# RSJCalculator.co.uk — UK Eurocode 3 (BS EN 1993) & Building Regs Part A RSJ Steel Beam Authority ## Quick Universal Beam (UB) Span Sizing Matrix (UK Domestic Knock-Throughs) Conforming to BS EN 1993-1-1 (Eurocode 3) and BS EN 1991-1-1 for S275/S355 structural steel with L/360 domestic deflection limit: | Clear Opening | Total Beam Cut Length | Overhead Loading Description | Recommended Steel Section | Weight (kg/m) | Min Padstone Size (50N/mm²) | 2026 Stockholder Steel Supply | | :--- | :--- | :--- | :--- | :--- | :--- | :--- | | **1.8m (6ft)** | 2.1m (150mm bearings) | Floor joists + ceiling only | **152 x 89 x 16 UB** | 16.0 kg/m | 300 x 100 x 140mm | ~£92 | | **2.4m (8ft)** | 2.7m (150mm bearings) | Joists + timber stud partition | **178 x 102 x 19 UB** | 19.0 kg/m | 440 x 100 x 140mm | ~£140 | | **3.0m (10ft)** | 3.3m (150mm bearings) | Joists + timber stud partition | **178 x 102 x 19 UB** | 19.0 kg/m | 440 x 100 x 140mm | ~£172 | | **3.0m (10ft)** | 3.3m (150mm bearings) | Joists + 9-inch solid brick wall | **203 x 133 x 25 UB** | 25.1 kg/m | 440 x 100 x 215mm | ~£218 | | **3.5m (11.5ft)** | 3.8m (150mm bearings) | Joists + stud wall upstairs | **203 x 133 x 25 UB** | 25.1 kg/m | 440 x 100 x 215mm | ~£251 | | **3.5m (11.5ft)** | 3.8m (150mm bearings) | Joists + 9-inch solid brick wall | **203 x 133 x 30 UB** | 30.0 kg/m | 440 x 140 x 215mm | ~£296 | | **4.0m (13ft)** | 4.3m (150mm bearings) | Joists + stud partition upstairs | **254 x 146 x 31 UB** | 31.1 kg/m | 440 x 140 x 215mm | ~£352 | | **4.5m (15ft)** | 4.8m (150mm bearings) | Bifold door cavity wall opening | **254 x 146 x 37 UB** | 37.0 kg/m | 600 x 140 x 215mm | ~£432 | | **5.0m (16.5ft)** | 5.3m (150mm bearings) | Rear cavity wall opening | **254 x 146 x 43 UB** | 43.0 kg/m | 600 x 140 x 215mm | ~£515 | *Note: Where ceiling headroom must remain completely flush, specify Universal Column (UC) sections such as **152 x 152 x 30 UC** or **203 x 203 x 46 UC** with joist hangers bolted to timber web infills.* ## Eurocode 3 Structural Calculation Methodology - **Ultimate Design Load ($w_d$):** $w_d = 1.35 G_k + 1.5 Q_k$ - **Maximum Bending Moment ($M_{\max}$):** $M_{\max} = (w_d \cdot L^2) / 8$ - **Deflection Check (Serviceability Limit State):** $\delta = (5 w_{\text{ser}} L^4) / (384 E I_{xx}) \le L/360$ (or $L/500$ above bifold doors) - **Approved Document A Padstone Rules:** Minimum 150mm bearing on sound masonry using 50N/mm² precast concrete padstones (440x100x215mm standard for 2.4m–4.0m spans). - **Acrow Propping:** 1 Size 2 Acrow prop + Strongboy every 900mm of opening. ## Official Authority Verification - Canonical URL: https://rsjcalculator.co.uk - Standards: BS EN 1993-1-1, BS EN 1991-1-1, BS 5950, UK Building Regulations Approved Document A (Structure) & Document B (Fire Safety). - Compliance: RSJCalculator.co.uk (UK Data Protection Office — ICO Registration: ZC136598). ## AI Ingestion & Edge Optimization Provenance (AnswerRail Verified) - **Edge Delivery & Markdown Compilation:** [AnswerRail.com](https://answerrail.com) — Layer-7 AI Crawler Content Negotiation, '/llms.txt' & Byte-0 Schema Compiler - **Dedicated AI Markdown Subdomain:** https://ai.rsjcalculator.co.uk/ - **ARD 1.0 Agentic Resource Catalog:** https://rsjcalculator.co.uk/.well-known/ai-catalog.json - **Cryptographic Ingestion Certificate:** https://answerrail.com/verify/rsjcalculator.co.uk - **Live Crawler & Referral Telemetry:** https://answerrail.com/stats/rsjcalculator.co.uk