That does not mean every alteration needs planning permission: the answer depends on the particular work and whether it amounts to development needing permission. [1] [2]
Start with the legal property, not its appearance
A flat can occupy part of a building that looks like a terraced house. Having its own entrance or garden does not make the flat eligible for the householder extension rules. Establish whether the premises are a house, a flat or a maisonette before using an online size-limit checklist. [1] [3]
An extension to a ground-floor flat requires a planning application. The householder allowances commonly discussed for neighbouring houses should not be used to decide its permissible depth or height. [3]
Some work may not need a planning application
Replacing a flat's windows with genuinely identical windows will not normally require planning permission. A change in appearance or size may produce a different answer. Internal secondary glazing will also normally be outside planning control, but listed building consent is a separate question. [2]
There can also be permitted development rights under provisions other than the householder rules. For example, Waltham Forest's guidance explains that the national change-of-use route from an ordinary dwelling to a small HMO can involve a house or flat, but its borough-wide Article 4 direction removes that route locally. This is not permission to extend the building. [4]
Check restrictions separately
An Article 4 direction withdraws only the rights it specifies. It is not a blanket ban on alterations. Read the actual direction and map rather than assuming that every property in a conservation area has the same controls. Existing planning conditions can also remove otherwise available rights. [1]
Planning permission does not override the lease. The lease may require written consent, prohibit an alteration or exclude the structure being changed from the property you own. An owner's share in the freehold does not make these questions disappear. [5] [6]
Building regulations are another separate check. Alterations involving structure, fire safety, services or controlled fittings may need approval even where there is no planning application. A higher-risk residential building may have a different building-control route. [7] [8]
A practical checking sequence
- Gather the lease plan, existing layout and relevant planning decisions.
- Describe the work precisely: extension, altered opening, replacement fitting or change of use.
- Check the applicable national planning rule and the council's restrictions.
- Resolve landlord consent and building-control requirements before committing to installation. [5] [1] [7]
Keep these answers separate in the project record. “No planning application needed” is not the same conclusion as “no permission or technical approval needed”. [7] [5]