UB Section Properties, Weight, Deflection, Moment Capacity & Cost Estimator – 2026
Select a Universal Beam section to retrieve full section properties from the SCI Blue Book (BS EN 10365:2017), then enter the beam span, loading, and supply details to calculate total weight, estimated mid-span deflection, indicative moment capacity, and supply cost. All structural design must be carried out by a chartered structural engineer to Eurocode 3 (BS EN 1993).
The Universal Beam (UB) is the most widely used structural steel section in UK construction — the standard I-section for spanning horizontal loads in beams, rafters, lintels, and floor systems. Sometimes called an RSJ (Rolled Steel Joist) in the UK trade and domestic market — though strictly this term refers to an older, less precise section no longer in general production — the Universal Beam has an I-shaped cross-section with parallel flanges, manufactured by hot-rolling structural steel to the dimensions and tolerances set out in BS EN 10365:2017 (Hot Rolled Steel Channels, I and H Sections — Dimensions and Masses).
UBs are designated by their nominal depth, flange width, and mass per metre — for example, a 406×178×60 UB has a nominal depth of 406mm, nominal flange width of 178mm, and mass of 60 kg per metre of length. The actual dimensions may differ slightly from the nominal: the 406×178×60 UB has an actual depth of 406.4mm and flange width of 177.9mm. The mass per metre designation is the most reliable identifier. Section properties used for structural design are published in the SCI Blue Book (Steel Construction Institute Publication P363) — the standard UK reference for structural steel section data, now published online at steelconstruction.info.
The UK structural steel standard for UBs is BS EN 10025-2, which specifies the material properties for hot-rolled structural steel. The most common grades in UK use are S275 (yield strength 275 N/mm² for sections up to 16mm thick; 265 N/mm² for 16–40mm) and S355 (yield strength 355 N/mm² for sections up to 16mm thick; 345 N/mm² for 16–40mm). S355 allows a smaller, lighter section for equivalent structural performance, typically reducing section weight by 20–30% — often the preferred grade for longer spans and heavily loaded beams where weight and deflection are governing considerations.
Selecting the correct Universal Beam for a given application requires a structural engineer's design to Eurocode 3 (BS EN 1993-1-1) — the mandatory UK structural steel design standard that replaced BS 5950 following the adoption of the Eurocodes. The key design checks for a simply supported UB carrying vertical loads are:
Data from BS EN 10365:2017 and SCI Blue Book P363. All values for the major (y–y) axis unless stated. Yield strength fy = 275 N/mm² (S275, tf ≤ 16mm) or 355 N/mm² (S355, tf ≤ 16mm). Highlighted rows are commonly stocked sizes.
