Double Storey Side Extension & Loft Structural Design

Enfield, London

Project Overview

Liba Consulting was appointed to deliver the structural engineering design for a double storey side extension and loft structural alterations to a residential property in Enfield, London. The project aimed to significantly increase the usable floor area across all levels of the property, while ensuring full integration with the existing structure and maintaining structural integrity.

Our Role 

We provided a full structural design package, including:

  • Structural calculations for extension and loft work
  • Steel beam and load-bearing structure design
  • Foundation design and verification
  • Lintel design for new openings
  • Timber floor, roof, and loft structure design
  • Structural specifications and construction guidance

All works were carried out in accordance with relevant Eurocodes (EN 1990, EN 1991, EN 1992, EN 1993, EN 1995, EN 1996, EN 1997) and UK Building Regulations.

Key Engineering Challenges

The project involved several structural challenges requiring careful coordination:

  • Supporting new double storey and loft loads on existing and new foundations
  • Integrating new structural elements with the existing masonry building
  • Designing structural openings with adequate support using steel beams and lintels
  • Strengthening floor structures to accommodate loft conversion loads
  • Ensuring stability of the structure during construction stages

Engineering Solutions

Steel Structure Design

  • Designed primary steel beams to support extension and loft loads
  • Engineered members to carry combined loads from floors, walls, and roof
  • Designed connections in accordance with Eurocode 3
  • Ensured adequate bearing using padstones and steel plates

Foundation Design

  • Designed strip foundations to safely support new loads from the extension
  • Verified bearing capacity and utilisation within allowable limits
  • Ensured compatibility with existing foundations and construction sequence

Lintels & Openings

  • Designed lintels for new window and bifold door openings
  • Ensured adequate bearing lengths and load transfer
  • Verified loading from masonry, floors, and roof structures
  • Provided guidance for installation and construction tolerances

Timber & Loft Structure

  • Designed floor and roof structures with timber joists and rafters
  • Strengthened existing structure to support loft conversion loads
  • Specified joists and rafters  
  • Included detailing for ridge beams, wall plates, noggins, and connections
  • Ensured efficient load transfer from loft level into supporting walls and steel elements

Risk Management & Compliance

A structured risk assessment was carried out covering:

  • Foundation and bearing failure risks
  • Masonry wall stability
  • Steel and connection performance
  • Loft structural adequacy and load transfer
  • Temporary stability during construction

Mitigation measures were incorporated into the design and specifications to ensure safe construction and long-term performance.

Outcome

The project delivered:

  • A robust structural solution enabling both extension and loft development
  • Efficient integration with the existing building
  • Compliance with all relevant standards and regulations
  • Clear, buildable details for contractors and approval bodies

Why This Project Matters

This project demonstrates Liba Consulting’s ability to:

  • Deliver complete structural design for multi-level residential developments
  • Integrate extensions and loft conversions within existing buildings
  • Provide practical, buildable engineering solutions
  • Ensure safety, compliance, and cost efficiency

Ready to Discuss Your Project?

Whether you need structural calculations, beam design, support with building regulations, or advice for an extension or loft conversion, we’re here to help. Send us your details and we’ll come back to you with a practical next step.

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