Basement works in HA4
HA4 covers Ruislip & Eastcote. For basement works, the route depends on the exact property: conservation areas, Article 4 directions, listed status, tenure and the scheme details all change the answer. Use this district guide as local context, then run the address check before relying on permitted development or any consent assumption.
HA4 covers Ruislip and Eastcote — the Ruislip Village, Eastcote Village and Eastcote Park Estate conservation areas, with Ruislip Woods beyond. Inside the conservation areas a full application is the norm; the surrounding Metro-land stock keeps PD rights, subject to the borough's Article 4 directions.
First checks for basement
Service-specific- Planning permission and the borough's basement policy
- Party wall agreements with every affected neighbour
- Ground/water conditions and a Basement Impact Assessment
District pages are not point-level checks. They do not confirm whether a specific property is listed, inside a conservation area, or subject to an Article 4 direction.
Local planning context · Hillingdon
Real · planning.data.gov.ukHillingdon has 31 conservation areas and 4 Article 4 areas in the official dataset. HA4 is too broad to say which apply to your property; the address check tests the point against available geometry.
Read the borough-wide context on the Hillingdon planning guide.
What changes the route?
| Where constraints apply | Expect a full planning application with a Basement Impact Assessment — this is the highest-risk domestic project. |
| Where no designation is found | Basements normally need full planning permission in London regardless — budget for a Basement Impact Assessment. |
Approvals and who deals with them
| What you may need | Likelihood | Who usually deals with it |
|---|---|---|
| Planning permission New or extended basements normally need full planning permission in London; many boroughs apply a specific basement policy. | Required | Planning consultant / architect |
| Basement Impact Assessment / method statement Most London councils require a BIA covering structure, ground movement, hydrology and construction method. | Required | Specialist basement engineer |
| Building Regulations approval Required — structure, waterproofing (tanking), drainage, ventilation and fire. | Required | Building control + your builder |
| Party Wall etc. Act 1996 notice Deep excavation adjacent to neighbours engages the Act on every shared boundary — expect surveyors and awards. | Required | Party wall surveyor |
| Specialist basement structural engineer Underpinning and retaining design needs a specialist structural engineer throughout. | Required | Specialist basement engineer |
| Drainage / SuDS / flood-risk information Pumped drainage, sustainable drainage and flood resilience are commonly required. | Verify | Drainage engineer + water authority |
| Listed building consent We do NOT check listed status. If the property is listed, consent is needed for works affecting its character — confirm on the National Heritage List for England. | Verify | Heritage adviser / conservation officer |
Cost context
| Cost per m² — lower (straightforward) | £6,000 / m² |
| Cost per m² — typical | £8,500 / m² |
| Cost per m² — higher (complex / conservation spec) | £12,000 / m² |
| Typical project (35–50 m²) | £210,000 – £600,000 |
Basements carry the widest cost uncertainty of any project — ground conditions can move budgets six figures. Never commit on a single quote without a ground investigation. VAT excluded.
Watch-outs in HA4
- Underestimating party-wall cost and time — awards on multiple boundaries can run to months and five figures before excavation.
- Ground-water and made-ground conditions driving waterproofing and pumping cost.
- Borough basement policy capping depth, footprint or garden coverage.
- Neighbour objections and monitoring conditions extending the programme.
Next steps
- Commission a specialist basement structural engineer and (where required) a Basement Impact Assessment author.
- Establish the borough's basement policy limits before designing.
- Serve Party Wall notices early to every affected neighbour and budget for awards.
- Submit a full planning application with the BIA and method statement.
Related guides
The biggest space gain in London — bought at the steepest price.
Read the guide →Almost every London extension, loft and basement engages this Act. Here's how it actually works.
Read the guide →More services in HA4
First check: Freeholder consent / Licence to Alter — read your lease's alterations clause
Service guide →First check: A structural engineer's check on whether the wall is load-bearing
Service guide →First check: Whether it's permitted development or needs a planning application
Service guide →First check: Whether the dormer needs planning permission
Service guide →First check: The intended use (office/gym vs sleeping) — it changes everything
Service guide →First check: The property's planning history and any enforcement
Service guide →First check: Whether the building is listed, and at what grade
Service guide →Planning Permission Checker provides planning and cost intelligence for early feasibility only. It is not legal, planning, valuation, architectural, structural, or surveying advice. All estimates are indicative and must be verified by qualified professionals before purchase, design, planning submission, or construction.
Cost estimates are indicative only — not a quotation. Final price depends on survey, specification, structure, access, party wall matters, VAT, professional fees, and contractor availability.
Planning outcomes are not guaranteed. Local planning authorities make final decisions.