| Designation | kg/m | h (mm) | b (mm) | tf (mm) | tw (mm) | A (cm²) | Iy (cm⁴) | Wel,y (cm³) | Wpl,y (cm³) | iy (cm) | iz (cm) | IT (cm⁴) | Mc,Rd S275 (kNm) | Mc,Rd S355 (kNm) |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 127×76×13 | 13.0 | 127.0 | 76.0 | 7.6 | 4.0 | 16.5 | 473 | 74.6 | 84.2 | 5.35 | 1.84 | 2.85 | 23.2 | 29.9 |
| 152×89×16 | 16.0 | 152.4 | 88.7 | 7.7 | 4.5 | 20.3 | 834 | 109 | 123 | 6.41 | 2.10 | 3.56 | 33.8 | 43.7 |
| 178×102×19 | 19.0 | 177.8 | 101.2 | 7.9 | 4.8 | 24.3 | 1,360 | 153 | 171 | 7.48 | 2.37 | 4.41 | 47.0 | 60.7 |
| 203×102×23 | 23.1 | 203.2 | 101.8 | 9.3 | 5.4 | 29.4 | 2,105 | 207 | 234 | 8.46 | 2.36 | 7.02 | 64.4 | 83.1 |
| 203×133×25 | 25.1 | 203.2 | 133.2 | 7.8 | 5.8 | 32.0 | 2,340 | 231 | 258 | 8.55 | 3.05 | 5.96 | 70.9 | 91.6 |
| 203×133×30 | 30.0 | 206.8 | 133.9 | 9.6 | 6.4 | 38.0 | 2,900 | 280 | 314 | 8.73 | 3.11 | 10.0 | 86.4 | 111 |
| 254×102×22 | 22.0 | 254.0 | 101.6 | 6.8 | 5.8 | 28.0 | 2,840 | 224 | 259 | 10.1 | 2.14 | 4.15 | 71.2 | 92.0 |
| 254×102×25 | 25.2 | 257.2 | 101.9 | 8.4 | 6.0 | 32.0 | 3,415 | 266 | 306 | 10.3 | 2.15 | 6.42 | 84.2 | 109 |
| 254×102×28 | 28.3 | 260.4 | 102.2 | 10.0 | 6.3 | 36.1 | 4,005 | 308 | 353 | 10.5 | 2.16 | 9.57 | 97.1 | 125 |
| 254×146×31 | 31.1 | 251.4 | 146.1 | 8.6 | 6.0 | 39.7 | 4,410 | 351 | 393 | 10.5 | 3.35 | 8.55 | 108 | 140 |
| 254×146×37 | 37.0 | 256.0 | 146.4 | 10.9 | 6.3 | 47.2 | 5,540 | 433 | 483 | 10.8 | 3.37 | 14.5 | 133 | 172 |
| 254×146×43 | 43.0 | 259.6 | 147.3 | 12.7 | 7.2 | 54.8 | 6,540 | 504 | 566 | 10.9 | 3.42 | 22.2 | 156 | 201 |
| 305×127×37 | 37.0 | 304.4 | 123.3 | 10.7 | 7.1 | 47.2 | 7,171 | 471 | 539 | 12.3 | 2.67 | 13.6 | 148 | 191 |
| 305×127×42 | 41.9 | 307.2 | 124.3 | 12.1 | 8.0 | 53.4 | 8,196 | 534 | 614 | 12.4 | 2.69 | 19.6 | 169 | 218 |
| 305×127×48 | 48.1 | 311.0 | 125.3 | 14.0 | 9.0 | 61.2 | 9,575 | 616 | 711 | 12.5 | 2.72 | 29.5 | 196 | 253 |
| 305×165×40 | 40.3 | 303.4 | 165.0 | 10.2 | 6.0 | 51.5 | 8,503 | 560 | 623 | 12.9 | 3.86 | 14.7 | 171 | 221 |
| 305×165×46 | 46.1 | 306.6 | 165.7 | 11.8 | 6.7 | 58.7 | 9,899 | 646 | 720 | 13.0 | 3.88 | 22.4 | 198 | 256 |
| 305×165×54 | 54.0 | 310.4 | 166.9 | 13.7 | 7.9 | 68.8 | 11,700 | 754 | 846 | 13.0 | 3.93 | 35.4 | 233 | 300 |
| 356×171×51 | 51.0 | 355.0 | 171.5 | 11.5 | 7.4 | 64.9 | 14,140 | 796 | 898 | 14.8 | 3.78 | 23.8 | 247 | 319 |
| 356×171×57 | 57.0 | 358.0 | 172.2 | 13.0 | 8.1 | 72.6 | 16,040 | 896 | 1,010 | 14.9 | 3.80 | 33.4 | 278 | 359 |
| 356×171×67 | 67.1 | 363.4 | 173.2 | 15.7 | 9.1 | 85.5 | 19,460 | 1,071 | 1,213 | 15.1 | 3.85 | 56.8 | 334 | 431 |
| 406×178×60 | 60.1 | 406.4 | 177.9 | 12.8 | 7.9 | 76.5 | 21,600 | 1,063 | 1,199 | 16.8 | 3.86 | 30.8 | 330 | 426 |
| 406×178×67 | 67.1 | 409.4 | 178.8 | 14.3 | 8.8 | 85.5 | 24,330 | 1,189 | 1,346 | 16.9 | 3.90 | 43.2 | 370 | 478 |
| 406×178×74 | 74.2 | 412.8 | 179.5 | 16.0 | 9.5 | 94.5 | 27,310 | 1,324 | 1,501 | 17.0 | 3.92 | 59.6 | 413 | 533 |
| 457×191×67 | 67.1 | 453.4 | 189.9 | 12.7 | 8.5 | 85.5 | 29,380 | 1,296 | 1,471 | 18.5 | 4.12 | 31.1 | 405 | 522 |
| 457×191×74 | 74.3 | 457.0 | 190.4 | 14.5 | 9.0 | 94.6 | 33,320 | 1,458 | 1,653 | 18.8 | 4.14 | 45.8 | 455 | 587 |
| 457×191×82 | 82.1 | 460.0 | 191.3 | 16.0 | 9.9 | 104.5 | 37,050 | 1,611 | 1,831 | 18.8 | 4.17 | 62.8 | 503 | 650 |
