RSJ and Steel Beam Installation New Barnet
Steel beam and RSJ installation in New Barnet, designed by the engineer we appoint and signed off by building control.
- Rated 4.9 from 31 reviews on MyBuilder
- London guide: £1,500 to £4,000
- Free site survey, itemised quote
GS Renovation installs steel beams throughout New Barnet, in its interwar semis, post-war houses and flats, and in the Victorian terraces where there is no side access and every beam has to come in through the front door. The steel is sized by a structural engineer we appoint, bears on padstones in sound masonry, and is inspected by Barnet Council building control before anything is closed up.
In New Barnet, 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 London ranges, MyBuilder and Checkatrade, 2026). GS Renovation Ltd, a building contractor based in Potters Bar, does the work in New Barnet.
Price guide
| Work | Indicative London range |
|---|---|
| Steel beam, one opening: supply, install, sign-off | £1,500 to £4,000 |
| Full knock-through with engineer and making good | £2,500 to £6,500+ |
Indicative London ranges (MyBuilder and Checkatrade, 2026), not a quotation. Prices checked September 2026. Full breakdown: RSJ & Load-Bearing Walls.
How the job runs
- Free site survey at your New Barnet address and an itemised quote.
- The engineer we appoint sizes the beam, and the work is registered with Barnet Council building control or an approved inspector. On a shared wall you serve the party wall notice as building owner; we supply the drawings.
- Props go in, the opening is cut and the beam is set on padstones, packed tight above.
- Building control inspects the steel before it is covered. We make good, and the completion certificate follows.
Getting steel into a mid terrace in EN4
On a detached house you carry the beam down the side and in through the back. A mid terrace in New Barnet has no side, so the beam comes through the front door, round the newel post at the bottom of the stairs and into the room, or in through a sash opening with the sashes taken out. That constraint shapes the design. A five metre 203 by 133 universal beam runs at roughly 25 kilos a metre, so it is a 125 kilo lift, and the turn at the foot of a terrace staircase decides whether it fits.
Where a single section will not physically get in, the engineer has options and they are not all equal. Two lighter beams bolted side by side can be carried in separately and made up in the room. A flitch of steel plate sandwiched between timber is another route where the load is modest. A spliced beam is possible but the splice detail has to be designed, not improvised on site. We raise the access question at survey, before a section is specified that nobody can get past the front door.
Housing in New Barnet
The Council Tax list puts the New Barnet and Hadley Wood statistical areas at about 10,670 homes, 50% flats against 50% houses; 17% went up before 1919, 32% between the wars and 52% after 1945. Since many homes here are flats, a beam in a leasehold flat in New Barnet needs the freeholder's licence first.
Bearing a beam on post-war cavity walls in New Barnet
In New Barnet 52% of homes were built after 1945, so the wall a new beam lands on is more often a cavity wall than solid Victorian brick. That changes the bearing. The padstone normally sits on the inner leaf alone, and in a later house that leaf can be lightweight block, which can crush under a point load that brick would carry. The structural engineer we appoint needs to know which block is there before choosing the padstone length, so we open a small inspection hole at each bearing during the survey rather than guessing from the age of the house.
Where the beam forms a wider opening in an external wall, the cavity brings its own details. A cavity tray and weep vents go over the new opening so water running down the inside of the outer leaf is sent outside, not onto the steel or the new door head. The cavity is closed at the reveals with an insulated closer. Any mortar that drops down the cavity during the cut is cleared out, because a mortar bridge at the base carries damp straight across to the inside wall of a New Barnet front room.
Bearings, notices and inspection in New Barnet
The bearing is where beams go wrong. In an EN4 terrace the pocket is cut into a party wall built of soft yellow stock laid in lime mortar, which will not take a point load on its own, so the engineer specifies a padstone and a bearing length and both get checked before the steel goes in. If the brickwork behind the pocket is poor we cut back and rebuild in engineering brick rather than pack the padstone up. Propping stays in until the packing is tight and the props come out in a stated order.
Cutting a pocket into a party wall is notifiable under the Party Wall etc. Act 1996. In a mid terrace both ends may land in a shared wall, which means two adjoining owners, and around New Barnet station some of those neighbours are flats with a freeholder and a managing agent behind them. You serve the notices as building owner; we prepare the structural information behind them and work to the agreed method. Barnet Council building control inspects the beam and bearings before plaster goes anywhere near them.
