Structural Alterations Eltham
Structural alterations, new openings, underpinning and floor structures in Eltham, designed by the engineer we appoint and inspected at every stage.
- Rated 4.9 from 31 reviews on MyBuilder
- London guide: from £1,500
- Free site survey, itemised quote
GS Renovation carries out structural alterations across Eltham, working on the 1930s and interwar houses that make up so much of SE9. Whether it is a new opening, replacement joists, a supported opening onto a rear extension or localised underpinning, our founder's 30+ years on the tools mean the work is engineered, propped and signed off properly.
In Eltham, a simple new opening starts from £1,500, and underpinning a single elevation typically costs £6,000 to £21,000 (indicative London ranges, MyBuilder and Checkatrade, 2026). GS Renovation Ltd, a building contractor based in Potters Bar, does the work in Eltham.
Price guide
| Work | Indicative London range |
|---|---|
| Simple new opening | from £1,500 |
| Underpinning, single elevation | £6,000 to £21,000 |
| Major structural works | from £15,000 |
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 Eltham address and an itemised quote.
- The engineer we appoint designs the work, and it is registered with the Royal Borough of Greenwich building control or an approved inspector. On a shared wall you serve the party wall notice as building owner; we supply the drawings.
- Props and any trial holes first, then the opening, joists or underpinning in the engineer's sequence.
- Building control inspects each stage before it is covered, then issues the completion certificate.
Structural alterations for interwar Eltham homes
The generous plots typical of Eltham mean owners often extend at the rear or reconfigure the ground floor, and both create structural work. Forming a supported opening between the existing house and a new kitchen extension needs a correctly sized steel beam on padstones; replacing tired or undersized floor joists in a 1930s semi needs the new spans checked. We start with an engineer's design for every alteration.
Underpinning comes up on some Eltham properties where an extension foundation must tie into the original, or where seasonal movement in the local clay subsoil has affected a corner. It is carried out in short, controlled bays so the house is never undermined all at once. Whatever the alteration, we prop first, work in a safe sequence and keep the structure supported throughout.
Housing in Eltham
For Eltham the Council Tax list gives about 14,360 homes; by type 27% flats and 73% houses, by age 30% post-war, 52% interwar and 17% older than 1919. 35% of homes here are semi-detached; underpinning the shared wall of a semi in Eltham needs a party wall notice.
Underpinning and cellar work under Royal Greenwich rules in Eltham
Underpinning has a line of its own in the Royal Greenwich building control charges: mass concrete underpinning is charged as its own item under a building notice, not folded into an extension or an opening. On an Eltham house where the engineer finds that the corner of a bay, or an old rear addition, needs taking deeper, that is a separate item on the paperwork, and the bases are inspected before concrete goes in. Plan the sequence of bays so that one visit can see several open excavations, instead of the whole programme stopping for a visit to each one.
Lowering a floor or turning a cellar into a room is where an Eltham owner meets the borough's basement rules. Royal Greenwich requires a Basement Impact Assessment for developments adjoining homes with new or enlarged basements, including cellar conversions into habitable accommodation, and a semi or a terrace always adjoins a home. The Structural Method Statement behind that assessment must be signed off by a Chartered Civil Engineer or Chartered Structural Engineer. Where the scheme needs planning permission, all of that is prepared before the application goes in, so a cellar scheme in Eltham starts with engineering and surveys well ahead of any builder on site.
Engineered and certified across the Royal Borough
Every structural alteration we make in SE9 is designed to engineer's calculations and inspected by building control under the Building Regulations. That covers new openings, beam and padstone details, joist replacements and any underpinning, with the Royal Borough of Greenwich or a registered building control approver checking the critical stages before the work is closed up and finally certified.
Where an alteration touches the party wall shared with an attached Eltham neighbour, for instance cutting a beam bearing into it or working near the shared foundation, the Party Wall Act applies and you serve notice before starting (or your surveyor does); we give you the drawings it needs. We coordinate the engineer, the propping and the building control inspections so you deal with one team from first drawing to final sign-off.
- Reinstatement, plastering and finishing after structural works
- Lintel replacement and repair over failed openings
- Temporary works, propping and needling
VOA Council Tax stock of properties, March 2025, for all 5 statistical areas in Eltham. Counts rounded by the VOA.
