Structural Alterations Highgate
Structural alterations, new openings, underpinning and floor structures in Highgate, 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 Highgate, in the Victorian and Edwardian houses, many now flats, that fill the N6 streets between Hampstead Heath and Kentish Town. We form new openings, replace tired joists, underpin where foundations need it and install supported openings, all designed by the structural engineer we appoint, propped and built by us, and signed off by building control.
In Highgate, 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 Highgate.
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 Highgate address and an itemised quote.
- The engineer we appoint designs the work, and it is registered with Camden 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 work in Highgate's older homes
Alterations in Highgate's period stock cover a wide range: cutting a new opening into a closet wing, replacing joists that have sagged or suffered damp in a rear return, or underpinning a corner where the original shallow Victorian foundations have moved. Each starts with a structural engineer specifying the fix, whether that is a beam and padstones for a new opening or a sequence of underpinning bays for the foundations.
The side returns and rear closet wings typical of these houses are where much of this work happens, as owners open kitchens into them or repair walls that have settled over a century. We prop, work in staged sections and keep the surrounding structure stable throughout, which is essential in homes where the party walls and upper floors depend on what sits below.
Housing in Highgate
Around 10,090 homes make up Highgate on the valuation list; 69% are flats and 31% houses, and 47% date from before 1919, 24% from between the wars and 28% from after 1945. Structural repair to a block in Highgate 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.
A basement on a sloping Highgate plot under Camden's rules
31% of Highgate homes are houses, and on a plot that falls away, digging out below the house can look like easy space. Camden's Article 4 direction on basements, adoption date 1 June 2017, applies to the whole borough, so every basement excavation needs planning permission, and the application must include a Basement Impact Assessment specific to the site and proposal. On a slope that assessment has more to explain than on level ground: water moving through the hill, the neighbour uphill whose foundations sit higher than the new floor, and the retaining walls that end up holding the difference.
Camden Planning Guidance: Basements limits development to one storey deep and to no more than 50% of the garden of the property. On a stepped site the excavation depth changes across the footprint, and the guidance measures a storey as the total depth of the excavation, so ask the structural engineer we appoint for the depth at the deepest point, not the average. The guidance also strongly recommends that Party Wall agreements are concluded before the Basement Construction Plan is submitted for approval. As building owner you serve those notices, so they go out once the engineer's underpinning sequence exists.
Supported openings and sign-off in N6
A supported opening means a steel or timber lintel carrying the wall above onto padstones, with temporary props holding everything while it is formed. In N6 houses the wall being opened is frequently a spine wall or a party wall, so the engineer's design accounts for the loads it carries and, where the party wall is involved, you serve notice on the neighbour under the Party Wall Act before work starts, using the drawings we supply.
All of this is Building Regulations work rather than planning, so building control at Camden or Haringey, depending on your address, inspects the propping, the bearings and the finished structure. Planning permission only arises where the outside of the house changes, such as a new opening in an external wall, and a listed house also needs listed building consent for internal structural work. We appoint the engineer and book every building control inspection, so the whole job runs as one coordinated programme.
- Wall plate, joist hanger and restraint strap installation
- New door and window openings in solid masonry
- Party wall process explained, and work built to the award
VOA Council Tax stock of properties, March 2025, for Highgate West, Highgate East and Highgate Wood. Counts rounded by the VOA.
Why Choose GS Renovation in Highgate
For structural alterations in Highgate, GS Renovation gives you one team accountable for the whole job. We commission the engineer, give you the drawings and programme for any party wall notice you serve, arrange building control sign-off and carry out the propping and works cleanly in an occupied home. Underpinning, new openings, replacement joists or supported openings, all delivered with the care our founder's 30+ years on the tools brings.
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…
It's the second time I have hired George and he has been absolutely professional and the work he did resembles perfectly what I had in mind. Being an…
FAQ
Frequently Asked Questions about Structural Alterations Highgate
What does the structural alterations quotation for a Highgate home cover?
A Highgate quotation for structural alterations sets out scope, programme and price on one document, within £1,500 to £21,000 or more, from a simple opening to underpinning one elevation (indicative). It shows what is done, in what order and at what cost, and the order is not arbitrary: the engineer's design is issued before the building control application. Exclusions are stated plainly rather than left to be discovered once work starts at the N6 property.
Do I need planning permission for structural alterations inside my Highgate house?
Internal structural work such as new openings, replacement joists or underpinning is covered by the Building Regulations and inspected by building control at Camden or Haringey, not by planning. Planning permission only comes into it if the exterior changes, and a listed property also needs listed building consent, even for internal work. We confirm which applies to your N6 home and handle the building control approval throughout.
What triggers underpinning at a Highgate property?
Evidence that the foundations are still moving, not cracks on their own. Victorian houses in Highgate often stand on shallow footings, and a corner can drop where a drain leaks or a tree draws moisture out of the ground. The engineer looks for the cause and, if movement continues once it is fixed, designs underpinning in short bays. Digging within 3 metres of a neighbour to below their footings needs one month's notice.
Can I make a new opening in the external wall of my Highgate flat?
Only with several consents lined up. The external walls of a block or converted house are normally retained by the freeholder, so the lease requires their written agreement, and a new window or door changes the elevation, which for a flat, or in a conservation area, needs planning permission from Camden or Haringey too. Structurally, the engineer sizes a lintel for whatever the wall carries, and building control inspects it before it is closed in.
What happens if joists in my Highgate home turn out to be rotten?
They are cut back to sound timber and replaced, or supported with new timbers bolted alongside, to the engineer's specification. Rot at joist ends usually means water has been getting into the wall from a leaking gutter, a bridged damp course or blocked airbricks, so that cause is fixed first. Where the damage sits under a bathroom, the waste pipes and tanking above are checked before the new floor goes down.
What if my Highgate home is in a listed building?
Then internal structural alterations need listed building consent from Camden or Haringey as well as building regulations approval, and the two are applied for separately. The consent application shows what historic fabric is affected, and changes are judged on how they alter the plan and surviving features. Allow for it before the engineer's design is final, because the consent can shape where openings go and how wide they are.
Is Camden's specialist review of a Basement Impact Assessment worth it for a Highgate slope?
On a sloping site, yes. Camden offers specialist pre-application advice that reviews a Basement Impact Assessment before the planning application goes in. On a Highgate slope, groundwater and the stability of the ground uphill are what the assessment has to answer. A review at that stage tests the ground investigation and the retaining design while they can still be changed cheaply, rather than after a refusal.
How big can a basement under a Highgate house be compared with the house?
Camden Planning Guidance: Basements says a basement should be less than 1.5 times the footprint of the host building in area, and no more than one storey deep. On a Highgate house with a rear garden, the garden limit may bite first, since the basement must not exceed 50% of the garden. Measure the house footprint and the garden before any architect draws rooms, because those two figures set the envelope.
Does Camden band its building control charge for underpinning a Highgate house?
Yes. Camden's Schedule 2 residential charges include a band for underpinning up to 10m in length. On a Highgate house that has moved at one corner, the engineer's drawing should state the length of wall to be underpinned, because that length decides the band. Where the investigation later extends the run, tell building control before the extra bays are dug, so the charge and the inspections follow the actual work.
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