Five boroughs. Five planning authorities. Five sets of estate consent regimes, logistics constraints, and construction rules that change the cost and programme of every project. The calculator accounts for borough. So does the PCSA.
RBKC’s borough-wide Article 4 Direction removed permitted development rights for basements in 2016. Every below-ground project requires a full planning application, no exceptions.
Conservation area coverage exceeds 70% of residential streets. The 2015 Basement Development Supplementary Planning Document limits most properties to a single-storey basement beneath the existing footprint — full planning application required, with no permitted development fallback. Listed building density is among the highest in London. Internal works to listed properties require Listed Building Consent covering every original feature: cornices, fireplaces, floor joists, internal doors. Not just the facade. RBKC’s planning determination period for a standard application runs eight weeks. Basement applications with a mandatory Construction Management Plan typically take twelve to sixteen weeks. Add party wall timelines on top — not within.
The Cadogan Estate covers a significant portion of the southern boundary between Kensington and Chelsea. If your property falls within it, a Licence to Alter is required before structural works begin — separate from RBKC planning permission. Typical review period: four to six weeks from a complete submission. The licence covers both structural and decorative changes. Completing works without it risks forfeiture of the lease.
RBKC enforces strict working hours: 08:00–18:00 Monday to Friday, 08:00–13:00 Saturday. No Sunday or bank holiday working. Construction Traffic Management Plans are mandatory for basement projects. Skip permits carry borough-specific charges and maximum placement periods. Every contractor vehicle on site is subject to Congestion Charge and ULEZ daily charges for the duration of the programme.
Conservation area and basement policy compliance adds 15–25% to base costs versus boroughs with fewer restrictions. Professional fees run higher due to the listed building and conservation area application load. A 200m² Victorian terrace in Kensington budgets at £600k–£1m for a full renovation at premium specification. Basement conversions with excavation, underpinning, and tanking add £3,500–5,500/m² on top of above-ground works. Pre-construction planning adds 10–16 weeks before site start. The single biggest cost variable is listed building status — a listed property in Kensington can cost 20–30% more than an unlisted one on the same street, because every material choice and every method requires conservation officer sign-off.
The pre-construction period — planning, party wall, structural investigation, CTMP approval — routinely takes longer than the construction itself. A basement that takes five months to build typically takes nine to twelve months to reach site start.
Same planning authority as Kensington, same basement SPD, same conservation area framework. But Chelsea’s street-level constraints differ. Conservation area density runs higher still in the core SW3 streets. Pre-construction periods routinely exceed construction duration. All external alterations — rear extensions, roof changes, window replacements — require conservation area consent. The 2015 basement policy applies identically to Kensington: single-storey, beneath existing footprint, full planning application. Chelsea’s particular challenge is the terrace housing stock: narrow sites, shared walls on both sides, and rear gardens that back onto neighbours at close proximity. Rear extension applications draw more objections here than almost anywhere else in the borough.
The Cadogan Estate is the dominant landowner in Chelsea. Most residential leases require written estate consent before any works begin. Cadogan’s review covers scope, specification, appointed contractor, and programme. Approval takes four to eight weeks. Completing works without consent is a lease breach regardless of RBKC planning approval. The estate’s appointed surveyors conduct their own site inspections during and after construction.
Many Chelsea properties sit within three metres of a public Victorian sewer. Construction within that boundary requires a Thames Water build-over agreement — a separate statutory process, independent of planning permission. Discovery during excavation halts the project until the agreement is in place. Party wall agreements on terrace streets involve multiple adjoining owners — three to five notices on a mid-terrace property is standard. Each notice carries its own two-month response window.
The combined impact of Cadogan estate consent, Thames Water build-over risk, and multi-party wall agreements pushes pre-construction costs higher than the headline £/m² suggests. Programme durations for basement projects run long — the gap between breaking ground and completion is smaller than the gap between instruction and breaking ground. Professional fees for a Chelsea basement typically run 10–13% of construction cost. The estate’s appointed surveyor charges are an additional cost borne by the leaseholder, not the contractor. Factor the full consent chain into the budget from the start — not as a contingency, but as a fixed line item.