| 457×191×89 | 89.3 | 463.4 | 191.9 | 17.7 | 10.5 | 114.0 | 41,020 | 1,771 | 2,014 | 19.0 | 4.19 | 84.2 | 554 | 715 |
| 533×210×82 | 82.2 | 528.3 | 208.8 | 13.2 | 9.6 | 104.4 | 47,540 | 1,800 | 2,059 | 21.3 | 4.38 | 37.0 | 566 | 731 |
| 533×210×92 | 92.1 | 533.1 | 209.3 | 15.6 | 10.1 | 117.0 | 55,230 | 2,072 | 2,360 | 21.7 | 4.41 | 57.4 | 649 | 838 |
| 533×210×101 | 101.0 | 536.7 | 210.0 | 17.4 | 10.8 | 129.0 | 61,520 | 2,292 | 2,612 | 21.9 | 4.44 | 78.7 | 719 | 928 |
| 610×229×101 | 101.0 | 602.6 | 227.6 | 14.8 | 10.6 | 129.0 | 75,780 | 2,515 | 2,882 | 24.2 | 4.75 | 51.5 | 793 | 1,023 |
| 610×229×113 | 113.0 | 607.6 | 228.2 | 17.3 | 11.1 | 144.0 | 87,320 | 2,874 | 3,281 | 24.6 | 4.78 | 79.6 | 902 | 1,165 |
| 610×229×125 | 125.0 | 612.2 | 229.0 | 19.6 | 11.9 | 159.0 | 98,610 | 3,222 | 3,676 | 24.9 | 4.81 | 116 | 1,011 | 1,305 |
| 686×254×125 | 125.0 | 677.9 | 253.0 | 16.2 | 11.7 | 159.0 | 118,000 | 3,481 | 3,994 | 27.2 | 5.24 | 75.8 | 1,098 | 1,418 |
| 686×254×140 | 140.0 | 683.5 | 253.7 | 19.0 | 12.4 | 178.0 | 136,300 | 3,987 | 4,558 | 27.6 | 5.27 | 117 | 1,253 | 1,618 |
| 762×267×134 | 134.0 | 750.0 | 264.4 | 15.5 | 12.0 | 171.0 | 150,700 | 4,018 | 4,644 | 29.7 | 5.38 | 72.6 | 1,277 | 1,649 |
| 762×267×147 | 147.0 | 754.0 | 265.2 | 17.5 | 12.8 | 187.0 | 168,500 | 4,470 | 5,163 | 30.0 | 5.40 | 104 | 1,420 | 1,833 |
| 762×267×173 | 173.0 | 762.2 | 266.7 | 21.6 | 14.3 | 220.0 | 205,300 | 5,387 | 6,198 | 30.6 | 5.45 | 186 | 1,704 | 2,200 |
| 838×292×176 | 176.0 | 834.9 | 291.6 | 18.8 | 14.0 | 224.0 | 246,000 | 5,893 | 6,808 | 33.1 | 6.27 | 130 | 1,872 | 2,417 |
| 838×292×194 | 194.0 | 840.7 | 292.4 | 21.7 | 14.7 | 247.0 | 279,200 | 6,638 | 7,640 | 33.6 | 6.29 | 191 | 2,101 | 2,712 |
| 914×305×201 | 201.0 | 903.0 | 303.3 | 20.2 | 15.1 | 256.0 | 325,300 | 7,204 | 8,351 | 35.7 | 6.85 | 168 | 2,297 | 2,965 |
| 914×305×224 | 224.0 | 910.4 | 304.1 | 23.9 | 15.9 | 285.0 | 376,400 | 8,269 | 9,535 | 36.3 | 6.88 | 259 | 2,622 | 3,385 |
| 914×305×253 | 253.0 | 918.4 | 305.5 | 27.9 | 17.3 | 323.0 | 436,900 | 9,511 | 10,940 | 36.8 | 6.91 | 395 | 3,009 | 3,884 |
| 914×419×343 | 343.0 | 911.4 | 418.5 | 32.0 | 19.4 | 437.0 | 625,800 | 13,730 | 15,480 | 37.8 | 9.46 | 568 | 4,257 | 5,496 |
| 914×419×388 | 388.0 | 920.5 | 420.5 | 36.6 | 21.5 | 494.0 | 718,400 | 15,620 | 17,700 | 38.1 | 9.49 | 818 | 4,868 | 6,284 |
Mc,Rd = Wpl,y × fy / 1.00; S275: fy = 275 N/mm² (tf ≤ 16mm), 265 N/mm² (16mm < tf ≤ 40mm); S355: fy = 355 N/mm² (tf ≤ 16mm), 345 N/mm² (16mm < tf ≤ 40mm). These are cross-section resistances — LTB reduction applies to unrestrained spans. Always confirm with structural engineer's Eurocode 3 design.
Steel prices are commodity-driven and can fluctuate significantly month to month. The prices below are mid-range 2026 UK stockholder prices for S275 Universal Beams in standard stock lengths (6m or 12m), delivered to site in South East England. Always obtain live quotes before committing to a budget or contract.
