Local plan
Hillingdon’s adopted borough framework comprises Local Plan Part 1, adopted on 8 November 2012, and Part 2, adopted on 16 January 2020, which replaced the saved Unitary Development Plan policies. [1][2]
Home-project references include DMHD1–3 for extensions, outbuildings and basements, and DMH4–6 for residential conversions, HMOs and garden or backland development. [3]
Check the separate Site Allocations and Designations document and adopted Policies Map for the site, rather than treating the general design policies as the whole planning assessment. [4][5]
The replacement is still emerging: timetable version 2, published 29 September 2026, targets a content consultation from 8 April to 27 May 2027 and consideration of adoption on 22 January 2029, not an already-approved replacement plan. [6]
Council guidanceHouseholder design guide
Use Appendix A of the adopted Development Management Policies, which contains Hillingdon’s householder guidance and DMHD1–3. [3]
DMHD1 addresses rear, side, front and roof extensions, including their effect on neighbours. [3]
Its rear-extension categories for terraced and semi-detached houses overlap at a plot width of exactly 5 m, so obtain clarification before using either depth limit for that boundary case. [3]
These are planning-assessment policies, not a grant of permitted development: check the separate Article 4 restrictions, particularly the borough-wide control on larger rear extensions, before choosing the application route. [3][12]
Council guidanceValidation list
The council's current application page links to its February 2024 Local Planning Validation Checklist, with a separate householder checklist at printed page 14. Confirm that the linked list and any subsequent updates cover your application type. [8][9]
For householders it lists the application documents and drawings, alongside relevant local evidence such as basement assessments, heritage information, flood-risk information, parking details and tree information, rather than requiring every report for every project. [9]
The document still quotes a historic Mayoral CIL rate, so use the current CIL sources below for charges, not the checklist’s monetary example. [9][25]
Confirm the applicable submission requirements before commissioning reports: NPPF DM2 requires additional local information requirements to have development-plan support and to be proportionate to the proposal, rather than applied identically to all applications. [10]
Council guidanceArticle 4 directions
Two important borough-wide directions affect homes: the C3-to-C4 HMO direction took effect on 11 December 2025 and was confirmed on 21 May 2026, so its coverage is no longer limited to the earlier Brunel and Uxbridge South areas. [11][40]
The separate confirmed rear-extension direction, effective 22 September 2014, removes the relevant permitted development right for a single-storey enlargement extending more than 4 m beyond the original rear wall; do not assume the usual larger-extension prior-approval route remains available for that work. [12][41]
Class MA commercial-to-residential controls apply to selected mapped locations, with their coverage reduced by modifications effective 27 March 2024, not automatically to every building in an employment area or town centre. [13][14]
Separate Part 20 Classes AA, AB and ZA directions control specified rooftop or demolition-and-rebuilding routes in mapped locations, also modified on 27 March 2024; check the direction’s own boundary, not merely the underlying Local Plan designation. [15][16][17]
Council guidanceConservation areas
Hillingdon lists 31 conservation areas, with an area-by-area directory linking to boundary maps and available appraisals or management guidance. [18][19]
Use the particular area’s map to locate the property, such as the council-linked Ruislip Village boundary map, rather than assuming a whole neighbourhood shares the designation. [19][22]
The council asks conservation-area planning applications to include a heritage statement and says available appraisals and management plans should inform the design alongside national and local policies. [20]
Its general heritage map is expressly indicative rather than a definitive detailed record; unresolved boundary or document questions can be sent to heritageconservation@hillingdon.gov.uk. [21]
Council guidanceBasement policy
DMHD3, supported by paragraphs A1.35–A1.43, governs basements. [3]
It excludes habitable basement uses in flood-prone areas and basement schemes in listed buildings, but its conservation-area restriction depends on harm to the area’s character. [3]
The supporting text rejects front or side lightwells and subterranean schemes extending the full length or width of a property, and requires applicants to fund independent structural-report assessment. [3]
The validation checklist separately requests a technical basement assessment for new or extended basements covering drainage, flooding, groundwater and structural stability; agree its scope with the council in light of the scheme and the current information-requirements policy. [9][10]
Council guidanceCIL rates
Hillingdon’s 2026 annual summary prints £160.43/m² for Class C3 residential development, but that figure does not match the calculation printed beside it; obtain confirmation from cil@hillingdon.gov.uk before costing the borough component. [23][24]
The separate Mayoral CIL2 Band 2 rate is £72.73/m² for permissions granted in 2026, according to the GLA’s annual summary. [25]
The borough schedule has applied since 1 August 2014, and the annual tables already include indexation; these are rates, not a project liability, which the council establishes using the submitted development information. [23][24][25]
Do not deduct a proposed temporary London borough-CIL discount unless the final implementing provisions establish that it applies to the development. [33]
Council guidancePre-application advice
The council offers free verbal duty-planner advice for householder and other small proposals, requested through planning@hillingdon.gov.uk; written advice is a separate service. [26][28]
The guidance headed 1 April 2026 lists £110 including VAT for general follow-up written householder advice after the duty consultation, and £504 including VAT for full Category F advice, including one new dwelling and specified extension or alteration proposals. [26][27]
Category F is written advice without a standard meeting or site visit, while Category E for 2–4 homes is £3,648 including VAT; confirm the category rather than assuming all small residential proposals cost the same. [26][27]
Submit formal requests with the relevant documents to applicationsprocessingteam@hillingdon.gov.uk; advice is not planning permission, specialist reviews can cost extra, and the published response targets are not guarantees. [26][29]
Council guidanceBuilding control
Contact council building control at buildingcontrol@hillingdon.gov.uk, or use the council’s building-control application and inspection pages. [30][31][32]
Its 2026/27 tariff applies to applications deposited from 1 April 2026 until further notice and identifies the postal address as Building Control, Residents Services, 3N/01, Civic Centre, High Street, Uxbridge, UB8 1UW. [30]
For illustration, the published standard charge for a domestic extension under 40 m² is £1,122 including VAT, with inspection included in the full-plans charge; multiple types of work can attract separate charges, so obtain a project-specific confirmation. [30]
Request inspections through the online booking service, but wait for confirmation because a requested day, or morning or afternoon preference, is not guaranteed. [32]
Council guidance