Structural Alterations Wandsworth
Structural alterations, new openings, underpinning and floor structures in Wandsworth, 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 openings in SW15 mansion blocks to replacement joists and supported openings in Balham and Tooting period flats, GS Renovation delivers structural alterations across Wandsworth. Our founder's 30+ years on the tools mean we understand how these red-brick blocks and purpose-built flats are put together, and how to change them safely within the Building Regulations.
In Wandsworth, 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 Wandsworth.
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 Wandsworth address and an itemised quote.
- The engineer we appoint designs the work, and it is registered with Wandsworth 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 Wandsworth homes
Structural alterations cover far more than knocking a wall through. Across Wandsworth we form new door and window openings in solid masonry, replace tired or overloaded floor joists in older period flats, create supported openings between reception rooms, and underpin where ground movement has taken its toll. Riverside developments near the Thames and the older stock around Wandsworth Common each behave differently, so we tailor the approach to the building rather than repeating a formula.
Every alteration is designed by a structural engineer before we start. New openings receive a correctly sized steel lintel or beam bearing onto padstones, temporary propping holds the load while we work, and demolition follows a careful staged sequence. Replacement joists are specified for span and spacing, and supported openings get the right bearing at each end. Wandsworth Council's building control inspects the stages and certifies the finished work under the Building Regulations.
Housing in Wandsworth
Of the 157,900 homes the valuation list records in Wandsworth, 43% were built before 1919, 7% between the wars and 49% since 1945; 72% are flats and 28% are houses. Structural repair to a block in Wandsworth usually falls to the freeholder under the lease, so it is agreed with them before anything is opened up, which matters here because most homes are flats.
Digging down in Wandsworth under the Local Plan basement policy
Some structural alterations in Wandsworth go below the ground floor: lowering a cellar floor to get standing height, or digging out beneath a period house to add a room. Where that creates or extends a basement, Wandsworth Local Plan Policy LP6 applies. It permits a new or extended basement only where it results in no more than one storey of basement accommodation below ground level. It also limits a residential basement to no more than 50% of the existing rear garden land or other undeveloped garden area. The size of the dig is set by the policy first, then the structural engineer we appoint designs the underpinning and retaining walls to suit it.
Where any part of the basement runs under the garden, LP6 requires a minimum of 1 metre of naturally draining permeable soil above it, together with a minimum 200mm drainage layer. That fixes how deep the roof slab under the lawn has to sit, and so how far down the excavation goes. Wandsworth's basement extensions guidance also strongly encourages a Construction Method Statement, which is a requirement for listed buildings and must be independently verified. On a Wandsworth terrace the same statement is useful to the adjoining owners, so it is written alongside the engineer's design rather than after the planning decision.
Underpinning and openings across SW12 and SW17
Parts of Wandsworth sit on London clay that shrinks and swells with the seasons, and older flats around SW12 and SW17 occasionally show the cracking and movement that calls for underpinning. We work to the engineer's scheme, excavating and casting in controlled bays to deepen the foundation without undermining what stands above. Where the underpinning or a new opening affects a wall shared with the neighbouring flat or house, the Party Wall Act applies and you serve notice first as building owner, using the engineer's drawings we supply.
Leasehold coordination runs alongside the structure. We secure the freeholder's licence to alter, agree method and hours with the managing agent, and keep neighbouring residents informed while props and steel are in place. It is worth being clear that this internal structural work is governed by building regulations, not planning permission. Planning is about the outside of the building, and a conservation area narrows what can change there without permission. A listed building is different: it needs listed building consent for internal structural work too, which we will flag early if it applies to your block.
- Underpinning and foundation strengthening in sequenced bays
- Crack repair, helical bar stitching and masonry restraint
- Load-bearing wall removal and new structural openings
VOA Council Tax stock of properties, March 2025, for all 38 statistical areas in Wandsworth. Counts rounded by the VOA.
The GS Renovation Difference in Wandsworth
GS Renovation handles Wandsworth structural alterations as one joined-up job, not a scatter of trades. The engineer we appoint designs the openings, joists or underpinning; we help you secure the freeholder's consent, give you the drawings for any party wall notice you serve, build the work and carry building control through to the completion certificate. Occupied flats stay clean and protected while we work, and our founder's 30+ years on the tools mean the detailing is right first time.