| Section Range | Supply-Only (per tonne, stock length) | Cut to Length Premium | Fabricated (primed, drilled) | Hot-Dip Galvanised Premium | Notes |
|---|---|---|---|---|---|
| Light UBs (up to 203mm depth) | £850–£1,080/tonne | +£50–£80/tonne | +£450–£750/tonne | +£450–£650/tonne | Small sections; typically priced at premium over heavier sections; good stockholder availability |
| Medium UBs (254–457mm depth) | £820–£1,020/tonne | +£50–£80/tonne | +£400–£700/tonne | +£420–£620/tonne | Most commonly used range; best stockholder availability; most competitive pricing |
| Heavy UBs (533–686mm depth) | £810–£1,000/tonne | +£50–£80/tonne | +£380–£680/tonne | +£400–£600/tonne | Transfer beams and long-span primary beams; good availability from major stockholders |
| Very heavy UBs (762mm+ depth) | £800–£980/tonne | +£60–£100/tonne | +£380–£680/tonne | +£400–£600/tonne | Major structural elements; check availability; may require longer lead times from mill |
| S355 premium over S275 | +£20–£50/tonne | — | — | — | Higher strength allows lighter section; net total cost often similar or lower than S275 equivalent |
| Intumescent fire protection (60 min) | +£25–£75/m² section perimeter | — | — | — | Shop-applied; requires primer; confirm Hp/A (section factor) with coating manufacturer |
| Activity | Typical Cost (2026) | Notes |
|---|---|---|
| Delivery (loose beam, SE England) | £120–£250 per load | Confirm access for 13.6m trailer for 12m beams; crane offload may be needed for heavier sections |
| Mobile crane hire (for erection) | £650–£1,500/day (crane + driver) | Required for beams over approximately 200kg (single-piece lift); size of crane depends on load and radius |
| Temporary propping (domestic) | £300–£900 (hire and install) | For domestic wall removal; acrow props supporting upper floors while beam is installed; hire typically 4–8 weeks |
| Padstone supply and fix | £80–£250 per padstone | Concrete or engineering brick padstones at each bearing point; must be sized by engineer to distribute beam reaction |
| Steel fixer / fabricator erection labour | £350–£600/tonne erected | Includes crane signal, bolting, and alignment; complex connections at higher end |
| Domestic RSJ installation (specialist) | £500–£2,500 per beam installed | Includes supply, propping, installation, and padstones; typical domestic lintel beam; price varies with span and access |
| Structural engineer design fee | £200–£1,500 for domestic beam | Essential for Building Regulations compliance; confirms correct section size, padstone design, and connection details |
In the UK trade, RSJ (Rolled Steel Joist) is commonly used interchangeably with Universal Beam — but strictly, RSJs are an older section type with tapered flanges and less precise tolerances, no longer in general production. All modern steel I-sections for structural use in the UK are Universal Beams (UBs) with parallel flanges to BS EN 10365. When a builder or homeowner asks for an "RSJ", they almost certainly mean a UB. Always specify by the full UB designation (e.g. 254×146×31 UB) to avoid ambiguity.
