What Lengths Do RSJ Steel Beams Come In?
RSJ steel beams are commonly supplied in standard stock lengths, with shorter or exact sizes typically achieved by cutting from those stock lengths. In the UK, most suppliers stock RSJs, Universal Beams (UB) and Universal Columns (UC) in a limited number of nominal mill lengths, with a cut-to-length service providing exact sizes for individual projects.
This guide explains the typical RSJ lengths used in UK construction, how cut-to-length supply works, and what buyers should consider before ordering.
Standard RSJ Steel Beam Lengths in the UK
Most RSJ steel beams are rolled at the mill in fixed stock lengths rather than made to order. The most common nominal stock lengths encountered in the UK are:
- 6 m
- 7.5 m
- 9 m
- 12 m
Not every section size is available in every length. Larger and heavier sections are more commonly stocked in shorter standard lengths, while lighter sections may be available up to 12 m depending on mill production and stockholder range.
6 m RSJ Steel Beams: The Most Common Length
The 6 m RSJ (also written as 6m RSJ) is the most widely stocked length in the UK and is the default starting point for most residential and light commercial steel beam supply. A 6m RSJ stock length is long enough to cover the vast majority of domestic spans (typical loft conversions, single-storey extension openings, internal wall removals), short enough to deliver on standard articulated or rigid trucks, and available across almost the full range of UB and UC section sizes.
Cost per metre is also generally most competitive at the 6 m stock length, because it's the volume length stockholders carry most actively.
You can view the full range of available sections in the RSJ steel beams collection.
Are RSJs Always Supplied in Full Stock Lengths?
In practice, RSJs are very rarely used at full stock length on site. Most projects need a specific cut size, and beams are cut to length from a stock length before delivery.
Typical supply scenarios include:
- A 4.2 m beam cut to length from a 6 m stock length
- Multiple shorter beams cut to length from one stock length
- Full-length beams supplied where site access and handling allow
Cutting beams to size before delivery is standard practice, particularly on residential projects where handling long sections on site can be impractical. Specifying an exact cut to length at order stage avoids on-site cutting, reduces material wastage, and allows the supplier to confirm fit against your structural drawings.
Typical Lengths by Section Type
Although RSJs, Universal Beams and Universal Columns follow similar length conventions, availability varies by section type:
| Section type | Typical stock lengths |
|---|---|
| RSJ / Universal Beam (UB) | 6 m, 7.5 m, 9 m, up to 12 m |
| Universal Column (UC) | 6 m, 7.5 m, occasionally 9 m |
| Heavier sections | Commonly 6 m or 7.5 m |
Universal Beams are generally available in longer stock lengths than Universal Columns, particularly in lighter sections. For the difference between UB and UC sections, see our guide on types of steel beams. For section sizing, weights and span tables, see the RSJ steel beam size guide.
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Ordering RSJs Longer Than Standard Stock Lengths
RSJs longer than standard stock lengths are not typically held as regular stock. Where longer spans are required, projects are usually designed around:
- Multiple beams
- Spliced sections
- Alternative structural layouts
Any requirement for non-standard lengths is normally addressed at the structural design stage, rather than by sourcing bespoke rolled sections.
Practical Considerations When Choosing RSJ Lengths
Before ordering RSJ steel beams, buyers commonly consider:
- Delivery vehicle access for long beams
- Handling and lifting constraints on site
- Whether beams are supplied cut to length
- Material wastage from unused offcuts
- Cost variation by length (longer stock lengths and bespoke cuts may price differently to standard 6 m supply)
Longer beams can increase delivery complexity, while cut-to-length beams are often easier to manage on domestic and light commercial sites.
RSJ Lengths and Finishes
Beam length availability is generally independent of surface finish. Both finishes are commonly supplied cut to length from the same stock lengths:
- Mill finish RSJ steel
- Red oxide primed RSJ steel
The choice of finish typically relates to handling, storage and later coating rather than the length of the beam itself. For the difference between the two finishes, see the red oxide RSJ guide.
Relevant collections:
Frequently Asked Questions
What is the most common RSJ length in the UK?
6 m is the most commonly stocked RSJ length in the UK, with 7.5 m and 9 m also widely available depending on section size. The 6 m length covers the majority of residential and light commercial requirements and is the volume length most stockholders actively carry.
Can RSJs be supplied cut to length?
Yes. RSJs are typically cut to length from standard stock lengths to suit project requirements. Most UK suppliers, including Rackerman, offer a cut-to-length service so beams arrive on site at the exact size specified, reducing on-site cutting and offcut wastage.
What size RSJ do I need for a 6 m span?
The correct RSJ section for any given span depends on the loads being carried, end-support conditions and the structural design produced by a qualified engineer. Section size is not determined by span alone. See the RSJ steel beam size guide for span-related context, but specification should always be confirmed by your structural engineer.
Does the cost of an RSJ depend on its length?
Yes. RSJ pricing is typically calculated per metre, so longer beams cost more in absolute terms. Standard stock lengths (particularly 6 m) often offer the best per-metre value because they're carried in volume; cut-to-length supply adds a cutting fee at some suppliers but reduces wastage. For pricing on specific sections and lengths, see the relevant product collection.
Are longer RSJs harder to deliver?
Longer beams may require larger delivery vehicles and additional handling considerations, particularly on restricted-access sites. 9 m and 12 m stock lengths can require a HIAB or crane offload depending on weight and site conditions; 6 m beams are generally manageable with standard delivery vehicles.
Do Universal Columns come in the same lengths as beams?
Universal Columns are often stocked in shorter lengths than Universal Beams, especially in heavier sizes. 6 m and 7.5 m are common UC stock lengths, with 9 m available in lighter sections.
Can steel be cut to length to non-standard sizes?
Yes. Cut-to-length supply allows any size below the stock length to be specified, typically in millimetres. The cut is made from the nearest available stock length, so a 4,250 mm beam would be cut from a 6 m stock length with the offcut either returned or scrapped depending on supplier policy.
Ordering RSJ Steel Beams
RSJs are usually ordered by specifying:
- Section size (depth × width × weight, from your structural engineer's drawings)
- Required cut length
- Preferred finish (mill finish or red oxide primed)
Stock lengths form the basis of supply, with beams cut to length to suit where required.
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Structural Disclaimer
RSJ steel beams must be specified by a qualified structural engineer. Installation is subject to approved designs and building control approval. This article is provided for general guidance only and does not replace professional structural advice.