RSJ and Steel Beam Installation London

RSJ installation in London means putting a steel beam where brick used to do the work, so a wall, a chimney breast or a failed lintel can come out without the floors above noticing. The wall you want gone is almost always carrying something. Most London beams are universal beams rather than true rolled steel joists, but the trade still says RSJ, so this page does too. Below you will find how the job runs on site, who designs it, which consents you need, what it costs in London and what we see go wrong on other people's openings. GS Renovation installs steel beams across London and the surrounding counties, building to a design from the structural engineer we appoint and to building control inspection. Read it before you collect any quotes for a knock through or a wider doorway.

Across London, a steel beam for one opening typically costs £1,500 to £4,000 fitted and signed off, or £2,500 to £6,500 or more for a full knock-through with the engineer's fee and making good (indicative ranges, MyBuilder and Checkatrade, 2026). GS Renovation Ltd, a building contractor based in Potters Bar, does the work in London.

Which London homes need RSJ installation?

RSJ installation in London comes up in four kinds of building, and each changes how the beam is fitted. In a Victorian terrace the walls are solid nine inch brick laid in lime mortar, with a spine wall between the two reception rooms and a rear closet wing carrying its own roof. Those walls carry floor joists and often a chimney stack, so the beam needs proper bearings at each end. Lime mortar is soft, so the engineer specifies padstones rather than letting the beam sit straight on the brick. The interwar semi has cavity external walls with a single skin inner leaf, so a beam bearing on the inner leaf usually needs a spreader plate or a built up pier to take the point load.

Flats and conversions bring their own problems. In a mansion block the floor between you and the flat below is a party structure, and the freeholder will want a licence to alter before any steel goes in. The beam is often designed to sit within the floor zone rather than below it. In a house converted decades ago, the previous work may never have had calculations. We regularly find timber lintels doing the job of a steel, beams bearing on a single brick, and openings widened without anyone checking what the wall above carried. Then the new beam has to correct the old work as well as carry the new opening, and the engineer's survey is where that gets picked up.

How does steel beam installation run on site?

A steel beam installation runs in a fixed order, because for part of it the floor above is standing on temporary props. After the survey the structural engineer we appoint traces the load path, sizes the beam and details the bearings, padstones and any restraint. The steel is then fabricated to that drawing. On the first site day we sheet the room, lift boards to confirm joist direction, and trace services in the wall. Propping goes in next: needles through the wall above the opening line, carried on acrow props standing on sole plates, or strongboys where there is only one side to work from. Only once the load is fully on the props does any brick come out of the wall.

The opening is cut, the bearings are formed and the padstones bedded and left to cure. The beam is lifted onto the padstones, packed tight to the masonry above with dry pack mortar, and bolted where the design calls for it. Building control inspects with the steel and its bearings exposed, and again at completion. The props stay in until the packing has taken up, because striking them early lets the wall above settle onto the beam and crack. Then comes fire protection to the steel, either fire rated boarding or an intumescent coating, followed by plastering and decoration. The engineer designs, we build to that design, and building control checks it. None of those three roles should be the same person.

Consents for RSJ installation in London

Installing a steel beam in London needs building regulations approval every time, and planning permission almost never. The work is controlled under Part A of the Building Regulations for structure and Part B for fire, with Part P if circuits in the wall have to be moved. You can go the full plans route, where the engineer's design is checked before work starts, or a building notice, where the inspector approves the work as it is built. We prefer full plans, because nothing is then argued about with your ceiling already propped. An ordinary internal opening needs no planning permission. If the house is listed, listed building consent covers internal structural work like this, and working without it is a criminal offence. The application routes and the inspections are explained on our building control page.

If the beam bears into a wall you share with a neighbour, the Party Wall etc. Act 1996 applies. You, as the building owner, serve a party structure notice at least two months before the work, and your neighbour can consent or appoint a surveyor. If they dissent, an award is drawn up before the work begins, and we build to it. We do not serve notices and we are not surveyors, but we give you the engineer's drawings the notice relies on. Speak to your neighbour early and in person, and see our party wall page for the notice periods. In a mansion flat, ask your freeholder or managing agent for a licence to alter before you engage anyone. If the wall is a stud partition running parallel to the joists, you may not need a beam, or us, at all.

What does RSJ installation cost in London?