A UB designation such as 406×178×60 UB means: nominal depth 406mm, nominal flange width 178mm, mass 60 kg per metre. The actual dimensions differ slightly (this section is 406.4mm deep and 177.9mm wide). Within the same depth × width family, different mass sections exist — e.g. 406×178×54, ×60, ×67, and ×74 UB all have nominally the same depth and width but different flange and web thicknesses giving different masses and properties.
A UB's cross-section resistance (Mc,Rd) assumes the compression flange is fully restrained. For unrestrained beams — where the compression flange can move sideways between supports — Lateral-Torsional Buckling can reduce the effective moment resistance significantly below Mc,Rd. The LTB reduction factor χLT depends on the LTB slenderness (λ̄LT), calculated from the span between lateral restraints, section properties, and loading pattern. Providing restraint to the compression flange at regular intervals (e.g. by connecting a floor deck or roof purlins) eliminates or reduces LTB. Always check LTB with a structural engineer for unrestrained spans.
For long-span beams and floor beams with sensitive finishes, deflection rather than strength governs the section size. The typical UK deflection limit for floor beams is span/360 for imposed (live) load and span/200 for total load. For beams supporting brittle finishes (plaster, tiles, glass), span/500 may be required. A beam that is structurally adequate in bending may need to be increased by one or more section sizes purely to limit deflection — particularly for spans over 5–6m with significant imposed loads.
Specifying S355 instead of S275 increases yield strength by approximately 29% (355 vs 275 N/mm²), allowing a section approximately 20–30% lighter for the same strength-governed design. The S355 premium is typically only £20–£50/tonne — far less than the value of the weight reduction. For deflection-governed designs, the weight saving is less pronounced because stiffness (E × I) is the same for both grades (Young's modulus E = 210,000 N/mm² for all structural steel). S355 is most beneficial for strength-governed applications: short-span heavily loaded beams, columns, and transfer beams.
UK steel stockholders typically hold UBs in stock lengths of 6m and 12m. Some sections are available in 18m lengths from the mill. Cutting to exact length by the stockholder adds a modest premium (£50–£80/tonne). Having beams cut to exact length on delivery eliminates site cutting, reduces waste, and makes erection safer and more precise. For large orders, sections can also be ordered direct from the mill in exact lengths, typically with 6–10 week lead times.
Eurocode 3 classifies steel sections into Classes 1–4 based on the width-to-thickness ratios of their flanges and web, which govern susceptibility to local buckling. Class 1 sections can form a plastic hinge with sufficient rotation capacity — allowing use of Wpl,y in design. Class 2 can reach full plastic moment but with limited rotation. Class 3 can reach first yield (Wel,y) but not full plasticity. Class 4 sections are susceptible to local buckling before yielding. Most standard UBs in S275 are Class 1 or 2; some slender sections in S355 may be Class 3 — check the Blue Book for section class at each grade.
All structural steel — regardless of grade — has a Young's modulus (E) of 210,000 N/mm² (210 GPa). This means deflection under a given load is the same for S275 and S355 sections of the same dimensions. Stiffness depends on E × I — so to reduce deflection, you must increase I (use a deeper section) rather than change grade. This is why for deflection-governed beams, switching from S275 to S355 does not help unless the same beam weight (and hence the same I) is specified — which provides no benefit at all.
Structural steel loses approximately 50% of its yield strength at 550°C. Building regulations require fire resistance periods of 30–120 minutes depending on building type and element. For domestic beams, 30 minutes fire resistance is typically required. Thin-film intumescent paint (the most common method) provides 30–90 minutes fire protection and can be applied in a workshop (preferred) or on site after erection. The required dry film thickness depends on the section factor (Hp/A — heated perimeter per unit cross-sectional area) and the required fire period — calculate using the intumescent manufacturer's design software.
