203 x 133 UB25 S355J0 Steel Beam RSJ – Cut to Size

Not sure what size you need? View our RSJ Beam Size Guide — span guidance, section comparisons and planning advice for all standard UK sections.

The 203 x 133 UB25 is an S355J0 structural steel universal beam weighing 25 kg per metre. Available in mill finish or red oxide primer, cut to your exact required length from 1m to 10m using our online cut-to-size calculator. Commonly specified for building openings, mezzanine floors, structural steel frames, domestic and commercial steelwork and secondary beam supports where this section has been confirmed by a structural engineer.

Steel Grade and Specification

Supplied in S355J0 structural steel conforming to BS EN 10025-2, with a minimum yield strength of 355 MPa. The section designation 203 x 133 UB25 refers to a nominal depth of 203.2mm, nominal flange width of 133.4mm and a linear mass of 25 kg/m. Full section properties are published under BS EN 10365:2017.

Available Finishes

Mill finish is supplied as-rolled with natural mill scale — the standard untreated surface straight from manufacture. Suitable for internal structural use where a protective coating will be applied on site.

Red oxide primer provides a shop-applied primer coat offering temporary corrosion protection during transport, storage and installation. Both finishes are structurally identical — the choice depends on your project specification and site requirements.

Cut to Size

Use our cut-to-size calculator above to enter your exact required length in mm. You are charged for the next 100mm increment — for example, 4165mm is billed as 4.2m. Multiple cuts and quantities can be added in a single order. All cuts are +/- 3mm tolerance. Cut-to-length steel is non-returnable unless faulty.

Section Dimensions

Depth (D): 203.2mm  |  Width (B): 133.4mm  |  Web thickness (S): 5.8mm  |  Flange thickness (T): 7.8mm  |  Root radius (R): 7.6mm  |  Depth between fillets (F): 172.4mm  |  Weight: 25 kg/m

Structural Engineer Notice

The 203 x 133 UB25 must be specified by a qualified structural engineer before ordering. Rackerman does not provide structural design advice and cannot confirm suitability for any specific opening, span or load condition. Building regulations approval is required for all structural alterations.

Delivery Information

Lead times are currently 5–10 working days — early bookings get priority. Delivery is kerbside only — our vehicles do not carry HIAB or lifting equipment. Suitable offloading labour or equipment must be arranged on site. Some postcode exclusions apply.

Frequently Asked Questions

What is a 203x133 UB25 steel beam used for?
The 203x133 UB25 is a Universal Beam (UB) weighing 25 kg per metre, used for spanning horizontal loads such as wall openings, lintels and floor supports. At 203mm deep with 133mm flanges, it is commonly specified for domestic extensions, loft conversions, wall removals and light commercial steelwork. It is supplied in S355J0 grade to BS EN 10025-2.

How much does a 203x133 UB25 weigh?
The UB25 weighs 25 kg per metre. A 3m length weighs 75 kg, a 5m length weighs 125 kg, and a 6m length weighs 150 kg. Factor in the beam weight when planning delivery access and lifting on site — beams over 4m typically need two people or mechanical lifting.

Can the 203x133 UB25 be cut to a specific length?
Yes. This beam is supplied cut to your required length from 1m to 10m using the calculator on the product page. Enter the length in mm and the price adjusts automatically. Cuts are to +/- 3mm tolerance. The beam is supplied in mill finish and red oxide.

What is the difference between mill finish and red oxide on the UB25?
Mill finish is the raw steel surface as it comes from the rolling mill — dark grey with mill scale. Red oxide primer is a protective coating applied over the steel to prevent surface rust during storage and transit. Mill finish suits jobs where the beam will be painted, fire-protected or enclosed. Red oxide gives temporary corrosion protection for exposed steelwork awaiting permanent coating.

What is the delivery time for the 203x133 UB25?
Steel beams are delivered on a flatbed lorry within 5-10 working days to mainland UK. The customer is responsible for offloading — beams of this size typically require two people or a forklift. Ensure site access is suitable for a full-size flatbed vehicle.