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Extensions & Structural Building Work in Bromley

House Extensions in Bromley, London

Extending a Victorian terrace, Edwardian semi or ex-council maisonette means forming a new structural opening into a house that predates modern Building Regulations. We handle the structural engineer, Building Control route and Party Wall Act 1996 process together, from rear and side-return extensions through to full two-storey additions.

Bromley overview

House Extensions in Bromley

South East London's largest borough by area, with established period housing and demand for roof replacement and general repairs. Bromley falls well within the South East London ground Lian Construction covers on a regular basis. For rear, side-return, wraparound and two-storey house extensions with structural engineering and Party Wall compliance in Bromley, that local knowledge means fewer surprises once work is on site and a team that already understands the borough's typical property stock.

Bromley is South East London's largest borough by area, and that scale shows in the range of period housing across it. Expect a good deal of Victorian and Edwardian terraced and semi-detached houses in the more established residential pockets, alongside a substantial stock of 1920s and 1930s suburban semis, which is typical of outer London boroughs that grew up around expanding rail links in that era. There are also pockets of larger interwar and postwar detached houses, plus some later 20th-century infill and estate development filling in the gaps between older neighbourhoods. Roofs, chimneys, brickwork and rainwater goods on this older stock are now well past their original design life in many cases, which is a big part of why roof replacement and general repair work is in steady demand across the borough. Because Bromley covers such a wide area, the age and condition of housing can vary a lot street to street, so it is worth getting a property looked at individually rather than assuming what worked next door applies to your own roof or structure.

Given how much ground Bromley covers as London's largest borough, demand for roofing and general repair work is spread thinly across a wide area rather than concentrated in one or two hotspots. That has practical implications for homeowners: it can be harder to find a contractor who is genuinely local to your specific part of the borough and willing to travel efficiently, and lead times can stretch out during busy periods simply because tradespeople are covering more ground between jobs. With so much established period housing, a lot of the work coming through is reactive, roof repairs after storm damage, ongoing maintenance on ageing chimneys and guttering, and general fabric repairs on houses that were not built with modern weatherproofing standards in mind. For homeowners and landlords, this usually means being proactive pays off: getting a roof or exterior condition checked before a leak forces an emergency call tends to be cheaper and less disruptive. It is also worth asking any contractor how familiar they are with the specific area of Bromley you are in, since access, parking and the age profile of housing can differ quite a bit across such a large borough.

Given the amount of established period housing across Bromley, it is worth checking early whether a property sits within a conservation area, as is the case in parts of many outer London boroughs with older housing stock. This can affect what is permitted for roof coverings, chimney alterations, and visible external repairs, sometimes requiring like-for-like materials or additional consent even for straightforward repair work. Not every period property will be affected, and many repairs fall under permitted development, but it is not something to assume either way. If a property is listed or in a conservation area, it is sensible to confirm requirements with the local planning authority before work starts, since retrospective consent issues can cause delays and added cost. A contractor experienced with older properties should be able to flag likely restrictions early, but the homeowner remains responsible for confirming planning status.

Typical house extensions prices in London
ItemTypical range
Single-storey rear extension (per m²)£3,000–£5,000
Side-return / wraparound extension (per m²)£4,500–£5,500
Two-storey extension (per m²)£2,800–£4,200
Structural opening / RSJ steel beam£1,800–£4,500+

General London market guidance, not a fixed quote — actual pricing depends on a site survey. Full breakdown: cost guide.

Party Wall etc. Act 1996 on a Shared Terrace or Semi

If your extension involves a shared party wall - which almost every Victorian or Edwardian terrace or semi-detached extension does - or excavation within 3m or 6m of a neighbour's foundation depending on how deep your new foundations go, the Party Wall etc. Act 1996 requires you to serve formal notice before work starts. For work directly on the party wall itself you need two months' notice; for adjacent excavation it's one month. If your neighbour doesn't respond or dissents, you end up in a schedule of condition survey and a formal Award process with a party wall surveyor. Party wall surveyor cost in London typically runs £900-£2,000 where both sides agree a single surveyor, rising to £2,000-£3,000+ if each side appoints their own. This cost is borne by you as the building owner carrying out the works, not split with the neighbour. Starting groundworks before the notice period has run, or without an Award in place where one's needed, leaves you exposed to an injunction that can stop the job entirely and is one of the most common causes of a stalled extension in London. On extension jobs we serve the notices and coordinate the surveyor as part of the build programme, rather than as an afterthought once excavation is already close to the boundary.

How Long a London Extension Takes, Start to Finish

From first site visit to final sign-off, the pre-construction phase - the measured survey, design, structural engineering, deciding the planning route, the Building Control submission and any Party Wall Act notice period - commonly takes in the region of 2-4 months before groundworks even start, and this is where projects most often get compressed unrealistically in initial planning. Once on site, a straightforward single-storey rear extension under permitted development with a Building Notice typically runs somewhere around 12-16 weeks as a planning guide, once the design is settled and the structural engineer's calculations are in hand, though exact timing depends on your specific design and site conditions. A side-return or wraparound extension on a terrace usually adds a further 2-4 weeks to that build programme because of the underpinning work to the party wall foundation and the narrower access for materials and skips. A two-storey extension typically runs longer again, in the region of 16-22 weeks on site, because of the additional floor structure, the roof tie-in at first-floor level, and doubled first and second fix. None of these figures include a full planning application if one's needed, which can add roughly 8 weeks or more before groundworks start - and the Party Wall Act's two-month notice period (one month for adjacent excavation) runs in parallel with design and Building Control preparation where it's handled properly, instead of being tacked on afterwards. Served at the same time as your Building Control application it costs you no extra time overall, but served late, or if a neighbour appoints their own surveyor and negotiations drag, it can add real weeks to a job that's otherwise ready to start. Weather affects roofing and groundworks stages more than any other phase, which is why we sequence those for drier months where the programme allows it.

