RSJ Installation in Southampton: What's Involved
Updated: Oct 4
If you're planning to open up a wall in a Southampton home, whether that's knocking through between the kitchen and dining room in a Portswood terrace or creating open-plan living in a 1930s semi out towards Bitterne, the wall itself is rarely the hard part. The steel beam that replaces it, and everything that has to happen before and after it goes in, is where the real work sits. We install structural steel across Southampton and the wider Hampshire coast most months, and the process is more involved than people usually expect when they first call us.
A lot of what decides whether a job like this goes smoothly happens before anyone picks up a tool. Get the survey wrong, skip the calculations, or rush the paperwork, and you end up with a beam that's undersized, a floor that bounces, or a headache when you come to sell. Here's what actually happens on a typical RSJ job for us, what it costs right now, and what you can expect if you're thinking about doing this in your own home.
What Actually Happens When You Take Out a Load-Bearing Wall
Before we quote anything, we get a structural engineer out to look at the wall in person, not just at photos you've sent over. They work out what's actually bearing down on it (a chimney breast changes the loading completely), size the beam accordingly, and produce the drawings Building Control will want to see. We don't skip this step even on a wall that looks straightforward, because guessing at the loading is how you end up with cracked plaster, or worse, a structural problem a few years down the line.
On site, the wall stays exactly where it is until it's properly supported. We put Acrow props either side of the opening, resting on padstones or timber spreader plates so the load's carried down to something solid rather than a floorboard. Only once that's in place is the wall taken out, the new steel lifted into position, packed and pinned, and left to take the weight before the props come down. Most of a day goes on the propping and opening up alone before the beam even goes in, so it never happens as fast as people expect from watching it on TV.
What It Costs in Southampton Right Now
Every job is priced after a survey, because span, wall thickness and what's sitting above it all move the number. But to give you a realistic starting point for a typical single-beam opening in a Southampton semi or terrace, here's roughly what you're looking at with us:
Structural engineer's calculations and Building Control-ready drawings: £550–£650
Steel beam supply, Acrow props, padstones and fitting: £1,900–£2,600
Building Control application and inspection: £300–£600
Making good afterwards, plaster and prep for redecoration: usually £350–£450
All told, most straightforward single-beam jobs we quote around Southampton come out at £3,200–£4,800 all-in. A longer span, a second beam, or a wall that's also carrying a chimney will push that higher, and we'll walk you through exactly why before you commit to anything.
How Long It Takes and What to Expect On Site
Once the engineer's drawings are signed off, most single-beam jobs are in and made good within two to three days on site. Add the time for calculations and Building Control approval beforehand and you're usually looking at two to three weeks from first survey to finished opening. There'll be dust sheets down, some noise while the wall comes out, and a day or so where that part of the house is propped and off-limits, but it's a short, contained job rather than a full renovation.
Southampton's Housing Stock Has Its Own Quirks
We see a real mix of properties across the city. The Victorian and Edwardian terraces around Portswood and Shirley often have solid brick internal walls thicker than people expect, sometimes with a chimney breast bearing straight down onto the opening you want. The 1930s semis out towards Bitterne, Sholing and Woolston tend to be more straightforward, single-skin walls carrying joists rather than a full first floor above. And some of the post-war stock around Weston and Townhill Park has timber-frame or non-standard construction that needs a closer look before we can say for certain what's load-bearing at all. None of this is a problem, it just means the survey earns its keep more on some streets than others, and it's why we won't quote a number over the phone.
Why We Never Skip the Paperwork
We get asked fairly often whether Building Control sign-off is something you can skip on a small job. We don't skip it, on anything. A completion certificate is what proves the work was done properly if you ever come to sell, and mortgage lenders and solicitors will ask to see it before a sale can complete. Every RSJ we install in Southampton gets signed off, which is exactly what you want from whoever's doing this kind of structural work in your home.
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Thinking About Opening Up a Wall?
If you're weighing up knocking through in a Southampton property, get in touch and we'll arrange a book a site visit through completebuilds.co.uk before we put a number on anything. We'll talk you through exactly what your wall needs, calculations and costs included, before anything's locked in.
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