Need structural calculations for your project?
We’ll check what’s required for Building Control and prepare clear, buildable calculations and drawings.
What are structural calculations?
Structural calculations are the engineer’s worked-out numbers (and supporting sketches) that prove your building alterations are safe and compliant with the UK Building Regulations (Part A – Structure). They determine the sizes of members (e.g., steel beams, lintels, joists, rafters), the bearing details, connections and padstones so that loads are transferred safely to the foundations.
- Purpose: demonstrate structural safety and compliance for Building Regulations sign-off.
- Output: a calculation report + marked plans/connection details that your builder and Building Control can follow.
- Typical triggers: removing load-bearing walls, rear/side extensions, loft conversions, large openings, dormers, and unusual roofs.
When are structural calculations required?
You’ll usually need an engineer’s design when the works affect the structure. Common cases include:
- Removing a load-bearing wall or chimney breast (beam/lintel design).
- New openings in external walls or for folding/slider doors (steel or engineered lintel sizing).
- Loft conversion: dormer walls/roof, ridge strengthening, floor joists, purlins, trimmers and restraints.
- Single-storey or double-storey extensions (beams, columns, posts, roof members, lateral stability and foundations).
- Vaulted ceilings/rafter ties changed; cathedral roof detailing.
- Garage conversions if altering the opening or bearing arrangement.
- Solar panels on lightweight roofs or heavy finishes needing verification of load paths.
Who can produce them?
Structural calculations should be produced by a suitably qualified and insured professional—typically a Chartered Structural Engineer (MIStructE/CEng) or Chartered Civil Engineer (MICE/CEng) with relevant buildings experience. At Plans Made Easy, we coordinate calculations with your planning/building-regulation drawings so everything aligns for your builder and inspector.
What’s included in a typical calc pack?
- Design brief & assumptions (loads, spans, materials, site constraints).
- Beam/column/lintel sizing (e.g., UB/UC steel, timber or proprietary lintels).
- Connections & bearings (end plate, bolts/welds, padstones, bearing lengths).
- Lateral stability checks (wind, racking walls, roof/diaphragm action, straps).
- Floor/roof design (joist sizes, trimming around openings, rafters, purlins).
- Foundations (verification of existing or design of new where required).
- Marked-up drawings/details for site use and Building Control submission.
- Revisions log if the design evolves after site opening-up or inspector comments.
Process: from brief to Building Control approval
- Survey & information gathering. We review existing plans, photos and any opening-up notes. For complex sites we may visit.
- Pre-design checks. Identify load paths, wall thicknesses, bearing points, and any restrictions (party walls, services).
- Preliminary design. Size principal members and agree any visible implications (e.g., downstand beams) with you.
- Coordination with drawings. We align beam levels, padstone positions and connections with your Building Regulations set and details.
- Calculation report & details. Issued as PDF with marked plans, schedules and notes.
- Submission to Building Control. Either via your council or an Approved Inspector, alongside your inspection plan.
- Queries & revisions. If the inspector asks for clarifications, we respond and update the pack.
Not sure if your idea fits Permitted Development?
We’ll check your project against PD rules and let you know if you need a full planning application.
Costs & timelines
Fees vary with complexity, number of beams, and whether foundations/frames need design. As a guide:
- Single steel/lintel design (e.g., one opening): often a few hundred pounds.
- Typical loft conversion: usually a fixed fee covering joists, dormer, ridge and trimmers.
- Single-storey extension: beam(s), roof members and bearings—typically mid-range.
- Two-storey or complex steel frames: higher due to load paths, stability and connections.
Turnaround is commonly 5–10 working days from complete information, faster if simple and urgent. Allow extra time for opening-up, survey data or where the inspector requests revisions.
Council quirks & local notes
Building Control teams interpret risk slightly differently. Some are happy to take standard beam/lintel tables for small openings; others insist on full calc reports. A few planning case officers (especially on complex planning permission cases) may ask for a structural statement at the planning stage where significant demolition cantilevers or basement works are proposed—most of the time, however, detailed calcs are checked at the Building Regulations stage.
- Milton Keynes & Bucks: for large openings and lofts, inspectors often want clear load paths and restraint details marked on drawings (straps, noggins, lateral ties).
- Beds/Herts: dormer and trimmer details get close scrutiny; show bearing lengths and padstone specs on the plans, not just in the report.
Common projects (extensions, lofts, steel beams)
Extensions
Expect beam sizing over wide bi-fold openings, posts hidden in the reveals, roof beams/rafters, and checks that the remaining existing walls give enough racking resistance. For double storeys, stability (wind frames, sheathed walls or steel bracing) becomes important.
Loft conversions
Design covers new floor joists (often deeper than existing ceiling joists), trimming around the stair, dormer cheeks and front roof, ridge strengthening, and tying the roof to the walls. Where you want a vaulted ceiling, alternative restraint (tie beams/structural ridge) is required.
Steel beams & openings
We size the UB/UC section, specify padstones, and detail connections—e.g., end plates or simple bearings—plus any vertical supports where a wall above remains load-bearing. If multiple steels intersect, a connection/sketch pack is included so the fabricator can quote and the builder can install correctly.
How builders & Building Control use the calcs
- Builders use sizes, levels and connection notes to order steel, set padstones, and build temporary works for safe propping.
- Fabricators quote and fabricate from the steel schedule and connection sketches.
- Building Control checks the report against Part A, ensuring members, bearings and stability measures are adequate. They may ask for clarifications—your engineer should answer promptly.
Interactive FAQs
What do structural calculations look like?
A PDF report with input assumptions, worked design sheets (hand or software), schedules of members, and marked-up drawings showing where each member goes (sizes, bearings, padstones, connections). For simple cases it may be a concise letter with sketches; for larger projects, a full multi-page pack.
When are structural calculations required?
Any time your works affect the structure: removing load-bearing walls, creating large openings, loft conversions, extensions, or altering rafters/joists. Building Control uses the calcs to assess compliance with Part A.
Do architects do structural calculations?
Architects and technicians design the layout and produce drawings; a qualified structural engineer normally designs the members and connections. Some multi-disciplinary practices offer both under one roof—just make sure the structural designer is properly qualified and insured.
How much do structural calculations cost?
Fees scale with complexity and the number of members. A single beam can be a few hundred pounds; a typical loft or single-storey extension is usually a fixed fee in the mid range; complex frames or basements cost more. Ask for a clear scope (what’s included) and whether Building Control queries are covered.
How long do structural calculations take?
Straightforward designs often complete within 5–10 working days from full information. Allow extra time for opening-up, survey data, unusual details, or inspector queries.
Can I do my own structural calculations or use an online calculator?
DIY or generic calculators rarely cover all loading, stability and connection checks and may be rejected by Building Control. For safety and compliance (and insurance), use a qualified engineer.
Are structural calculations needed for Building Control approval?
Yes—where structure is affected, inspectors usually require a calc report. In some very minor cases, standard tables may suffice, but expect to provide proper calcs for most projects.
Which structural analysis software is “best”?
Engineers use a mix—hand checks plus reputable packages—to suit the problem. What matters is competence, appropriate assumptions and coordination with your drawings.
Ready to move your project forward?
Plans Made Easy can prepare compliant plans, manage submissions, and guide you from idea to approval.
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