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Steel Beams for Removing a Load-Bearing Wall
Take out a wall that is holding something up and the load has to go somewhere else. The beam is what carries it across the new opening.
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First, is it actually load-bearing?
Not every internal wall is. The usual signs that one is doing structural work are that it runs at right angles to the floor joists above, that it sits above another wall on the floor below, that it continues through more than one storey, or that it is masonry rather than stud. None of those is conclusive on its own, and the only reliable answer comes from someone opening up and looking.
It matters because the question is not really whether the wall is load-bearing, but what it is carrying. A wall taking only the ceiling above is a very different problem from one carrying a floor, another wall, and a roof.
What governs the beam size
Three things: the clear span of the opening, the load coming down onto the beam, and how much depth the beam is allowed. Widening an opening from three metres to four does not increase the demand by a third — bending moment rises with the square of the span, so it rises considerably faster than the opening does. That is why a modest increase in opening width can mean a noticeably heavier section.
Deflection is usually what governs domestic openings rather than raw strength. A beam can be strong enough and still move enough to crack the plaster above it, so the design is often working to a deflection limit. That is also why an engineer may specify a heavier section than the span alone would appear to need.
Bearings, padstones and propping
The beam has to land on something that can take the load. That is normally a padstone — a concrete block that spreads the end reaction into the masonry below. Padstone size comes from the calculations and is not a detail to improvise; too small and the load concentrates and crushes the brickwork underneath.
The other half of the job is temporary support. The structure above has to be held while the wall comes out and the beam goes in, and that propping needs planning before anyone starts. The beam’s cut length has to include the bearing at each end, which is why ordering to the clear opening width is such a common and expensive mistake.
Typical sizes for this job
Sections commonly specified for internal openings in domestic work, from a small knock-through to a full-width structural wall removal.
| Size | Weight | Indicative Span | Typically Used For |
|---|---|---|---|
| 127 x 76 x 13 | 13 kg/m | 2–2.5m | Small openings with light load above |
| 152 x 89 x 16 | 16 kg/m | 2.5–3.2m | Standard terrace knock-through between reception rooms |
| 178 x 102 x 19 | 19 kg/m | 3–3.5m | Wider openings in a semi-detached house |
| 203 x 133 x 25 | 25 kg/m | 3.8–4.5m | Larger knock-throughs, wall plus floor above |
| 254 x 146 x 31 | 31 kg/m | 4.5–5.2m | Full-width removal on a mid-size house |
| 254 x 146 x 37 | 37 kg/m | 4.8–5.5m | Where the beam picks up an upper floor as well |
What else the steel will need
Most beams need more than cutting to length before they reach site. All of it is arranged on the same order:
- Cut to size
- Painting, priming and intumescent coating
- Welded cleats, end plates and connections
- All processing and fabrication services
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Common questions
How do I know if a wall is load-bearing?
Common signs are running at right angles to the joists above, sitting above another wall below, continuing through more than one storey, and being masonry rather than stud. None is conclusive — get a structural engineer to confirm before planning the job.
What size beam do I need for a 4 metre opening?
It depends on what the beam is carrying, not just the span. A 4 metre opening under a light load and a 4 metre opening carrying a floor and a wall above will give very different answers. The calculations decide it.
Do I need padstones?
Almost always. The beam concentrates its load at each end, and a padstone spreads that into the masonry below. The size comes from the calculations.
Does the beam need to be longer than the opening?
Yes. The cut length is the clear span plus the bearing at each end, as specified by your engineer. Ordering the clear opening width is a common and costly error.
Ready for a price?
Send your drawings or a cutting list and we’ll come back with quantities and a price. Large and small orders both welcome.
We supply structural steel across London, the South and the Midlands, delivered direct to site. Information on this page is general guidance; the specification for your project must come from your structural engineer.
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