A steel beam on one straightforward opening, supplied, installed and signed off, costs £1,500 to £4,000 in London. A full knock through, including taking the wall down, the engineer's fee and making good, runs £2,500 to £6,500 or more. Those are indicative London ranges, MyBuilder and Checkatrade, 2026, not a quotation, and a firm price follows a survey. The steel itself is rarely the biggest line. Labour, propping, the engineer, building control and the plastering afterwards are where most of the money goes, so a cheap quote is usually a quote that has left one of those out. Both figures assume a single beam. Ask what is excluded before you compare two quotes, and check that both assume the same access.

What moves the price is mostly what the wall is doing and where it is. A wall carrying a chimney stack needs a heavier section and a more involved propping plan. A beam that has to be spliced to get through the front door, or landed on a goalpost frame where two walls meet at a corner, costs more than one lifted straight onto padstones. A soil stack or the consumer unit in the wall means another trade before demolition. A flush beam, set within the floor zone with the joists on hangers so the ceiling runs level, costs more than a downstand boxed in below it. We recommend the downstand unless the bulkhead would land in the middle of a kitchen diner.

Living at home during steel beam installation in London

You can usually stay in the house while a beam goes in, but the room it goes into is out of use for the duration. In a London terrace the beam comes in through the front door and along the hall, so long beams are fabricated in two sections and spliced on site with bolted plates the engineer designs. We measure the hall on the survey, not on delivery day. Steel and skip deliveries need kerb space, and on a permit street that means arranging a suspension with the council in advance. Dust from cutting brick travels, so we sheet doorways and seal the room, but a kitchen that shares a wall with the opening should be emptied of anything you value.

Flats add a layer of rules. Most blocks limit working hours to weekday daytimes, want the managing agent told before deliveries and expect lifts and common parts protected. Weekend working is rarely allowed. A licence to alter will often set those conditions in writing, and we work to them. Neighbours in a terrace will hear the cutting and feel the drilling for the bearings. Tell them the dates, especially if a party wall award is in place, because the award may fix hours too. We keep one named point of contact on the job so that you, your neighbour and the managing agent all ring the same person, and so that the answer you get is the same one every time.

What goes wrong with RSJs, and choosing a London contractor

Most failed steel we are asked to look at in London went wrong before the beam was lifted, in the design or the bearings. A beam sized by eye may hold the floor and still deflect enough to crack the wall above and jam the bedroom doors. A beam landed on a single brick, with no padstone, crushes the masonry and shows as stepped cracking within months. On interwar cavity walls we see beams bearing on the inner leaf alone with nothing to spread the load. We see props struck the same afternoon, before the dry pack has cured, and steel boarded over before the inspector came, which means opening it back up. And we still find bare steel with no fire protection.

Choosing a contractor for RSJ installation comes down to a few plain questions. Ask who is designing the beam, and expect the answer to be a named structural engineer, never the builder. Ask for the propping method, and expect needles or strongboys on sole plates, not props wedged under the joists. Ask whether building control is notified on every job, and whether you will get the completion certificate. Ask who you will speak to when something changes, and whether the trades on site are their own people. Ask for a written quotation after a survey rather than a figure over the phone. A contractor who is comfortable with those questions is usually one who has done the work properly before.

• Load-bearing wall removal and knock-throughs
• RSJ and structural steel beam installation
• Party wall process explained, and the beam built to the award

Useful next reading for an RSJ and steel beam installation project in London: home renovation in London, building control sign-off for a steel beam, party walls and steel beams and Cracks in Walls: When to Worry.

Why London Homeowners Choose GS Renovation

You would choose GS Renovation for RSJ installation in London because the structure is the whole job for us. Abdelaaziz Saaid, our founder and director, has over 30 years of hands on experience with steel in London houses, and he is who you speak to. We appoint the structural engineer, build to the design, coordinate building control on every notifiable job and use our own trades rather than a subcontractor chain. We are fully insured, quote in writing after a survey with no obligation, and are rated 4.9 from 31 reviews on MyBuilder.

• High-density concrete padstones bedded at every bearing
• Temporary propping in place before anything is cut
• Honest updates if a date or a detail has to move

Checked by Abdelaaziz Saaid, founder and director of GS Renovation Ltd (Companies House no. 14611254). Structural design is by the consulting engineer appointed to your project.