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 Wandsworth
Do you charge for a survey before quoting structural alterations in Wandsworth?
GS Renovation charges nothing to survey an SW18 property for structural alterations, because pricing structural alterations in Wandsworth unseen is guesswork. The visit confirms the scope, what approvals it needs (building regulations approval of the engineer's design), and where in £1,500 to £21,000 or more, from a simple opening to underpinning one elevation (indicative) the job sits. An itemised figure follows in writing. Call 07472 424 226 or email info@gsrenovationltd.co.uk.
My Wandsworth flat has cracks appearing. Do I need underpinning?
Not always. Cracking can come from clay movement, but also from lesser causes that need only monitoring or repair. We arrange a structural engineer's assessment first to find the real cause. If underpinning is genuinely required, the engineer designs it and we cast it in controlled bays. You serve party wall notice on affected neighbours as building owner, using the engineer's drawings, and Wandsworth building control inspects and certifies the work.
Can I widen the back opening of my Wandsworth house onto the garden?
Usually, with steel over the new width and something solid at each end. Where the brick piers left either side are too slender to take the load, the engineer may specify a steel goalpost frame instead, standing on its own foundations. Forming or widening an opening in an external wall needs Building Regulations approval, and Wandsworth Council building control inspects before the steel is covered.
Does changing the roof structure of my Wandsworth house need approval?
Yes, if it alters anything that carries load. Removing purlin struts, cutting ceiling ties or taking out a loft wall changes how the roof is held up, so an engineer's design and Building Regulations approval come first. It is common for older Wandsworth roofs to have been altered before, so the loft is surveyed carefully to see what previous work left behind.
Can a new doorway be cut through an internal wall in my Wandsworth home?
Yes, but a load-bearing wall still needs a lintel sized for what sits above, even for a single door. The masonry is propped with strongboys, the opening is cut, and the lintel is bedded on each side before the props come out. It is Building Regulations work, so it needs notifying even though the opening is small, and the lintel is inspected before plastering.
How do structural alterations differ in a Wandsworth riverside development?
In a modern concrete-framed block, the floor slabs, columns and core walls carry the load, so many internal walls are lightweight partitions that come out without steel. The difficulty moves elsewhere: cutting a hole through a slab or core wall is a serious structural change needing the engineer's approval and the freeholder's consent. Services are often cast into the floor, so drawings come first.
Does clearing an old outbuilding in a Wandsworth conservation area need planning permission?
It can. In a Wandsworth conservation area, planning permission is required to demolish completely or substantially an unlisted building of 115 cubic metres in volume or more. A large garage or workshop cleared to make room for new structural work can reach that size, so it is measured before the demolition is programmed. Wandsworth has 46 conservation areas, ranging from a short street such as Deodar Road to a large area such as West Putney, so check the conservation area map for your address first.
Is a house on the Wandsworth local list treated differently for structural work?
Inside the house, generally not: the beams, underpinning and new openings remain a building regulations matter. Wandsworth's local list was produced in 1983, has been added to since, and had its last big review in 2018. Being on it matters when structural work changes the outside and needs planning permission, because the application then has to weigh the building's local interest. Check the list before the engineer draws anything visible from the street.
What does Wandsworth pre-application advice offer before a basement or underpinning scheme?
Wandsworth's householder pre-application service offers either a meeting and written advice, or a meeting only of up to 1 hour. For a dig controlled by LP6, the written version is the one worth having, because it records what officers said about the basement's extent and can be passed to the engineer and the neighbours. Take a measured survey and a section through the garden to the meeting, since the share of garden used and the soil depth above the basement are among the things the policy tests.
Every Service, One Team
More GS Renovation Services in Wandsworth
One team for every GS Renovation service in Wandsworth:
Same Service, Nearby Areas
Structural Alterations Near Wandsworth
We carry out structural alterations across Wandsworth and the surrounding areas. Explore a nearby location:
Ready to Start Your Wandsworth Project?
Free, no-obligation quote for structural alterations in Wandsworth.