A Mayfair renovation can require three separate consents running concurrently: Westminster planning permission, Listed Building Consent, and written approval from the Grosvenor Estate — even if you own the freehold.
Conservation area coverage across Mayfair is effectively 100% — the entire neighbourhood sits within the Mayfair Conservation Area. Listed building concentration is among the highest in London. Any external alteration requires planning permission. Internal structural works to listed buildings require Listed Building Consent. Westminster’s planning committee is notably conservative on material changes to historic facades. Expect longer determination periods and more conditions attached to approvals than in RBKC. Basement policy in Westminster is less restrictive than RBKC’s — multi-storey basements are possible in principle — but the listed building status of most Mayfair properties means the structural impact assessment is more demanding. Applications are assessed by both the planning team and the conservation officer, who may have conflicting priorities.
The Grosvenor Estate manages the majority of Mayfair’s residential property. Estate consent is required for all works — structural, mechanical, and decorative — even if you own the freehold. Grosvenor appoints its own surveyor to review proposals. Three concurrent consents are the norm: Westminster planning, Listed Building Consent, and Grosvenor estate approval. Each has its own timeline and its own consultees. None waits for the others. Mapping all three at the start is not optional.
Every contractor vehicle on a Mayfair site is subject to Congestion Charge and ULEZ daily charges for the duration of the project. On an eight-month programme, that is a five-figure cost in preliminaries alone. Delivery windows are restricted on major streets. Westminster’s skip permit costs and placement restrictions are the most expensive in Central London. On-street parking suspension for construction vehicles requires a council permit with a minimum 10-day notice period and carries daily charges.
Mayfair carries the highest renovation costs of the five boroughs. The triple consent layer, listed building compliance costs, and Westminster’s logistics charges all compound. Professional fees run 12–15% of construction cost versus 8–10% in less restricted boroughs. A 150m² lateral conversion in Mayfair budgets at £525k–£900k before professional fees. Ask your contractor to show Congestion Charge and ULEZ as named line items in the preliminaries — not as a contingency, and not as a variation later. On an eight-month programme with daily van and lorry movements, transport charges alone can exceed £15,000. If your contractor does not itemise these, they are either absorbing them in the margin or planning to recover them as a variation.
Painting the stucco facade a different shade requires a planning application. So does replacing railings, altering gates, or adding any structure visible from the highway. The Article 4 Direction leaves nothing to permitted development.
Same planning authority as Mayfair. Belgravia’s stucco terraces are almost entirely within the Belgravia Conservation Area, and most are Grade II listed. The Article 4 Direction removes permitted development rights for all external alterations. Internal works to listed properties need Listed Building Consent. Westminster applies the same conservative approach to material approval as in Mayfair, but Belgravia’s homogeneous terrace architecture means any deviation from the existing palette is more visible and more likely to draw objections from the conservation officer. The uniformity is the point: Belgravia’s terraces were designed as unified compositions, not individual houses. Planning applications that break the rhythm — different window proportions, non-matching stucco colour, altered rooflines — face a higher refusal rate.
The Grosvenor Estate dominates Belgravia. Same consent regime as Mayfair: estate approval required for structural, mechanical, and decorative works. Belgravia leaseholders face an additional layer — many leases include specific clauses on stucco maintenance, window joinery, and ironwork specification that go beyond planning requirements. The estate enforces these independently of the council. Non-compliance is a lease breach, regardless of planning consent. Grosvenor’s surveyors inspect during construction and again before sign-off. If the executed work deviates from the approved specification — even if it meets building regulations — the estate can require remedial works at the leaseholder’s expense.
A significant proportion of Belgravia’s adjoining properties are occupied by embassies or held by international owners with absentee management. Serving party wall notices in these circumstances takes longer — four to six weeks for a response is standard, and tracking down the correct respondent adds time. Security-sensitive neighbours may impose additional construction constraints not covered by the statutory framework. Factor party wall timelines into the programme from the outset — the statutory minimums rarely apply in Belgravia.