A Universal Beam for any structural application — including a domestic knocked-through wall — must be sized by a chartered structural engineer. The engineer will calculate the applied loads, design the correct section to Eurocode 3, specify the connection details, design the padstones or bearing plates, and issue calculations for Building Control approval. Engineer fees for a domestic beam design are typically £200–£600 — a small fraction of the project cost and essential insurance against structural failure. Never select a beam size based on rules of thumb, online guides, or previous project experience without engineering verification.
In multi-storey steel frame construction, UBs are frequently designed as composite beams — acting together with the concrete floor slab through mechanical connectors (headed shear studs welded to the top flange). Composite action dramatically increases the effective moment of inertia of the beam (by a factor of 2–3 or more), allowing a significantly smaller and lighter steel section to carry the same load. Composite design is governed by Eurocode 4 (BS EN 1994) and is standard practice in UK commercial and residential flat construction.
UK-produced Universal Beams from Electric Arc Furnace (EAF) steelmaking — using primarily recycled scrap steel — have an embodied carbon of approximately 1,400–1,600 kg CO₂e/tonne. This is significantly lower than primary steel from Basic Oxygen Furnace (BOF) routes (approximately 2,200–2,600 kg CO₂e/tonne). Specifying UK EAF steel, using S355 to reduce section weight, and minimising over-specification are the primary strategies for reducing embodied carbon in structural steelwork. Environmental Product Declarations (EPDs) for specific steel products are available from UK producers on request.
The correct beam size can only be determined by a structural engineer's calculation — it depends on the span, the loads above (floors, walls, roof), the bearing conditions, and any deflection-sensitive finishes. As a very rough guide for domestic residential construction (not a substitute for engineering): spans up to 1.8m typically use a 127×76×13 UB or 152×89×16 UB; 2.4–3.0m spans typically use 203×133×25 UB to 254×146×31 UB; 3.5–5m spans (open-plan kitchen/diner) typically use 305×127×37 UB to 406×178×60 UB; longer spans or heavier loads require progressively larger sections up to 610mm depth or more. Always engage a structural engineer — incorrect beam selection risks structural failure and Building Regulations non-compliance.
Universal Beam supply-only costs in the UK in 2026 range from approximately £820–£1,080 per tonne for standard stock lengths, depending on section size and region. In practical terms for common sizes: a 203×133×25 UB in 3m length costs approximately £20–£30 for the steel alone; a 305×127×48 UB in 6m length costs approximately £150–£200; a 457×191×82 UB in 6m length costs approximately £400–£520. These are supply-only prices — add delivery (£120–£250/load), fabrication if required (+£400–£700/tonne), fire protection if required (+£25–£75/m² of section), and erection costs (£350–£600/tonne). For complete domestic RSJ installation including supply, propping, and fitting, expect to pay £500–£2,500+ per beam depending on size and access.
A Universal Beam designation — for example 406×178×60 UB — describes the section by three numbers and the section type. The first number (406) is the nominal depth in millimetres; the second (178) is the nominal flange width in millimetres; and the third (60) is the mass per metre in kilograms. "UB" identifies it as a Universal Beam. The actual dimensions differ slightly from the nominal — the 406×178×60 UB is actually 406.4mm deep and 177.9mm wide. Within the same depth × width family (e.g. 406×178), multiple mass variants exist (×54, ×60, ×67, ×74) differing in flange and web thickness. The heavier the section, the greater its strength and stiffness — but also its cost and self-weight.
Both are hot-rolled I-sections but with different proportions optimised for different structural roles. A Universal Beam (UB) has a depth-to-width ratio of approximately 1.5–3:1, making it efficient in major-axis bending — ideal for horizontal beams spanning between supports. A Universal Column (UC) has a near-square cross-section (depth ≈ width), making it equally stiff in both axes — ideal for columns carrying primarily axial compression. A UB used as a column is vulnerable to minor-axis buckling because its iz (minor-axis radius of gyration) is much smaller than its iy. For columns, always specify a UC rather than a UB of equivalent mass — the UC provides approximately twice the minor-axis stiffness for the same material weight, giving substantially better column buckling resistance.
