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Deep-dive · Basement Conversions

The complete Basement Conversions guide

Everything we know about basement conversions in London, in one place.

Fast facts

Service
Basement Conversions
Typical duration
12–14 weeks
Approval rate
98% first time
Coverage
33 London boroughs + M25 belt
MCIAT chartered
Yes

London period house exterior with architectural character — basement conversions in London

What's covered

This page is the deep-dive index for Basement Conversions. Read it linearly or jump to the section you need.

1. Why people choose basement conversions

Three common drivers in London: family-growth space pressure, value uplift on Victorian/Edwardian stock, and rising rent making moving up the ladder uneconomic. Basement Conversions captures all three.

2. The planning route

For most London homes that aren't flats, listed or in conservation areas, basement conversions qualifies under Permitted Development. The basement conversion drawings test: under volume threshold, materials match, eaves setback. Where Article 4 applies, the LDC route gives certainty before building. Where conservation rules apply, full planning is required.

3. Building regulations

Part L (thermal), Part B (fire), Part M (access), Part K (stairs/falls), Part E (acoustic), Part F (ventilation). Each governs a different aspect of the basement conversion drawings. Sign-off via LABC or Approved Inspector.

4. Pricing in detail

Council fees: £103-£206. Building regs fees: £400-£900. Structural engineer: £800-£1,500. Build cost: separate quote from a contractor.

5. Common pitfalls

Wrong PD assumption (Article 4 area). Material non-match in conservation areas. Insufficient Heritage Statement detail on listed property. Missing Party Wall notice triggering legal injunction. We solve all of these as standard.

The complete Basement Conversions guide in London — the exterior of London house before works
The exterior of a london house before works — the complete basement conversions guide in London.
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An architectural technologist checking a printed set of house drawings, marking a proposed elevation in red — the complete basement conversions guide in London
Every set is checked line by line against the validation checklist before it leaves the office.

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council-ready drawing review · All 33 London boroughs