Marylebone runs two estate consent regimes at once. The Howard de Walden Estate and the Portman Estate together cover the majority of residential streets, and a property near the boundary can fall under both. Neither recognises the other’s approval, which makes the first question in Marylebone a question about jurisdiction rather than about the building.
Conservation area coverage in central Marylebone is extensive, though not as comprehensive as Mayfair or Belgravia. The stock is mixed: mansion blocks, mews houses and Georgian terraces coexisting 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. Determination periods vary by application type.
One consequence is worth stating plainly, because it is the only case of it in the five. Unlisted properties on non-conservation streets may still qualify for permitted development. That is a real cost and programme advantage, and it exists nowhere else in this list.
Both estates require a Licence to Alter before structural works begin, separate from Westminster planning permission. Review periods run four to eight weeks from a complete submission, and each estate appoints its own surveyors and conducts independent site inspections.
The licence covers more than structure. Mechanical and electrical layouts, kitchen and bathroom specifications and in some cases decorative finishes all fall inside it. Submit a complete proposal the first time, because an incomplete application resets the clock.
Properties near the estate boundary may fall under both jurisdictions at once, and neither estate treats the other’s approval as sufficient. Establishing which estate holds your street, or whether both do, is the first thing to settle.
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 here.
Mansion block renovations carry their own logistics: communal access agreements, restricted lift use for moving materials, and building management company approval for the works schedule. Mews access is limited by lane width, and standard delivery vehicles may not fit.
The cost range here is broad because the stock is diverse. Mansion blocks carry lower structural costs and higher logistics costs, because of access constraints and building management requirements. Mews conversions sit at the upper end, on limited access and party wall complexity. Scaffolding alone can add £15,000 to £30,000 in a narrow lane.
Basement costs vary more here than in any other borough, because the groundwater risk widens the gap between the low and high estimate. A geotechnical report before contract is the only thing that narrows it.
Georgian terrace renovations in conservation areas carry comparable costs to Belgravia. Without the Grosvenor layer, pre-construction timelines are shorter and professional fees lower. For a property outside a conservation area with no estate lease, Marylebone is the most cost-effective renovation of the five.
Typical programme 18 to 30 weeks. Pre-construction 8 to 16 weeks.
Both estates publish their holdings, and the lease will say. It matters before design starts, because a property near the boundary can fall under both and each runs its own review. Settling jurisdiction first avoids submitting to the wrong one.
It affects the pricing of it, whether or not you hit water. Groundwater conditions near the lost river are not predictable from a desktop survey, so the honest position before trial pits is a wide range. A geotechnical report before contract is what turns that range into a number.
Not in practice. Communal access agreements, lift restrictions for material transport and management company approval of the works schedule all sit outside both planning and estate consent. They are a separate permission chain and they set the programme.
Potentially quite a lot. Permitted development may be available, which removes an application from the front of the programme. It is the only borough of the five where that is a realistic starting position, and it depends on the address rather than the borough.
Usually yes. The licence covers mechanical and electrical layouts, kitchen and bathroom specifications, and in some cases decorative finishes, so internal-only work is frequently inside it. The trigger is the lease, not whether anything is visible from the street.
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