RSJ and Steel Beam Installation Lewisham
Steel beam and RSJ installation in Lewisham, 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 RSJs and steel beams across Lewisham, from the bay-fronted Victorian terraces of Forest Hill in SE23 to the Edwardian family homes of Lee and Hither Green in SE12 and SE13. We remove load-bearing walls safely, opening up the tight, cellular layouts typical of these period terraces while keeping the house sound.
In Lewisham, 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 Lewisham.
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 Lewisham address and an itemised quote.
- The engineer we appoint sizes the beam, and the work is registered with Lewisham 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.
Removing load-bearing walls in Lewisham terraces
The classic Lewisham job takes out the wall between the front and rear reception rooms, or the wall into the rear closet wing, to make a single open living space. Because these Victorian and Edwardian terraces carry floor and roof loads through those internal walls, a structural engineer sizes the steel beam first. We then set the RSJ onto concrete padstones at each end so the load spreads safely into the remaining brickwork.
Safe sequencing matters on an occupied street in SE4 or SE6. We install temporary props, Acrows and strongboys, to hold the structure above, then carry out staged demolition rather than pulling the wall down in one go. Once the beam is in and bearing correctly, we remove the props, fireproof and box in the steel, and make good. Lewisham Council building control inspects the work and signs it off, giving you the completion certificate you need.
Housing in Lewisham
Lewisham has about 133,910 homes on the Council Tax list: 34% pre-1919, 18% interwar and 45% post-war, with flats making up 60% and houses 40%. A beam in a leasehold flat in Lewisham needs the freeholder's licence for alterations, since the lease usually keeps the structure with the freeholder, which matters here because most homes are flats.
Steel over a widened rear opening in a Lewisham house
Lewisham's building control fees chart gives structural support for new glazing, such as a new door, a line of its own, separate from the line for removal of an internal wall. That distinction matters in Lewisham because a beam job can be two jobs in one: a steel over a widened rear opening for doors to the garden, and a second steel where the back reception wall comes out. Describe both when the application goes in. An inspector who arrives expecting one beam and finds two has to see the second set of calculations before the props come out, and the doors and the boarding wait until they have.
The rear wall of a house built before 1919 (34% of Lewisham homes) is normally solid brick with no cavity, often laid in a soft lime mortar, and the old opening may be spanned by a timber lintel rather than anything designed. Steel over a wider opening in that wall has to carry the full thickness of brickwork, so the structural engineer we appoint may specify two sections bolted side by side or a beam with a plate under its bottom flange. We cut the padstone pockets by hand and pack the steel tight to the brick above before any prop is struck, because any gap left over the steel closes up as the brickwork settles, and that shows as cracks.
Party wall notices for Lewisham terraces
Terraces in Brockley, New Cross and Catford share a party wall with the house next door, and the chimney breasts and stacks are often built into that shared wall. When your steel beam bears near or into it, the Party Wall etc. Act 1996 usually applies. That means you, as building owner, serve formal notice on your neighbour before work starts, typically two months ahead, so the process is agreed and everyone is protected.
We are used to coordinating this across Lewisham's tightly packed streets. Where a chimney breast is removed on a lower floor, the stack above must be properly supported on a steel beam, or on gallows brackets only where the engineer and building control accept them, again to the engineer's design. We can recommend a party wall surveyor, prepare the technical drawings your neighbour's side will want to see, and time the notice period so it does not hold up the rest of your build.
- Bearing checks into party walls and shared masonry
- Beam boxing, fire protection and plasterboard encasement
- Making good, plastering and finishing around the new steel
VOA Council Tax stock of properties, March 2025, for all 37 statistical areas in Lewisham. Counts rounded by the VOA.
Why Lewisham Homeowners Choose GS Renovation
Lewisham homeowners choose GS Renovation because we handle the whole structural job under one roof, from the engineer's calculations to the propping, the beam and building control sign-off. With our founder's 30+ years on the tools, we work cleanly in occupied homes and stand behind every beam we install.
