How much does a steel beam (RSJ) cost to install? (2026 UK prices)

The steel is the cheap part

People expect the beam to be the expensive bit. It rarely is. A single domestic steel section is usually £200–£500 delivered. What you're mostly paying for is the work that makes it safe to put in: propping the floors and walls above, cutting out the opening, building or casting the padstones the beam sits on, lifting the steel into place, packing it tight and leaving it ready for plaster.

• Steel beam supplied: £200–£500 for a single domestic section
• Labour, propping, needles and padstones: £1,200–£3,000 for a typical opening
• Structural engineer's calculations: £350–£1,000 for a domestic beam
• Building Regulations application and inspections: £300–£1,000
• Making good, plastering and flooring joint: £300–£800, often priced separately

Typical prices by job

A kitchen-diner knock-through in a semi, with one beam of around 3–4 m and decent access, sits in the middle of the £1,800–£4,500 range. A doorway-sized opening can come in under £1,500. A full-width rear opening for bifold or sliding doors, usually needing a goalpost frame with posts, pad foundations and longer steels, is typically £5,000–£10,000.

Fit-only steel, where a builder, kitchen fitter or loft converter has the calculations and supplies the beam, is priced on the labour and propping alone. About half our work is fit-only.

What pushes the price up

Span, load and access. A longer opening needs a heavier beam, and a wall carrying two floors and a roof needs more temporary works. A beam that can't be walked in through a door has to be lifted in by more people or a genie lift, or spliced from bolted sections. Solid stone walls, common in older Pennine and Lakeland houses, are thicker and slower to cut than brick.

Services in the wall, such as gas, water, electrics and soil pipes, have to be moved by the right trade before the wall comes out. Fire protection to the steel, usually plasterboard boxing or intumescent paint, is required where Building Regulations call for it.

How to compare two quotes

Make sure both quotes are for the same calculations and the same beam, and check whether the engineer, building control, padstones, fire protection and making good are included or left out. A quote that is £800 cheaper and leaves out the engineer and building control isn't cheaper at all.