Firs Walk, Tewin

Project Overview

• Architect: Argento 
• Project type: Bespoke dwelling 
• Size of project: 4,400 sq/foot 
• Build cost: Circa £1.2m + interiors 
• Location: Firs Walk, Tewin, Welwyn, Hertfordshire 
• Role: Structural and civil engineering design 

Our role 

dbstructural were appointed as the structural and civil engineering designers for this bespoke two-storey family home. Recommended by the architect, we were directly engaged by the client following the receipt of planning permission. 

Project requirements and design process 

The property was designed using traditional load-bearing masonry construction, with a first floor cantilevering up to 600mm over the ground floor to the rear and side elevations. The key structural elements included: 

• Trench fill foundations, with ground conditions comprising pure sand 
• Beam and block flooring at both ground and first floor levels 
• A flat roof using engineered joists designed to support solar PV panels and rooflights 

Key engineering solutions 

• Coordinating complex site conditions 
  A significant challenge was the retention of an existing boundary masonry wall and a 1.5m site level reduction, all within close proximity to the house. Alongside this was the need to manage both foul and surface water drainage effectively. To resolve this, we designed a simple drop-in retaining wall slab, seamlessly tying it into the proposed house footings while maintaining a clear drainage route. 
• Steelwork drawing in Revit for enhanced accuracy 
  The combination of cantilevered floors and roofs, near full-height glazed elevations, and the high loadings from concrete floors made detailing particularly complex. To simplify the build process, we produced a steelwork drawing in Revit and issued a 3D PDF file to the contractor. This provided greater clarity on levels and construction design, significantly easing site coordination for a complicated build. 
• Roof structure optimised for solar panels 
  Given the client’s requirement for renewable energy, the flat roof was designed with engineered joists to accommodate PV panels alongside rooflights.  
• Zig-zag or stepped soffit staircase coordination 
  While the stair itself was designed by others, we played a crucial role in ensuring adequate support at the bearings, coordinating the structural elements to seamlessly integrate the feature staircase. 

Conclusion 

This project showcased the importance of proactive structural engineering, where thoughtful design and modern digital tools like Revit streamlined construction. By integrating structural, site, and solar roof considerations, we successfully delivered a robust yet elegant solution tailored to the client’s vision. 

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