Reviewed jobs near Lewisham
1 MyBuilder review from Crofton Park, with each customer's own job title:
- Replace small section of wooden worktop, sink, tap and gas hob, Crofton Park, 17 Apr 2024 (5 out of 5)
Read all 31 on our reviews page.
We loved working with George and Ibrahim and would highly recommend them. They have done splendid job on our new kitchen refurb which including new…
George was brilliant. Lovely bloke, very reasonably priced and a perfectionist to boot. He completed our small kitchen renovation with care and great…
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FAQ
Frequently Asked Questions about RSJ and Steel Beam Installation Lewisham
How does your RSJ and steel beam installation price in Lewisham compare with a national firm's?
A GS Renovation price for RSJ and steel beam installation in Lewisham compares well with a national firm's because there is no head office to fund, and both should sit within £1,500 to £4,000 for one beam opening (indicative). GS Renovation is the contractor doing the work at SE13, not a broker adding a margin. Compare the scope, including building regulations approval of the engineer's beam design, not just the total.
Does the mixture of housing in Lewisham change how steel is specified?
It changes it substantially. Lewisham contains Victorian terraces, interwar semis, post war houses and blocks of flats, and the floor construction and wall build up differ across all of them. A beam bearing into solid brickwork is a different detail from one bearing into a cavity wall or connecting to a concrete frame. The engineer designs from what the building actually is.
How does a concrete floor affect steelwork in a Lewisham property?
It changes both the propping and the connection. Where your Lewisham property has concrete floors, the load arriving at a new beam is greater than from a timber floor and the temporary support has to suit. Fixing into concrete also differs from building into brickwork, and the engineer specifies the connection detail. None of it is unusual, but none of it is the same as a timber floored terrace.
Can a beam be installed in a Lewisham flat above another home?
Yes, with the design accounting for the floor as shared structure. In your Lewisham flat the floor being cut for a bearing is also the ceiling of the home below, and it provides fire and sound separation for both. The engineer designs the bearing and the trimming accordingly, the separation is reinstated, and the freeholder's licence is obtained alongside building control approval.
What hours can structural work be carried out in a Lewisham flat?
Whatever the lease, the managing agent and the council's rules on construction noise allow, and those are established first. Noisy work in a Lewisham building affects every other home in it, so percussive activity is concentrated into agreed periods rather than spread across the day. Neighbours are told in advance what will happen and roughly when. That costs nothing and prevents most complaints.
What is agreed about waste removal at a Lewisham property?
Who provides it, where it stands and how often it goes. On a Lewisham job a skip on the public highway needs a licence from the highway authority with lighting and markings, while a driveway or forecourt avoids that entirely. Where neither is available, bagged waste on scheduled collections is used instead. The arrangement is settled before the start date rather than on the first morning.
Does Lewisham building control approval mean the neighbour has agreed to the beam?
No. Lewisham Building Control says the Party Wall Act is a civil matter and it is not involved in the Act's administration. An approved beam design therefore says nothing about next door. Where a steel in a Lewisham terrace bears into the party wall, the building owner serves notice, and we order the steel only once written consent or an award is in place, since Lewisham Building Control will not chase it. A beam delivered before the neighbour has answered just sits in the front garden.
How quickly can steelwork start in Lewisham once a building notice goes in?
Lewisham says that once a building notice is submitted, work can commence within 48 hours. That speed moves the design risk onto site, because no plans are checked in advance. The calculations and drawings from the structural engineer we appoint must be ready for the inspector's first visit. For a single beam in a Lewisham house this route can be sensible, but we lodge the notice only after the calculations are finished, since a notice sent before the design is fixed gains nothing.
Does swapping a sagging timber lintel for steel in a Lewisham house need approval?
Yes. Beams sit on Lewisham's list of structural alterations that need building control approval, and that list covers removal or partial removal, not only new work. A rotten timber lintel or bressummer over a bay or a back door is a beam carrying brickwork, so replacing it with steel is controlled work. In Lewisham period houses these can turn up when render or plaster comes off. The structural engineer we appoint sizes the replacement, and the inspector sees it before it is covered.
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