Structural engineer sizes every steel beam and padstone before we price the job, catching problems Building Control would otherwise reject later
One team runs the structural engineer, Building Control application and Party Wall Act 1996 process together rather than as three separate chases
We advise Full Plans versus Building Notice based on your specific job's risk, not a default answer
Regular coverage of Bromley and the wider South East London area

Signs to look for

Do you need house extensions in Bromley?

  • There's visible evidence of a botched earlier extension on the property - a cold stripe of mould along a roof-to-wall junction, a damp patch where a patio's built up against the original wall - and you need it diagnosed and corrected as part of any new work
  • Your kitchen or living space is genuinely too small for how the household actually uses it day to day, not just cosmetically dated
  • You've outgrown a two- or three-bed Victorian/Edwardian terrace or ex-council flat, but moving in Zone 2-4 London would cost more in stamp duty and fees than extending the current property
  • You're relying on a side-return, alley or awkward rear garden as dead storage space rather than usable floor area

How the work is handled in Bromley

  1. Step 1Initial site visit and measured survey of the existing house, boundary lines, drainage runs and nearby trees, checked against permitted development limits and the borough's conservation area / Article 4 status
  2. Step 2Design and route decision - permitted development, Larger Home Extension Scheme prior approval, or full planning permission
  3. Step 3Structural engineer appointed to size steel beams, padstones and foundations and produce calculations for Building Control
  4. Step 4Building Control application submitted - Full Plans (formal approval in 5-8 weeks) or Building Notice (start in 2 days, no prior sign-off) - decided on the specific job's structural and ground-condition risk
  5. Step 5Party Wall etc. Act 1996 notices served on affected neighbours where a shared wall or nearby excavation applies, run in parallel with Building Control rather than after it
  6. Step 6CCTV drainage survey and, where needed, a build-over agreement application to the water company before foundations are dug
  7. Step 7Groundworks - trial pits, foundation excavation and pour sized to the actual ground conditions and agreed depth
  8. Step 8Structural steel installed and the opening formed between the existing house and new extension, with temporary propping as needed
  9. Step 9Superstructure built with particular attention to insulation continuity at the wall-to-roof and wall-to-existing-house junctions
  10. Step 10Windows, doors and roof glazing fitted to current Part L standards, followed by first-fix electrics and plumbing
  11. Step 11Building Control inspections at foundations, DPC/membrane, drainage and insulation stages, through to completion certificate
  12. Step 12Second fix, decoration and snagging, confirming the new damp-proof membrane is properly lapped with the original house's DPC before ground levels are finished

Questions

House Extensions questions in Bromley

How quickly can Lian start rear, side-return, wraparound and two-storey house extensions with structural engineering and Party Wall compliance in Bromley?

Bromley is part of our regular South East London coverage, so once we've surveyed the property we can usually confirm a start date quickly. Send the address and scope and we'll arrange the next step.

Do you cover all of Bromley?

Yes. Bromley falls within the area Lian Construction serves across Greater London.

How do I know if my roof needs replacing or just repairing in Bromley's older housing?

It usually comes down to the extent of the damage and the age of the roof covering. A handful of slipped tiles or a localised leak can often be repaired. But if a roof is showing widespread wear, sagging, or repeated leaks in different spots, replacement tends to be more cost-effective long term than patching it repeatedly. Given how much period housing there is across Bromley, an on-site inspection is really the only reliable way to tell, since roof condition varies a lot even between similar-looking houses.

Do I need planning permission for a house extension in London?

Not necessarily - a single-storey rear extension up to 3m deep (terrace/semi) or 4m (detached) generally falls under permitted development, and up to 6m/8m via the Larger Home Extension Scheme prior approval route, a lighter-touch neighbour notification through the council rather than a full application. But conservation area status or an Article 4 Direction, both common across London boroughs, can remove permitted development rights entirely, meaning even a modest extension needs a full planning application with an 8-week (or longer, for larger schemes) decision timeline - we check this against your borough's specific status at the first site visit.

What is the Larger Home Extension Scheme?

It's the prior approval route under permitted development that lets a single-storey rear extension go beyond the normal 3m/4m depth limit, up to 6m for a terraced or semi-detached house or 8m for a detached house. Rather than a full planning application, the council runs a lighter-touch neighbour consultation and issues a decision, with a statutory determination period of around six weeks. It still isn't available everywhere - conservation areas and Article 4 Directions can remove the right to use it, in which case a full planning application is the only route regardless of the extension's depth.

What's the difference between a Full Plans application and a Building Notice?

Full Plans means submitting detailed drawings and structural calculations to Building Control for formal approval before work starts, typically taking 5-8 weeks but giving you sign-off on the design in advance. A Building Notice lets you start on site as little as 2 days after submission, but without prior approval, so any structural or compliance issues get picked up during site inspections rather than beforehand. We generally recommend Full Plans for anything with more structural or ground-condition risk - a side-return with underpinning, a two-storey addition, unusual soil conditions - and reserve Building Notice for simpler, well-understood openings where starting sooner carries no meaningful added risk.

Talk to Lian Construction about Bromley

Send the site address in Bromley, photos if available, and the house extensions work you need. We can review the scope and arrange the next step.

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