Structural Alterations New Cross
Structural alterations, new openings, underpinning and floor structures in New Cross, 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 throughout New Cross and neighbouring Deptford, Peckham and Brockley. Across SE14's Victorian and Edwardian terraces and converted flats we form new openings, replace tired joists, install supported openings and underpin where the ground has moved, all engineer-designed and signed off. Our founder's 30+ years of building experience stands behind every calculation.
In New Cross, 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 New Cross.
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 New Cross address and an itemised quote.
- The engineer we appoint designs the work, and it 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 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 across New Cross homes
The terraced stock around New Cross throws up a predictable set of structural jobs. Rear closet wings and side returns invite new openings into the kitchen; original softwood joists in the reception floors sometimes need replacing after decades of notching for pipes and cables; and wider openings between rooms call for a supported beam rather than a simple lintel. We match the solution to what the house is actually doing, not to a standard template.
Every alteration begins with a structural engineer who calculates the loads and specifies the steel. Beams are sized for the span, seated on padstones and propped while we work. Where an original bay or a bearing wall has settled, underpinning stabilises the foundation before we build on it. The principle is constant across SE14: understand the load path first, then support it permanently before removing anything.
Housing in New Cross
Of the 12,080 homes the valuation list records in New Cross, 43% were built before 1919, 2% between the wars and 49% since 1945; 72% are flats and 28% are houses. Where most homes are flats, structural repair to a block in New Cross usually falls to the freeholder under the lease, so it is agreed with them before anything is opened up.
Lowering a New Cross cellar: plan it as basement development
Some of the Victorian houses in New Cross, where 43% of homes were built before 1919, have a cellar under the front room. Lowering its floor to make a habitable room means digging below the existing footings, and Lewisham Local Plan Policy QD9 requires proposals for basement development to include a Basement Impact Assessment. Treat a cellar lowering as basement development from the outset and ask Lewisham to confirm. The plan says the assessment must be carried out by a suitably qualified and recognised independent assessor and paid for by the applicant, so that appointment sits alongside the structural engineer we appoint, who designs the underpinning.
The same policy says basement work must not adversely impact on the structural stability of the host building, neighbouring properties, infrastructure and the public realm, taking into account local geology. On a New Cross terrace the neighbouring properties are joined to yours, and 25% of homes here are terraced houses. The footing under the party wall is shared, so underpinning it is work to the neighbour's structure too. The building owner serves party wall notices once the sequence of underpinning bays is designed, and the assessor's report deals with the house next door as well as your own.
Consents and controls in Lewisham
Internal structural alterations are governed by the Building Regulations, so Lewisham Council's building control or a registered building control approver reviews the design, inspects the steelwork and bearings, and certifies the finished job. This is not a planning matter. Planning is about the outside of a building, so alterations inside an unlisted New Cross terrace proceed on a building regulations basis alone, in or out of a conservation area; a listed one also needs listed building consent.
Because these terraces share party walls and chimney stacks with the houses either side, alterations that cut into or bear onto that shared wall are notifiable under the Party Wall Act. You serve the notices on your neighbours as building owner before starting, with the drawings we supply. From the engineer's drawings through underpinning, new joists and supported openings to the final certificate, one team keeps the whole process moving and documented.
- Party wall process explained, and work built to the award
- Structural engineer appointed and coordinated for the design
- Underpinning and foundation strengthening in sequenced bays
VOA Council Tax stock of properties, March 2025, for New Cross Gate, New Cross South and Telegraph Hill. Counts rounded by the VOA.
Trusted Structural Alterations in New Cross
For structural alterations in New Cross, GS Renovation gives you a single accountable contractor. We commission the engineer, handle Lewisham building control, and carry out the work, from replacement joists to underpinning and supported openings. Careful propping, tidy working in your occupied SE14 home and our founder's 30+ years of structural experience mean the job is done once and done right.
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 New Cross
Why do structural alterations quotes in New Cross vary so much?
Variation in structural alterations quotes across New Cross almost always comes from what has been left out. GS Renovation prices structure, trades, approvals and reinstatement after an SE14 survey, so the total can look higher than a quote covering half of it. The honest range is £1,500 to £21,000 or more, from a simple opening to underpinning one elevation (indicative), and the ground and existing foundations decide whether underpinning is needed, which a quote without a survey cannot know.
Do I need planning permission for structural alterations inside my New Cross house?
Almost never for internal work. New openings, replacement joists, supported openings and underpinning are controlled under the Building Regulations, and Lewisham building control signs them off. Planning permission is about external alterations; inside, the exception is a listed building, which needs listed building consent. We confirm which consents your specific SE14 project needs and handle building control for you.
Can a new opening be formed in the closet wing wall of a New Cross house?
Usually, but the wing is where the house is weakest, so it is checked more carefully than the main walls. Closet wings in the local terraces were often built more cheaply, sometimes on shallower footings, and cracking tends to appear where the wing meets the main house. The engineer looks at that junction and the foundation before designing the lintel or beam for the new opening.
Can structural alterations be made in a converted New Cross flat?
Yes, though you own less of the structure than it seems. In a house split into flats, the floors, the outside walls and the loadbearing partitions usually belong to the freeholder and carry other people's homes. The lease normally requires written consent before structural work, and an engineer designs for the building as a whole. Lewisham Council building control, or a registered building control approver, then signs it off.
When does a crack in a New Cross house actually need underpinning?
Only when the engineer is satisfied the movement is ongoing and the footing cannot cope. On London clay, old cracks can be historic and stable, so monitoring often comes before any decision. If underpinning is needed, it goes in short bays. Because those bays usually go deeper than the adjoining footing close to the boundary, next door is served notice a month ahead.
Do notched joists in a New Cross terrace need replacing during alterations?
Not always, but they must be assessed. Generations of plumbers and electricians have cut into the floor joists of SE14 houses, sometimes deep notches mid-span where they do most harm. With the floor up, the engineer decides whether a joist can be strengthened by bolting new timber alongside or must be replaced, and new services are routed through properly positioned holes instead.
Does underpinning a New Cross house near a drain need the water company's agreement?
It can. Lewisham's building control guidance says you must apply for a build over agreement before doing any works if your home is within 3 metres of a public drain or 1 metre of a public lateral drain. Behind a terrace the drain run shared by several houses may be public. A camera survey shows where it runs before the structural engineer we appoint sets out underpinning bases, so the agreement is applied for at design stage rather than when a pipe appears in the trench.
Does structural work on a locally listed New Cross building need a heritage statement?
Where the work needs planning permission, yes. Lewisham requires a heritage statement for all planning applications affecting buildings in conservation areas and listed buildings, both nationally listed and locally listed. Its Local List has over 250 entries, with the most recent additions made in March 2020. Where a new opening on an outside wall or a rebuilt rear wing of a building on that list needs permission, the statement explains the effect on the building, so check the list before the design is drawn.
Does turning a New Cross cellar into a separate flat bring the Community Infrastructure Levy?
Ask before costing it. Lewisham's CIL charging schedule was adopted on 25 February 2015, and CIL has been levied on liable new developments since 1 April 2015. Its rates table sets a charge per square metre for Use Class C3, which covers homes. A cellar that becomes a separate flat is a new dwelling, which needs planning permission, so the question of liability should go to Lewisham at the planning stage. A lowered cellar that stays part of the house is a different case.
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