Removing a load-bearing wall is one of the most common structural alterations in UK domestic renovation — creating open-plan kitchen-diners, widening hallways, or building out into a garage. In almost every case the load previously carried by the wall must be transferred to a steel beam spanning between new or upgraded supports. Getting the specification wrong risks immediate structural failure or long-term settlement that can be costly to remediate.
No beam sizing in a load-bearing context should be attempted without a structural engineer’s calculations. This guide explains the process, the terminology, the typical specifications, and the costs so you can manage the project with confidence.
Terminology: RSJ, UC, UB and What They Mean
RSJ (Rolled Steel Joist) is the colloquial term most homeowners and tradespeople use for any structural steel beam in a residential context. Technically, the RSJ section with its tapered flanges has largely been superseded in modern practice by:
- UB (Universal Beam) — a parallel-flanged I-section primarily designed to resist bending. This is what most domestic wall-removal beams are: the wide horizontal flanges carry tension and compression, and the vertical web resists shear. Sizes run from 127×76×13 UB (a small beam for modest spans) up to 914×419×388 UB for heavy commercial loads.
- UC (Universal Column) — a square-proportioned I-section designed primarily for axial compression. Used as padstone supports or in portal frames, not typically as a spanning beam.
The section designation reads as depth × flange width × weight per metre. A 203×102×23 UB is 203mm deep, 102mm wide, and weighs 23 kg per metre run.
When Is a Steel Beam Required?
A structural steel beam is needed whenever a load-bearing element is removed or interrupted and the load above must be re-routed. Common domestic situations include:
- Removing a ground-floor party wall segment or internal load-bearing wall to create open-plan living space
- Creating a wider opening in a load-bearing wall (beyond what a standard steel lintel can span economically)
- Loft conversions where a new ridge beam or purlin is needed to convert a hip roof or to support new floor joists
- Garage conversions where the garage door opening needs to carry first-floor load above
- Basement excavations and underpinning where the ground floor structure must be temporarily or permanently supported
The Structural Engineer: Non-Negotiable
A structural engineer must size the beam for every load-bearing application. This is not optional and is not a task for the builder, no matter how experienced. The engineer calculates:
- The load path above the beam (floor loads, wall loads, roof loads)
- The required bending moment and shear capacity
- The required beam section (using standard load tables or software)
- The padstone specification (to spread the point load into the supporting masonry)
- Any lateral restraint requirements
Expect to provide the engineer with the wall location, the proposed opening span, the floors and roof above, and any unusual loads (water tanks, heavy stonework, etc.). Most engineers will want to visit the site for a domestic residential calc; some will work from drawings and photographs.
Building Regulations
All load-bearing structural alterations require Building Regulations approval under Approved Document A (Structure). You have two application routes:
Full Plans application: you submit structural drawings and engineer’s calculations in advance. The Building Control officer approves them before work starts. This is the preferred route as it gives certainty, and is required by most mortgage lenders and buyers’ solicitors.
Building Notice: you notify Building Control before work starts but do not submit drawings. An inspector visits at key stages. Faster to initiate but riskier — the inspector can require changes during construction that prove costly.
In either case, a structural completion certificate should be obtained once the work is passed. Without it, the alteration cannot be evidenced when you sell the property and the buyer’s solicitor will almost certainly require retrospective sign-off.
Typical Beam Sizes for Domestic Spans
These are indicative examples only. Actual specification requires engineering calculations.
| Situation | Span | Typical beam section | Notes |
|---|---|---|---|
| Internal door/opening widening | 1.2–1.8m | 127×76×13 UB or 152×89×16 UB | May be structural steel lintel equivalent |
| Kitchen-diner wall removal | 2.5–3.5m | 178×102×19 UB to 203×102×23 UB | Most common domestic beam |
| Large open-plan span | 3.5–5.0m | 203×133×25 UB to 254×146×31 UB | Padstone and column loads increase |
| Garage front wall, first floor above | 2.4–4.0m | 203×102×23 UB to 254×102×22 UB | Point loads from first-floor joists |
| Loft ridge beam (hip-to-gable conversion) | 5.0–8.0m | 254×146×31 UB to 305×165×40 UB | Depends on roof pitch and purlin loads |
Padstones
A padstone distributes the concentrated point load at each end of the beam into the masonry wall beneath. Without a padstone, the beam bearing area is too small and the masonry can crush or split. Padstones are typically:
- Engineering brick: Staffordshire Blue or similar, three courses (65mm each) minimum, set in 1:3 cement mortar — cost-effective and standard for most domestic applications
- Precast concrete: 215×102mm footprint as a minimum (engineer-specified), often used where the pocket in the wall is too tight for brick courses
The engineer specifies the padstone dimensions based on the bearing stress calculation. A common misconception is that any hard brick will do; dense engineering bricks with a compressive strength of 50 N/mm² or above are required, not standard facing bricks.
Temporary Propping
Before any load-bearing wall can be opened up, the load above must be transferred to temporary props and spreader beams (whaling boards). The propping sequence must be planned and supervised; collapsing a propped floor is a serious safety incident. Acrow props are hired at approximately £20–50 per prop per week; a typical domestic job requires four to six props on two floors.
Propping must extend to a sound structural floor — propping onto a chipboard floor without spreaders will punch through. The propping engineer or an experienced builder familiar with structural alterations should design the temporary works.
Fire Protection
Steel loses structural capacity rapidly above 550°C. Building Regulations Approved Document B requires a minimum 30-minute fire resistance for elements of structure in most domestic situations, rising to 60 minutes for elements separating dwellings. In practice, beams installed above ceiling level and fully encased in plasterboard (12.5mm minimum each side of a cavity) typically achieve 30 minutes without additional treatment. Where the beam is exposed or in an open-plan area, intumescent paint (applied to a dry film thickness specified by the manufacturer, typically 1.5–3mm) or board encasement must be used.
Party Wall Act
If the beam bears on a wall that is shared with a neighbouring property — a party wall — the Party Wall etc. Act 1996 requires you to serve a Party Structure Notice at least two months before work begins. Your neighbour can consent or appoint a party wall surveyor. Failure to serve notice does not prevent the work but exposes you to a civil claim if the neighbour suffers damage.
Costs in 2026
| Item | Typical cost range |
|---|---|
| Structural engineer fee (residential beam calc) | £350–800 |
| Building Regulations application (Full Plans) | £200–400 |
| Steel supply (3m UB, common domestic section) | £150–600 |
| Acrow prop hire (2 weeks, 4–6 props) | £200–600 |
| Labour: wall removal, beam installation, making good | £800–2,500 |
| Padstone materials and setting | £100–300 |
| Plasterboard encasement / intumescent paint | £150–500 |
| Scaffolding (if needed for external works) | £400–1,200 |
| Typical all-in total (single wall removal) | £3,500–9,000 |
The wide range reflects span, location, access, and the scale of making-good required. A straightforward ground-floor internal wall removal with a 3m beam in a standard semi-detached house is typically £4,000–6,000 all-in when engaging a builder who handles the engineer engagement. High-end estimates apply where structural problems are discovered, where the beam is in a party wall situation requiring a surveyor, or where the floor finish above is expensive and must be perfectly reinstated.
Steel supply prices are influenced by global commodity markets and have fluctuated significantly in recent years; obtain quotes close to the time of ordering.
Post-Installation
Once the beam is in place and the temporary props removed, Building Control should inspect and sign off the structural element before it is enclosed. Keep the engineer’s calculations and the Building Regs completion certificate with the property deeds — they will be requested on any future sale or remortgage.