Lateral-torsional buckling (LTB) is a failure mode specific to beams where the compression flange moves sideways and twists before the full plastic moment capacity is reached. It occurs in I-sections because the compression flange acts like a slender column that wants to buckle sideways, dragging the rest of the section with it in a combined lateral bending and torsional mode. LTB only occurs in beams where the compression flange is unrestrained between supports — if a floor deck or roof cladding is continuously connected to the top flange, LTB is eliminated for downward loading. The severity of LTB depends on the beam's LTB slenderness (related to the distance between lateral restraints and the beam's torsional properties) and must be checked by a structural engineer to Eurocode 3 Clause 6.3.2 for all unrestrained spans.
Mid-span deflection of a simply supported beam depends on the load pattern, span, and beam stiffness (EI). The standard elastic deflection formulae are: UDL: δ = 5WL³/(384EI); central point load: δ = WL³/(48EI); two equal point loads at third points: δ = 23WL³/(648EI); where W = total load (N), L = span (mm), E = 210,000 N/mm², I = second moment of area (mm⁴). Note that I in cm⁴ must be converted to mm⁴ by multiplying by 10,000 (1 cm⁴ = 10,000 mm⁴). The calculated deflection must not exceed the relevant limit (span/360 for imposed load on floors in most UK practice). This calculator performs this calculation automatically — but always verify with a structural engineer who will also check shear, web bearing, LTB, and connection design.
Technically yes, but it is rarely efficient and generally not recommended. UBs have a much smaller minor-axis radius of gyration (iz) than UCs of equivalent mass — typically 2–5cm versus 5–10cm for UCs. This makes UBs very susceptible to minor-axis column buckling, dramatically reducing their column buckling resistance compared to a UC of similar weight. For example, a 457×191×82 UB has iz = 4.17cm, while a 254×254×89 UC has iz = 6.55cm — the UC has approximately 55% greater minor-axis stiffness for similar mass. For any column application, specify a UC. A UB may be acceptable as a column only where the column is very short (slenderness is very low) or where the column is heavily restrained about the minor axis at close intervals — and even then, always verify with a structural engineer.
Yes — in almost all cases, installing a structural steel beam requires Building Regulations approval. This applies to domestic wall removals, extensions, and loft conversions as much as to commercial structures. The Building Regulations require that structural elements are designed by a competent person (a chartered structural engineer), that calculations are submitted to and approved by Building Control, and that the work is inspected at key stages. For domestic work, a Full Plans application or a Building Notice must be submitted to the local authority or an approved inspector before work begins. Never install a structural steel beam without Building Regulations approval — the consequences include enforcement action, difficulty selling the property, and potential insurance problems.
A padstone is a block of engineering brick, precast concrete, or in-situ concrete placed at each end of a steel beam where it bears on a masonry wall or other support. Its purpose is to spread the concentrated point load from the beam end over a larger area of the wall beneath, preventing local crushing of the masonry. Padstone size must be designed by the structural engineer based on the beam reaction load, the masonry compressive strength, and the plan area required. Typical domestic padstones are 100–215mm deep × 215–440mm plan area, often made from Class B engineering bricks or precast concrete. Never omit padstones from a beam installation — concentrated bearing without adequate load spreading can cause local masonry failure.
For standard UB sections in stock lengths, the main UK steel stockholders include Rainham Steel, Barrett Steel, AJN Steelstock, Metals4U, and numerous regional stockholders. For domestic RSJ supply and installation (including propping and padstones), ask your structural engineer for recommendations, or check Checkatrade or TrustATrader for steelwork installers in your area. For fabricated structural steelwork, use a BCSA member fabricator with BS EN 1090 CE marking — the British Constructional Steelwork Association (bcsa.org.uk) maintains a searchable directory. Always confirm: the section designation matches the engineer's specification exactly; the steel grade is S275 or S355 as specified; and the supplier can provide a mill certificate confirming material conformity to BS EN 10025.
Additional Universal Beam resources UK 2026: Steel Construction Info – Blue Book | BCSA – Find a Fabricator | IStructE – Find a Structural Engineer | British Steel – Sections | BSI – BS EN 1993 (Eurocode 3) | CARES – Steel Certification