DIY Projects
Case Study: Loft Conversion Steels — Ridge and Floor Beams
Anonymous UK loft conversion case study covering ridge and floor RSJ planning sizes, sequence, costs and inspection lessons.
Free planning tools & plain-English guides
Your Complete Guide to RSJ Steel Beams
Free calculators, load tables and installation guides for Rolled Steel Joists. Plan your project, then confirm everything with a chartered structural engineer and Building Control.
50+ Practical Guides
8 Free Calculators
UK Focus + EU
Span 4.5m
Load 45 kN
Type Planning
Quick Access Tools
Everything you need for RSJ beam selection and installation
Free RSJ Calculators
Size, load, weight, deflection, span table, padstone, bearing length and cost — free to use
Calculate nowLoad Tables
Complete size charts, span tables, and safe load references for all beam sizes
View tablesDIY Guides
Step-by-step installation, knockthrough, and project guides with expert tips
Read guidesComparisons
RSJ vs alternatives, materials, finishes, and cost analysis for informed decisions
Compare optionsPopular free RSJ calculators
Start with the tool that matches your question — all free, no signup
Free RSJ calculator FAQ
Quick answers if you searched for an RSJ calculator free online
Is the RSJ calculator on RSJ.info free?
Yes. Size, load, weight, deflection, span lookup, padstone, bearing length and cost tools are free to use with no account. They are planning aids only — not a substitute for a chartered structural engineer or Building Control approval.
Which free calculator should I use first?
Most people start with the beam size calculator or span table lookup. Then check deflection and weight before asking for quotes.
Will Building Control accept calculator results?
No. Online results help you brief an engineer and budget the job. Submit stamped calculations for approval.
What size RSJ do I need for a 4 m span?
Many domestic 4 m openings start conversations around 203×133×25 or 254×146×31 — load width changes that. Read the 4 m span guide and run the size calculator with your numbers.
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What Is an RSJ Beam? A Complete Beginner's Guide
New to structural steel? Our plain-English guide explains what RSJ stands for, how rolled steel joists work, common sizes, typical costs, and whether you need a structural engineer for your project.
- What RSJ, UB and I-beam really mean
- Typical sizes and 2026 prices
- Engineer and Building Control requirements
Latest Articles
Expert insights and practical guides
DIY Projects
Case Study: Kitchen Knock-Through with an RSJ (UK Home)
Anonymous UK case study of a kitchen knock-through: span, beam size conversation, timeline, costs and lessons before Building Control sign-off.
DIY Projects
Padstone Size Guide for RSJ Beams: Worked Examples UK
How to size padstones under RSJ bearings with worked examples. Bearing pressure, masonry capacity and common UK padstone dimensions for planning.
DIY Projects
What Size RSJ for a 6m Span? Long Opening Planning UK
RSJ sizing notes for 6 metre domestic spans. Why stiffness dominates, typical UB ranges, weight, cost and engineer requirements.
Costs & Suppliers
How Much to Install an RSJ in the UK? Labour and Total Costs 2026
Typical UK costs to install an RSJ in 2026: labour, temporary works, engineer fees, Building Control and making-good — not just the price of steel.
Costs & Suppliers
RSJ Sizes and Prices UK 2026: Sections, £/m and Project Totals
RSJ sizes and prices for UK projects in 2026. Typical £ per metre by section, delivery notes, and how steel cost compares to full installed totals.
Essential Site Equipment
Professional tools recommended for structural work
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All structural work should be designed by a qualified structural engineer and approved by Building Control. Our guides provide information only and don't replace professional advice.