Structural Alterations Wimbledon
Structural alterations, new openings, underpinning and floor structures in Wimbledon, 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
From new door openings to replacement joists and underpinning, GS Renovation carries out structural alterations throughout Wimbledon's Victorian and Edwardian terraces. Working across SW19, backed by our founder's 30+ years on the tools, we understand how these bay-fronted homes with their rear closet wings and side returns are put together, and how to alter them without weakening the structure.
In Wimbledon, 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 Wimbledon.
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 Wimbledon address and an itemised quote.
- The engineer we appoint designs the work, and it is registered with Merton 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 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 tailored to Wimbledon homes
The rear closet wings and side returns typical of Wimbledon terraces throw up their own structural puzzles: forming a supported opening between a return and the main house, or replacing joists that have sagged or suffered decay over a century of use. Every alteration starts with an engineer assessing what is being carried, then specifying the steel, timber or masonry needed to take the load safely.
New openings for wider doorways or serving hatches are formed with a lintel or beam bearing onto padstones, propped while the masonry is cut and let in once the support is seated. Where original joists have failed, we replace them on new bearings and tie the floor back together, so the alteration is stronger than what it replaced rather than a patch that hides the problem.
Housing in Wimbledon
Count the homes in Wimbledon and you get about 25,760: 38% built since 1945, 10% between the wars and 52% before 1919, with flats at 51% and houses at 49%. Most homes here are flats, and structural repair to a block in Wimbledon usually falls to the freeholder under the lease, so it is agreed with them before anything is opened up.
Enlarging a Wimbledon cellar under Merton's basement policy
Merton Local Plan Policy D12.11 only permits basement and subterranean developments that do not cause harm to the built and natural environment and amenity. For an older Wimbledon house with a cellar, that policy is where a plan to lower the floor or dig out under the rest of the house begins. Merton's basement policy requires every basement application to include a Basement Impact Assessment, a Drainage Strategy and an outline Construction Method Statement, so ground investigation and drainage design are commissioned before the planning application, not after it.
Size is capped as well. Under Merton's basement policy, a basement added to an existing building must not extend beyond the original outer walls to more than 50% of the original dwelling's footprint. A dig-out under a Wimbledon garden therefore has a limit set by the house, not the plot. Structurally, deepening an existing cellar means underpinning its walls in sequence, and some of those walls may be shared with the neighbours, so party wall notice is needed. The building owner serves it once the engineer's scheme is ready and before any excavation is booked, covering digging near a neighbour's foundations as well as any shared wall.
Underpinning and consents in SW19
Some older Wimbledon terraces show settlement cracking, often on the clay soils around Wimbledon Common, and here underpinning may be the answer. We work to an engineer's scheme, excavating and casting in bays so the foundation is never undermined all at once, and building control inspects each stage before it is covered up.
Because many of these alterations affect the shared party wall with the neighbouring terrace, the Party Wall Act applies and you serve notice as building owner before work starts, with underpinning to a party wall specifically notifiable. Internally the work sits under building regulations and Merton's building control, not planning, although a listed house also needs listed building consent. We coordinate the engineer and the inspections so the whole alteration is properly signed off.
- Underpinning and foundation strengthening in sequenced bays
- Steel goalpost and portal frames to the engineer's design
- Load paths carried down to foundations on new piers and pads
VOA Council Tax stock of properties, March 2025, for all 7 statistical areas in Wimbledon. Counts rounded by the VOA.
Why Choose GS Renovation in Wimbledon
GS Renovation gives Wimbledon homeowners a single team for the full alteration: the engineer's design, underpinning or new openings built in safe stages, and building control sign-off with Merton. Our founder's 30+ years on the tools means we anticipate the quirks of closet wings and side returns before they become problems on site.
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…
George was brilliant. Lovely bloke, very reasonably priced and a perfectionist to boot. He completed our small kitchen renovation with care and great…
FAQ
Frequently Asked Questions about Structural Alterations Wimbledon
Does the cost of structural alterations rise in a late Victorian or Edwardian Wimbledon property?
In a late Victorian or Edwardian Wimbledon home the unknowns behind plaster are what move a structural alterations figure within £1,500 to £21,000 or more, from a simple opening to underpinning one elevation (indicative), which is why the SW19 survey matters more there. GS Renovation prices the visible work, names the risks, and agrees anything additional in writing. The approvals do not change with age: an engineer's design approved before the work starts applies either way.
My Wimbledon terrace has settlement cracks near the bay: is underpinning always needed?
Not always. Cracking can come from old lintels, tree roots or minor movement that has stopped. We arrange a structural engineer to diagnose the cause first. If underpinning is warranted, it is done to their scheme in sequenced bays and inspected by building control. Where it touches the shared party wall, you serve notice on your neighbour beforehand, as building owner.
Can I remove the purlin struts in my Wimbledon loft?
Not without replacing what they do. In the larger SW19 villas the struts carry the purlins, which support the rafters partway along their length, and they often stand on an internal wall below. Taking them out for a loft room means the engineer designs a new support, usually steel purlins or a beam spanning between walls that can take the load. Building control inspects it as structural work.
Does a small new doorway in my Wimbledon house need building control?
Yes, if the wall is load-bearing, whatever the size of the hole. Forming an opening in a structural wall is Building Regulations work under Part A, so it is notified to Merton Council building control, with an engineer's lintel specification. On a solid Victorian wall the lintel carries the full thickness, and props or needles hold the brickwork while it is cut. The inspector sees the bearing before plaster.
My Wimbledon house is listed. What changes for structural work?
Internal structural alterations to a listed building need listed building consent, which normally means an application before any building control approval is useful. The consent process looks closely at which historic fabric is removed, so the engineer's scheme may need to keep more of the original than a standard design would. Allow for that in the programme, and do not open anything up until consent is granted.
Can I make a wide opening in the rear wall of my Wimbledon terrace?
Usually, and it is a common request here. On a solid wall the beam carries the full thickness of brickwork above, often with a flat roof or bathroom window over it, so the engineer checks what sits above before sizing. The wall is needled and propped, the opening cut, and padstones set in sound masonry. Merton building control inspects the bearings before anything is covered.
What reports does Merton ask for before a Wimbledon cellar is dug deeper?
Merton's basement policy requires every basement application to include a Basement Impact Assessment, a Drainage Strategy and an outline Construction Method Statement. The assessment looks at ground, water and neighbouring structures, the drainage strategy deals with where water goes, and the method statement shows how the dig is propped and sequenced. Commission them together, because each informs the others.
How far can a basement extend beyond the walls of a Wimbledon house?
Under Merton's basement policy, a basement added to an existing building must not extend beyond the original outer walls to more than 50% of the original dwelling's footprint. The footprint is the original dwelling's, before later alterations, so an existing rear extension does not enlarge the allowance. Establish that footprint from old plans or a measured survey before the design goes further.
Does converting an office in Wimbledon town centre to flats need planning permission?
Yes, in the areas Merton's Article 4 direction covers. That direction requires planning permission to convert offices to homes in areas including Wimbledon town centre and Garth Road industrial estate, Lower Morden. The structural works, new stairs and fire separation between the flats then follow the approved layout, so the engineer designs to the permitted scheme rather than ahead of it.
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