Structural Engineer Calculations
Structural Engineer Design and Calculations for Your Project
Structural engineer calculations are the detailed technical designs that specify how your loft conversion, house extension or new build will be constructed safely. They cover steelwork sizes and specifications, timber dimensions, foundation designs, load-bearing wall assessments, floor joist specifications, roof structure calculations, concrete specifications and connection details.
LCCL Construction works with chartered structural engineers from HLS Structural Engineers who prepare all calculations and structural drawings for our projects. Our structural engineers hold professional qualifications including CEng MIStructE (Chartered Engineer, Member of the Institution of Structural Engineers) and HNC in Civil Engineering, with extensive experience in residential structural design across London and Hertfordshire.
Structural calculations are included as a standard part of our design and build service. You do not need to appoint a separate structural engineer — we coordinate everything between our architects, structural engineers and construction team to ensure a seamless process.
Why Do You Need a Structural Engineer?
A structural engineer ensures that every element of your build is structurally safe and compliant with building regulations. Their calculations and drawings are required for building control approval and are used throughout the project by the construction team, building control inspectors and party wall surveyors.
Specifically, structural engineer drawings and calculations are needed for building control application approval, guiding the construction team on exactly how to build each structural element, party wall agreements where structural work affects shared walls or neighbouring foundations, builder costings so that contractors can price the structural materials and labour accurately, and your insurance company who may require evidence that the work has been designed by a qualified structural engineer.
What Our Structural Engineer Calculations Include
For loft conversions, structural calculations typically cover steel beam specifications for supporting the new floor and any load-bearing wall removals, floor joist sizing, roof structure modifications, staircase opening design, and connection details for new steelwork to existing walls. For hip to gable and mansard conversions, additional calculations are required for the new gable wall and modified roof structure.
For house extensions, calculations cover foundation design based on ground conditions, load-bearing wall and beam specifications, floor construction (slab or block and beam), roof structure, lintels over new openings, and connection details between the new extension and the existing house. For new builds, a full structural design is required covering substructure, superstructure, roof, and all load-bearing elements.
Our Structural Engineer Process
Structural engineer calculations can begin once the architectural design is complete and planning permission has been obtained or confirmed. The structural design runs in parallel with the building regulation drawings.
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Step 01 — Site Survey: The structural engineer attends your property to survey the existing structure, assess ground conditions, check existing foundations where visible, measure wall thicknesses, and take photographs. This site visit ensures the structural design is based on the actual conditions of your property, not assumptions.
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Step 02 — Design and Calculations: Using the survey data and architectural drawings, the structural engineer produces detailed calculations and structural drawings. This includes specifying steel beam sizes, timber dimensions, foundation depths and widths, concrete specifications, connection details and any temporary support requirements during construction. All calculations are produced using industry-standard structural engineering software.
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Step 03 — Issue and Coordination: The completed structural drawings and calculations are issued to LCCL Construction, the building control authority and the party wall surveyor where applicable. Our project team reviews the structural design alongside the building regulation drawings to ensure everything is coordinated before construction begins. If building control requests any amendments, our structural engineers respond directly and update the calculations as needed.
Find out more about next step of the process: Party wall agreements >
Back to Building regulation >
Need Structural Engineer Calculations?
Structural calculations are included as part of our design and build service. Book a free consultation call to discuss your project and we will explain exactly what structural work is required for your loft conversion, extension or new build. Call 020 8037 7332, email info@lcclconstruction.co.uk or book online.
Testimonials
From planning to completion, Alex and his team were professional, reliable and delivered an outstanding loft conversion. The whole process was stress-free and the results exceeded our expectations." — KashImaging, Trustpilot
LCCL Construction delivered our rear extension on time, on budget and to a very high standard. The team were professional, communicative and a pleasure to work with throughout." — Alex Gray, Google
Frequently Asked Questions
Q1: Do I need to hire my own structural engineer?
No. If you use LCCL Construction’s design and build service, structural engineer calculations are included and coordinated as part of the project. We work with chartered structural engineers from HLS Structural Engineers who prepare all calculations and drawings. You do not need to find or appoint a separate structural engineer.
Q2: How long do structural calculations take to complete?
Structural calculations typically take 2 to 4 weeks to complete once the architectural design is finalised and the structural engineer has carried out the site survey. The timeline depends on the complexity of the project — a straightforward dormer loft conversion may be completed faster than a large new build. LCCL Construction coordinates the structural design alongside the building regulation drawings to avoid delays.
Q3: What qualifications do your structural engineers have?
Our structural engineers hold professional qualifications including CEng MIStructE (Chartered Engineer, Member of the Institution of Structural Engineers) and HNC in Civil Engineering. They have extensive experience in residential structural design for loft conversions, house extensions, renovations and new builds across London and Hertfordshire.
Q4: Are structural calculations required for all loft conversions and extensions?
Yes. Structural calculations are a legal requirement for virtually all loft conversions and house extensions, as they form part of the building regulation approval process. Even relatively simple projects such as a dormer loft conversion or single-storey rear extension require structural calculations to specify beam sizes, floor joist dimensions and connection details. Building control will not approve the project without them, and your construction team needs them to build safely and correctly.