Sizing and specification for RSJs and steel beams — wall removals, extensions, loft conversions and open-plan knockthroughs — stamped and accepted by Building Control.
From £400An RSJ (Rolled Steel Joist) is the steel beam used whenever a load-bearing wall is removed or altered — most commonly for a kitchen knockthrough, an open-plan living space, or to create a wider opening for a loft conversion or extension. Getting the beam size wrong isn't a small mistake: too small and the structure above can crack or sag over time; too large and you're paying for steel — and disruption — you didn't need.
Removing a load-bearing wall, creating a wider opening between rooms, supporting a new loft dormer, or forming the opening for a rear or side extension all require a properly calculated steel beam. Building Control will not sign off the work without it.
The size depends on the span, the load above it (roof, floor, walls), and the type of steel. This can only be calculated properly by a structural engineer — guessing or using a generic online table risks an unsafe or over-specified (unnecessarily expensive) beam.
Yes. Even a single steel beam supporting a wall or floor needs a calculation to size it correctly and specify the padstones (the concrete pads that spread the beam's load into the wall below), and Building Control will require this calculation before signing off the work.
Our structural engineering service starts from £400, which covers beam and RSJ sizing, padstone design and a stamped report accepted by Building Control.
In most cases yes — if your architect or builder has provided clear drawings with dimensions, we can size the beam and produce the full calculation package without a site visit.
Send us your drawings and we'll respond within 24 hours with a quote and timeline.
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