The listed building overlay on virtually every property pushes specification costs upward. Heritage-compliant window joinery, conservation-grade stucco repairs, and approved ironwork all carry premium rates. Grosvenor’s lease-specific requirements add scope that wouldn’t exist in a freehold property — the estate may require specific suppliers, approved materials, and post-completion inspections that add both cost and programme. The cost of getting it wrong is lease forfeiture, which means the margin for error is zero. A typical 250m² Belgravia terrace renovation with basement, at premium specification, budgets at £800k–£1.4m. The lower end assumes an unlisted property with cooperative neighbours and a clean party wall process. The upper end assumes Grade II listed, embassy neighbours, and a Grosvenor lease with prescriptive clauses.
Two estate consent regimes operate side by side. The Howard de Walden Estate and the Portman Estate together cover the majority of residential streets — and neither recognises the other’s approval.
Conservation area coverage in central Marylebone is extensive, though not as comprehensive as Mayfair or Belgravia. The neighbourhood contains a mix of listed and unlisted residential stock — mansion blocks, mews houses, and Georgian terraces coexist within a few streets. Westminster’s planning rules apply uniformly, but the variety of property types means the planning path varies more here than in Belgravia’s homogeneous terraces. Unlisted properties in non-conservation streets may qualify for permitted development — a meaningful cost and programme advantage.
Two estate consent regimes operate concurrently. The Howard de Walden Estate and the Portman Estate together cover the majority of residential streets. Both require a Licence to Alter before structural works begin, separate from Westminster planning permission. Review periods: four to eight weeks from a complete submission. The estates appoint their own surveyors and conduct independent site inspections. Properties near the estate boundary may fall under both jurisdictions — neither estate recognises the other’s approval. The Licence to Alter process covers not only structural changes but also mechanical and electrical layouts, kitchen and bathroom specifications, and in some cases, decorative finishes. Submit a complete proposal the first time — incomplete applications reset the clock.
The Tyburn — a lost river running beneath Marylebone Lane — creates groundwater conditions in basement excavations that no desktop survey will predict. Trial pits and a geotechnical engineer on site before the contract is signed are the only way to price below-ground work accurately. Mansion block renovations carry additional logistics: communal access agreements, restricted lift use for material transport, and building management company approval for works schedules. Mews house access is limited by lane width — standard delivery vehicles may not fit.
Marylebone’s cost range is broad because the property stock is diverse. Mansion block renovations carry lower structural costs but higher logistics costs due to access constraints and building management requirements. Mews house conversions sit at the upper end due to limited access and party wall complexity — scaffolding alone can add £15,000–30,000 in a narrow lane. Basement conversion costs vary more here than in any other borough — the groundwater risk means the gap between low and high estimate is wider. A geotech report before contract is the only way to narrow it. Georgian terrace renovations in conservation areas carry comparable costs to Belgravia — but without the Grosvenor Estate layer, pre-construction timelines are shorter and professional fees are lower. For properties outside conservation areas with no estate lease, Marylebone offers the most cost-effective renovation of the five boroughs.
No. Every borough has a planning authority, an estate management layer, and a logistics profile. We built our pricing, our programme templates, and our supply chain around these five. A project outside them would mean starting from scratch on all three. We would rather do five areas properly than fifteen badly.
Yes. Same property, same scope, different borough — different number. Conservation area density, basement policy, working hour restrictions, skip permit costs, and estate licence requirements all vary. Mayfair runs 20–40% higher than Marylebone on a comparable full renovation. The calculator accounts for borough. The PCSA prices for it line by line.
No. That is what the first conversation is for. We identify the planning authority, conservation area status, estate management requirements, and logistical constraints for your property. You do not need to research any of this before making contact. Pick your area above, or go straight to the form.
Yes. Four of our five boroughs have conservation area coverage above 70%. Most of our projects sit within one. The additional requirements — material approval, conservation officer consultation, extended planning timelines — are built into our standard programme and pricing. They are not surprises. They are line items.
It depends on the borough and the scope. Internal-only works with no listed building status and no estate lease: four to six weeks. Full renovation with basement, listed building consent, estate approval, and multi-party wall agreements: twelve to twenty weeks before a contractor sets foot on site. We map the full consent chain in the first conversation so the programme reflects the actual timeline, not a hopeful one.
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