Former Bank Conversion

Former Bank Conversion & Two-Storey Rooftop Extension

This project involved the conversion of a former bank building into a mixed-use development comprising commercial accommodation at ground floor level and newly created residential flats above. The scheme included the addition of a two-storey rooftop extension, significantly increasing the building’s usable floor area while retaining and integrating elements of the original structure.

Simple-Build was appointed to provide geotechnical investigation, structural engineering design, and full structural coordination throughout the project lifecycle.

Project Overview

The existing building was a traditional masonry bank structure with inherent structural limitations typical of early commercial buildings. The client’s objective was to maximise development potential by constructing two additional storeys above the retained building, creating high-quality residential accommodation while maintaining commercial viability at ground floor level.

The project required careful structural assessment, foundation verification, and innovative lightweight construction methods to ensure that the additional load imposed by the rooftop extension could be safely accommodated.

Structural & Geotechnical Engineering Scope

Simple-Build undertook:

• Site-specific geotechnical assessment to evaluate ground conditions and bearing capacity

• Structural appraisal of the existing bank building

• Load path analysis of the retained masonry structure

• Foundation capacity checks and structural strengthening design where required

• Full structural design of the two-storey rooftop extension

• Integration of modern structural systems with existing load-bearing masonry

Given the constraints of the existing structure, minimising additional dead load was critical. To achieve this, the rooftop extension was designed using Cross Laminated Timber (CLT) panels combined with Posi-Joist floor systems, creating a high-strength, lightweight superstructure. This approach reduced foundation demand while improving construction efficiency and programme certainty.

Key Site & Structural Challenges

The primary engineering challenge was working with the limitations of the existing bank structure. Historic buildings of this nature often have:

• Unknown foundation depths and configurations

• Variable masonry strength

• Limited reserve structural capacity

• Complex load transfer paths

Detailed investigations and structural modelling were undertaken to ensure that new loads were appropriately distributed and that no overstressing of the existing fabric occurred.

Careful sequencing and temporary works design were also required during construction to maintain structural stability while integrating the new CLT system above the retained building.

Construction Strategy

The adoption of CLT and engineered timber systems provided multiple benefits:

• Significant reduction in imposed loads on existing foundations

• Improved speed of installation

• High dimensional accuracy

• Reduced site disruption

• Enhanced thermal performance

• The Posi-Joist floor system allowed efficient service integration while maintaining structural depth constraints within the new residential levels.

Outcome

The development successfully achieved:

• Full regulatory approval

• Seamless integration of old and new structural elements

• Completion of construction to programme

• Delivery of high-quality residential units above active commercial space

This project demonstrates Simple-Build’s capability in complex adaptive reuse schemes, rooftop extensions, and the structural transformation of existing buildings into viable mixed-use developments.