- Load-bearing wall removal and knock-throughs
- Beam boxing, fire protection and plasterboard encasement
- Steel columns, base plates and bolted connections
VOA Council Tax stock of properties, March 2025, for the New Barnet and Hadley Wood statistical areas, which also take in East Barnet and Hadley Wood. Counts rounded by the VOA.
Trusted RSJ and Steel Beam Installation in New Barnet
New Barnet owners choose GS Renovation for steel because we treat access and bearing as design problems rather than site surprises. The engineer is appointed by us, the beam is sized and detailed before we quote, the party wall information is ready for your notices, and Barnet building control inspects at the right stage. Founder led, fully insured, with 30+ years of hands-on structural experience.
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FAQ
Frequently Asked Questions about RSJ and Steel Beam Installation New Barnet
How do you price RSJ and steel beam installation in New Barnet?
The method for pricing RSJ and steel beam installation in New Barnet is deliberately dull: measure, scope, itemise, then compare with £1,500 to £4,000 for one beam opening (indicative). Nothing is quoted over the phone, because a blind figure changes later. GS Renovation allows for the post-war construction at EN5 and prices the engineer's calculations and a Barnet Council building control inspection of the bearings as its own line.
How do you get a steel beam into a mid terrace with no side access?
Through the front door, or through a window opening with the sashes removed, and the turn at the foot of the stairs is usually the limiting point. We measure that route at survey and tell the engineer, because it affects what can be specified. If a single section will not go, the alternatives are two lighter beams bolted together in the room, a designed splice, or a flitch beam of steel plate between timbers. All of them are the engineer's call. What we never do is force a section round a corner and damage the staircase.
What does the engineer check before sizing a beam in a New Barnet house?
Everything that bears down on the wall and everything beneath it. They look in the loft for struts, lift boards to see which way the joists run, check for walls or a tank above, and ask what the beam ends will sit on. Only then are the calculations done. Those calculations go to building control, and they set the section size, padstone and bearing length.
When does building control inspect an RSJ in New Barnet?
At least once while everything is still visible. The calculations are approved first, then the inspector visits when the beam is seated on its padstones, with the packing tight and before any boarding or plaster. Barnet Council or a registered building control approver issues a completion certificate at the end. Closing the beam in before that visit usually means opening it up again.
Does a steel beam in my New Barnet flat need fire protection?
Yes. Steel weakens quickly in fire, and in a building of flats the beam is often supporting part of the floor between homes, so it has to be encased to the fire resistance building control sets. That usually means fire-rated board. The lease normally requires the freeholder's written consent before the structural work begins, so that approval is sought first. With about half of New Barnet's homes being flats, this is common.
What goes between the top of the beam and the wall above in a New Barnet house?
Packing, and it matters. After the steel is lifted onto its padstones, the gap between its top flange and the brickwork above is filled tight with dry pack mortar or steel shims, so the load transfers without the wall settling onto it. Only once the packing has taken up do the props come out. Loose packing is how new cracks appear in the bedroom above a week later.
Where do the original drawings for a newer New Barnet house come from before steel is designed?
Start with the handover pack from the developer, then look up the original permission on Barnet Council's planning register for the approved drawings. Council building control records help only if the council, not a private inspector, checked the build. In New Barnet 11% of homes were built in 2000 or later, and for those the joist layout and lintel schedule may still exist on paper. Drawings do not replace opening up, but they tell the structural engineer we appoint where to look first.
Does a beam over new garden doors in New Barnet need planning permission?
On a house, usually not. The steel is a building control matter, and replacing a rear window with doors normally falls within householder rights, in a conservation area too. The exceptions are a flat, where a change to the outside generally needs permission, and an Article 4 direction covering doors or windows. Planning Data returns 16 conservation area results for Barnet, and each Barnet direction lists its own works, as the Glenhill Close Conservation Area one does for gates, fences and walls. Check your New Barnet address before the doors are ordered.
Can a steel beam go into a purpose-built post-war flat in New Barnet?
Sometimes, but the structure is the block's, not the flat's. Half of New Barnet's homes are flats, and in a post-war block an internal wall can be carrying concrete floors for every flat above. The structural engineer we appoint needs the block's structural form before any opening is sized, and the freeholder decides whether it may be touched at all. Where the wall carries the building, the honest answer can be a smaller opening or none.
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