Trusted Structural Alterations in Eltham
For structural alterations in Eltham, homeowners rely on GS Renovation to keep everything under one roof: engineer-designed openings and underpinning, work programmed around any party wall notice you serve, building control inspections managed and safe staged working that never leaves the house unsupported. Clean, considerate work in occupied SE9 homes and a signed-off result, drawing on our founder's 30+ years on the tools.
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…
Built a new extension at rear of property. Laid foundations, drainage, raised floor, new roof and completed all fixtures and interior decoration…
Giorgio is an excellent and intelligent workman, and with very reasonable prices! He installed a kitchen extractor fan in a complicated situation…
FAQ
Frequently Asked Questions about Structural Alterations Eltham
Is a cheap structural alterations quote in Eltham worth taking?
Be careful with a cheap structural alterations quote in Eltham, particularly if nobody has visited. Pricing a 1930s suburban home unseen is how a low figure becomes a high one halfway through, because the load path through the Eltham building decides where support lands. GS Renovation surveys, itemises within £1,500 to £21,000 or more, from a simple opening to underpinning one elevation (indicative) and holds the total. A second opinion on the SE9 quotation costs nothing.
Is underpinning always needed when extending an Eltham house?
Not usually. Many Eltham extensions sit on standard trench-fill foundations designed for the local ground. Underpinning is only specified where an engineer finds existing foundations too shallow, where a new foundation must tie into an old one, or where movement in the clay subsoil has affected a wall. We only underpin when the structural design calls for it, in controlled bays.
Does widening a rear window into doors on an Eltham house need building control?
Yes. Cutting a wider hole in an outside wall means a new lintel or beam, which the engineer sizes and the inspector checks. On a 1930s cavity wall the inner and outer skins each need carrying, with a cavity tray over the head so rain cannot track into the new frame. A bearing in the party wall of a semi also brings in the Party Wall Act.
Is taking out an upstairs wall in an Eltham semi simpler than one downstairs?
Not necessarily. First-floor partitions in a 1930s house are often timber stud, but some carry ceiling joists, some have struts from the roof purlins bearing on them, and a few stand directly over the ground-floor spine. The loft tells you which. If the wall is holding roof load, the engineer designs a beam or a new strutting arrangement, and building control inspects it exactly as it would downstairs.
Can the Arts and Crafts cottages near Well Hall Pleasaunce in Eltham be altered structurally?
Yes, but with more checking than a standard semi. They were built quickly during the First World War, their construction varies from block to block, and many lie within a conservation area, which affects anything visible outside. The wall behind the roughcast render is opened and inspected before an engineer designs any support. If a particular cottage is listed, internal structural work also needs listed building consent.
What does an engineer need to see before designing an alteration in an Eltham home?
The whole load path, traced from the roof down. That means the purlin struts in the loft, the direction of the first-floor joists, what the wall below is built of and the condition of the brickwork where a padstone will sit. Where the local clay subsoil is a factor, the engineer may also ask for a trial hole beside an existing foundation before committing to an opening near an extension.
Could a two-level basement be dug under an Eltham semi?
Not with the borough's support. Royal Greenwich's Urban Design Guide says only single-storey basement extensions will be supported, citing their environmental impact and increased flood risk. A single level under part of the house is the scheme to design around. If it goes to a planning application it still needs the Basement Impact Assessment where the house adjoins another home, so the depth question and the neighbour question are answered in the same early engineering work.
Does the flood zone matter for a cellar conversion in Eltham?
It can decide whether one is allowed at all. Royal Greenwich will not permit basements in flood zone 3, and will not normally permit them in flood zone 2 unless no habitable rooms are proposed. Check the flood map for the address before anything is drawn. In flood zone 2, a cellar kept for storage or a boiler and cylinder is a different proposition from a bedroom or a family room below ground.
Does knocking down an old garage or outbuilding in an Eltham conservation area need permission?
It can. In Royal Greenwich conservation areas, planning permission is always needed for total or large demolition of a building measuring more than 115 cubic metres. Eltham Green Conservation Area was designated in 1975 and Eltham Palace Conservation Area in 1971. At an address in either, measure a detached garage or workshop before it comes down to make room for an extension. A rear wing joined to the house is part of a larger building, so ask the planning team in writing how they treat its removal.
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