Basement Conversion Drawings in Eltham SE9
Fixed-fee, MCIAT-chartered basement conversion drawings for Eltham (SE9) homeowners — Royal Borough of Greenwich validation and local constraints handled from the start.
Eltham (SE9) sits in the Royal Borough of Greenwich and is best known for the Progress Estate at Well Hall — a 1915 Arts-and-Crafts garden suburb that inspired much interwar housing and has been a conservation area since 1971. An Article 4 direction covers the estate, so on those streets even small external changes need consent, and rear and loft projects have to be handled with real care for the original detailing.
Away from the estate, much of Eltham is consistent interwar semi-detached and terraced housing where side-return, rear and loft projects are the staple. The district also carries the setting of Eltham Palace and its listed gardens. We check where an Eltham property sits relative to the Progress Estate Article 4 area and the palace setting before recommending a permitted-development or full-application route under Greenwich's guidance.
Planning in Eltham (SE9): what to know before you apply
Eltham's Progress Estate at Well Hall carries a conservation-area designation and an Article 4 direction (1973), so permitted-development rights are removed across the estate and external changes need planning permission. Elsewhere in SE9 many interwar houses retain PD rights for rear and loft work, but the consistent frontages and the setting of Grade I listed Eltham Palace mean elevation and roof changes are assessed closely. We confirm which controls apply to a specific address before drawing.
Typical Eltham housing stock
The 1915 Arts-and-Crafts cottages and greens of the Progress Estate around Well Hall Road, interwar semi-detached and terraced housing across much of Eltham, and later post-war housing toward Mottingham and New Eltham.
Streets we regularly draw for in Eltham
Well Hall Road · Court Road · Eltham High Street · Ross Way
What SE9 is actually built of
Measured from 511 classified residential buildings in SE9, not from a description of the area.
Eltham SE9 housing mix
Residential building form across the SE9 postcode district, from 511 classified buildings.
| Attached on more than one side | 39% |
|---|---|
| Attached on one side | 57% |
| Detached | 4% |
| Median building footprint | 62 m² |
| Addresses per buildingAbove about 2 means flats and maisonettes dominate | 1.22 |
| Buildings classified | 511 |
Source: Ordnance Survey National Geographic Database (derived statistics). Contains OS data © Crown copyright and database right 2026. Contains Royal Mail data © Royal Mail copyright and database right 2026. Extracted 2026-08-17.
Basement Conversion Drawings for Eltham (SE9) homes: the package and the process
A basement package is led by its section. It has to show the existing structure, the proposed floor level, retained or underpinned walls, the tanking system, and how the finished room achieves head height without undermining what sits above. Structural design and architectural design are drawn together because here they are the same decision.
Habitable basement rooms also need light, ventilation and escape. The drawings set out lightwells and their guarding, mechanical ventilation where natural is not achievable, and an escape route that Building Control will accept — usually a protected stair, sometimes an external route out of the lightwell.
What sits below the house decides the route. An existing cellar under a Victorian terrace is a conversion with a known volume, while a house with no cellar is a dig-out with underpinning, structural design and a very different drawing set — and the two are rarely interchangeable.
Do I need planning permission for a basement conversion in London?
An internal conversion of an existing cellar — new floor, insulation, a habitable layout — often does not need planning permission, because the works sit entirely within the existing structure and do not change its external appearance. Digging out a new basement, lowering an existing floor to gain headroom, or enlarging the footprint under a garden usually does, particularly where excavation extends beyond the existing building line. Any external alteration needed to serve the basement — a front light well, a sunken external staircase, or altering the pavement or front garden — is also likely to need planning permission in its own right, even when the basement works themselves would not. In a conservation area, a front light well tends to draw closer scrutiny than the same feature elsewhere, since it changes the street-facing elevation and the pavement it sits within — one more reason we assess the whole scheme, not just the room below ground, before recommending a route.
Cellar conversion or new dig-out — which route fits your property?
The two starting points lead to very different drawing sets. A cellar conversion works with a void that already exists: the drawings focus on damp-proofing, insulation, headroom, natural or borrowed light, means of escape and a compliant layout, coordinated with building regulations rather than planning.
A new dig-out or floor-lowering project starts from a structural decision — how the existing foundations will be underpinned to allow excavation beneath them — and the drawings and structural calculations are produced together from the outset, since the sequence of underpinning, temporary works and waterproofing has to be engineered before a builder can safely start.
What structural design does underpinning a basement need?
Lowering a floor or digging a new basement beneath an existing house means underpinning its foundations in sequenced sections, so the building above stays supported throughout. We produce the structural drawings and calculations for the underpinning sequence, any new steel beams or retaining walls, and the interaction with neighbouring foundations, in-house as part of the same package — so your structural engineer sign-off and your architectural drawings are never out of step with each other.
The sequencing matters as much as the sizing: underpinning is dug and cast in short, alternating sections so the existing wall is never left unsupported over any significant length, and the drawings set out the order those sections are worked in alongside the retaining and waterproofing detail. Getting that sequence wrong is one of the most common causes of cracking and delay on a basement project, which is why we treat it as a design decision rather than something left for the contractor to work out on site.
| Route | Typical scope | Planning position | Fee from |
|---|---|---|---|
| Existing cellar conversion | Fit-out of an existing void, no excavation | Usually building regulations only | £2,400 |
| Floor lowering / partial dig-out | Increases headroom within the existing footprint | Often needs planning permission | £3,200 |
| New-build basement or light well extension | New basement area beyond the existing footprint | Full planning plus Party Wall Act | £3,850 |
Basement Conversion Drawings in Eltham SE9 — FAQs
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How does the Maritime Greenwich World Heritage Site affect my project?+
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