps developers and contractors reduce costs, save time, and minimise embodied carbon — extending the life of key heritage assets for future generations.
Interspan will show you how to reduce materials, cost and CO2.
Australia – NSW
United Kingdom & Ireland
Interspan Europe – Strengthening & Repair Division
Interspan Europe has launched its specialist Strengthening & Repair division, responding directly to the reinvention and repurposing of existing structures, which lies at the heart of the London Plan and the EU’s new Energy Performance of Buildings Directive (EPBD).
Interspan uniquely integrates in-house post-tensioning expertise, advanced forensic diagnostics, and cutting-edge strengthening technologies to enable a single-source delivery model trusted by global developers for complex retrofit and reuse projects.
NEW STRUCTURES
The Interspan Group brings unique expertise in post-tensioning, construction methodology, and lifting operations that reduce CO₂ emissions, material usage, and construction program.
EXISTING STRUCTURES
We specialise in helping clients extend the life of concrete structures through advanced repair, strengthening, and carbon fibre solutions. Adaptive reuse projects are a perfect fit for our expertise, helping to minimise waste while delivering safe, modern outcomes that support community growth.
Over the last decade, the Interspan Group has become a market leader in the application of CFRP-strengthening solutions, with notable projects including the award-winning The Space House in London and the Quay Quarter Tower in Sydney.
Quality Assurance
Quality Assurance holds immense significance for Interspan because it impacts the safety of our operatives and future occupants, the long-term durability of our structures, and our client satisfaction and relationships.
Interspan is accredited under CARES APTO1 for the Production and Supply of Post-tensioning Anchorage Systems and is the only post-tension contractor in Australia accredited under CARES APTO4 for the supply and installation of Post-tensioning systems in concrete structures.
Sustainability
Post-tensioning and adaptive reuse are powerful design approaches that reduce material use and embodied carbon—delivering more efficient, resilient, and sustainable structures for the future.
