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Extensions & Structural Building Work in Hammersmith and Fulham

House Extensions in Hammersmith and Fulham, 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.

Hammersmith and Fulham overview

House Extensions in Hammersmith and Fulham

West London borough with high-value period conversions where quality finishing work — tiling, plastering, decorating — matters most. Hammersmith and Fulham falls well within the West 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 Hammersmith and Fulham, that local knowledge means fewer surprises once work is on site and a team that already understands the borough's typical property stock.

Hammersmith and Fulham's housing stock is dominated by the kind of period property found across much of inner and West London: Victorian and Edwardian terraces and villas, many of which have been split into flats over the decades, alongside mansion blocks and some purpose-built conversions from the early to mid-20th century. A significant share of the borough's homes are conversions rather than single-family houses, which is typical of high-value West London areas where large period houses have been reworked into two, three or more flats to meet demand. This conversion history means a lot of the existing stock carries older wall and floor build-ups, original plasterwork in varying condition, and layouts that have been altered more than once. As with other West London boroughs, there's also a mix of ex-local authority blocks and post-war infill alongside the period stock. Because so much of the housing is period conversion rather than new-build, quality of finish tends to matter more here than in areas with a higher proportion of modern construction, since old walls, ceilings and floors need careful preparation before tiling, plastering or decorating will look right and last.

In a borough where so much of the property is high-value period conversion, the finishing trades carry more weight than they might elsewhere. A flat carved out of a Victorian terrace lives or dies on how well the plaster, tiling and decorating are done, since buyers and tenants at this end of the market notice uneven walls, poor tile lines or rough paintwork more readily than they would in a standard new-build. That creates steady demand for contractors who can do finishing work properly rather than just quickly, particularly on bathroom and kitchen refits where tiling quality is hard to hide. It also means homeowners and landlords doing up a conversion flat are often better served focusing budget on getting the finishing right rather than cutting corners to save on the last stage of a project. For landlords specifically, a well-finished conversion tends to let faster and at a better rent in this kind of market, so the extra cost of proper plastering and tiling work is usually recovered over time. Given the age and variability of the underlying building fabric, it's also worth budgeting some contingency for making good old walls and floors before the visible finishing work even starts.

Given how much of Hammersmith and Fulham's housing stock is period conversion, it's worth being aware that conservation area and listed building rules are common across this type of West London property, as they are in many inner London boroughs. Converting or altering a period house can trigger planning or listed building consent requirements depending on the specific property and area, particularly for external changes, window replacements or work affecting original features. Internal finishing work like plastering, tiling and decorating is generally more straightforward from a planning perspective, but if it's part of a wider conversion or alteration project it's sensible to check the property's status with the council before starting. As with any older building, it's also worth confirming what internal fabric might be original or protected before stripping back walls, since this can affect both the approach and the cost of the finishing work.

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.

Building Control: Full Plans or Building Notice

Separately from planning permission, every extension needs Building Control sign-off under the Building Regulations 2010, and there are two routes to get it: a Full Plans application, where detailed drawings and structural calculations are submitted and formally approved before work starts, typically taking 5-8 weeks; or a Building Notice, where you can start on site as little as 2 days after submission but without prior approval of the design, meaning any problems get picked up on site inspections instead of on paper beforehand. For a straightforward single-storey rear extension with a well-understood structural opening, a Building Notice can be the faster, lower-friction route. For anything with more structural or ground-condition risk - a side-return with underpinning, a two-storey addition, unusual soil conditions, or a design close to the boundary - we generally recommend Full Plans, because getting the steel sizing and foundation design checked and approved before you dig avoids a stop-work order mid-excavation if Building Control isn't satisfied. Part A covers structural stability, Part L sets the thermal performance targets for the new walls, roof, windows and doors and caps how much of the extension's floor area can be glazed, and Part H4 requires water company approval for any foundation within 3m of a public sewer. We decide the route with you at the design stage based on the specific job, not as a default answer.

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.

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 Hammersmith and Fulham and the wider West London area

Signs to look for

Do you need house extensions in Hammersmith and Fulham?

  • A growing or multi-generational household needs an extra bedroom or bathroom that a two-storey extension could add above a ground-floor extension
  • You've had conflicting advice about whether your project needs full planning permission, prior approval, or falls under permitted development, and nobody's checked your borough for an Article 4 Direction or conservation area status
  • A previous quote priced the job without mentioning a structural engineer, a soil or trial pit assessment, or a Party Wall Act process - on a terraced or semi-detached house that usually means the price is wrong or incomplete
  • 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

How the work is handled in Hammersmith and Fulham

  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 Hammersmith and Fulham

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

Hammersmith and Fulham is part of our regular West 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 Hammersmith and Fulham?

Yes. Hammersmith and Fulham falls within the area Lian Construction serves across Greater London.

Do landlords in Hammersmith and Fulham need to do more than a basic paint-and-carpet refresh between tenancies?

It depends on the property and the rent bracket you're aiming for. In higher-value conversions, tenants and agents often expect a more finished look, so scuffed plaster or patchy paintwork can affect how quickly a flat lets and at what price. A basic refresh may be fine for a lower-value let, but for period conversions competing at the top of the market it's usually worth budgeting for proper finishing rather than the minimum.

Why use Lian Construction rather than separate trades?

Lian Construction acts as a single accountable contractor for the whole extension, coordinating the structural engineer, the Building Control submission, and - where needed - the Party Wall surveyor as one sequenced process rather than you separately chasing three professionals who aren't talking to each other. We build extensions across London and into the surrounding Home Counties, and currently hold 26 five-star reviews on our Google Business Profile, built through completed jobs and organic word of mouth rather than paid advertising.

How much does a house extension cost in London in 2026?

A single-storey rear or side extension typically costs £3,000-£5,000 per square metre all-in, including VAT, the structural engineer and Building Control fees, so an 18-20m² kitchen extension usually lands around £55,000-£95,000. Side-return and wraparound extensions on Victorian and Edwardian terraces run higher, roughly £4,500-£5,500/m², because of party wall underpinning, narrow rear access and longer steel spans. Two-storey extensions are often cheaper per square metre, around £2,800-£4,200/m², because the foundation and roof cost is shared across two floors, though total project cost is usually higher in absolute terms, commonly £120,000-£200,000+.

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.

Talk to Lian Construction about Hammersmith and Fulham

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

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