What is an RSJ in UK construction?

RSJ stands for 'Rolled Steel Joist'. In modern UK construction, these are technically referred to as Universal Beams (UB) or Universal Columns (UC). They are used to support structural loads above openings, such as when removing an internal load-bearing wall.

How do I calculate the weight of a steel beam?

Steel weight is calculated by multiplying the length of the beam in metres by its 'kilograms per metre' (kg/m) rating. For example, a 4-metre 203 x 102 x 23 UB weighs 92.4kg (4m x 23.1kg/m).

Do I need a structural engineer for a steel beam?

Yes. In the UK, Building Regulations require structural calculations for any new steel beam installation. A structural engineer will specify the exact size of the beam, the grade of steel (usually S275 or S355), and the required padstone dimensions.

What is a padstone and why is it needed?

A padstone is a dense concrete block that the steel beam sits on. It spreads the intense point load of the steel beam across a wider area of the brickwork or blockwork below, preventing the masonry from crushing or cracking.

What is an RSJ in UK construction?

RSJ stands for 'Rolled Steel Joist'. In modern UK construction, these are technically referred to as Universal Beams (UB) or Universal Columns (UC). They are used to support structural loads above openings, such as when removing an internal load-bearing wall.

How do I calculate the weight of a steel beam?

Steel weight is calculated by multiplying the length of the beam in metres by its 'kilograms per metre' (kg/m) rating. For example, a 4-metre 203 x 102 x 23 UB weighs 92.4kg (4m x 23.1kg/m).

Do I need a structural engineer for a steel beam?

Yes. In the UK, Building Regulations require structural calculations for any new steel beam installation. A structural engineer will specify the exact size of the beam, the grade of steel (usually S275 or S355), and the required padstone dimensions.

What is a padstone and why is it needed?

A padstone is a dense concrete block that the steel beam sits on. It spreads the intense point load of the steel beam across a wider area of the brickwork or blockwork below, preventing the masonry from crushing or cracking.

Steel Beam Calculator

Estimate weights for UBs and UCs.

Beam Type

Length (m)

Select Section Size

Structural Spec

Safety Tip: Steel beams are incredibly heavy and unforgiving. Never attempt to lift an RSJ alone. Use a **Genie Lift** or **Superlift** for any beam over 60kg to avoid serious back injury or site accidents.

Structural Steel: The Backbone of Your Home

UB vs UC

Choosing the right steel is about more than just dimensions. **Universal Beams (UB)** are 'I' shaped and designed primarily for horizontal spans. **Universal Columns (UC)** are more 'H' shaped and are optimized for vertical compression or where head-height is limited.

Our **steel beam calculator** helps you understand the physical logistics of your project, from the total weight your masonry must support to the equipment needed to lift the beam into place.

Common Sections

152x89x16 UBLightweight Lintels

203x102x23 UBStandard Openings

152x152x23 UCHeavy/Low Headroom

Safety & Handling

A single 4m length of standard 203mm steel weighs nearly 100kg. This is beyond the safe manual handling limit for two people.

For any beam over 50kg, we strongly recommend using a **Genie Lift** or similar mechanical aid. Not only does this protect your back, but it also allows for micro-adjustments when positioning the beam onto the padstones, ensuring a perfectly level finish.

Minimum Bearing

A steel beam must sit on its supports by a certain amount, known as the 'bearing'. In the UK, the standard minimum bearing is **150mm** on each side. If the span is long or the load is heavy, your engineer may specify a larger bearing of 200mm or more.

Dry Packing

Once the steel is in place, any gap between the top of the steel and the masonry above should be 'dry packed' with a semi-dry mortar mix (1:3 cement/sand). This ensures an immediate, non-shrinking load transfer.

Pro Tip: Paint Matters

Always ensure your steel is **primed** (usually red or grey oxide) before installation. If the steel is being used in an area prone to moisture (like a garage or external wall), consider having it **hot-dip galvanised** for permanent rust protection.

Steel & Structural FAQ

Legal Disclaimer

This calculator is for estimation of material weight and handling requirements only. **It does not perform structural calculations.** You MUST consult a qualified structural engineer to determine the safe size and grade of steel required for your specific building project.