Renovating a London Flat: Planning, Leasehold Consent, Costs and What to Watch Out For

Before any other action, read your lease. The vast majority of London flat leases contain clauses that restrict alterations. Typical lease clauses require:

Landlord's consent: most leases require the leaseholder to obtain written consent from the freeholder (or their managing agent) before carrying out structural alterations, internal layout changes, or any works that affect the structure, communal services, or building fabric. Failure to obtain consent is a breach of the lease, which can result in the freeholder applying for a forfeiture order (termination of the lease) in extreme cases, and which must be disclosed on sale.

Notification: even where formal consent is not required for minor works (such as redecoration), many leases require the leaseholder to notify the freeholder in writing before any works begin.

Approved contractors: some leases require works to be carried out only by approved or adequately insured contractors. Check whether your lease has this requirement.

Access for inspection: freeholders typically reserve the right to inspect works in progress and at completion.

Making good: the leaseholder is responsible for making good any damage caused during works and for ensuring the property is returned to its pre-works condition if works are not approved.

Common specific restrictions in London flat leases:

• Replacing carpets with hard flooring (due to noise impact on neighbours below — often requires sound insulation to a specified standard)
• Removing or altering internal walls (structural concerns)
• Changing windows or external doors (which are usually part of the building fabric owned by the freeholder)
• Alterations to heating or hot water systems (which may affect common services)
• Any works to the bathroom or kitchen

For any structural or significant alteration, the standard route to freeholder consent is the Licence to Alter (also called a Licence for Alterations). This is a formal legal document signed by the freeholder, the leaseholder, and (if there is a mortgage) sometimes the mortgagee, recording the consent and any conditions attached to it.

The Licence to Alter process typically involves:

1. Submitting your proposed works to the freeholder (usually through their solicitor or managing agent) with drawings, specifications, and contractor details
2. The freeholder (or their advisors) reviewing the proposal
3. Negotiation of any conditions (e.g., sound insulation specification for new hard floors, requirement for approved contractors)
4. Execution of the Licence by all parties

Timescale: allow 4 to 12 weeks for a Licence to Alter, depending on the freeholder's responsiveness and the complexity of the works. This is a critical-path item — do not commit to a contractor start date until consent is confirmed.

Cost: freeholders typically charge for the cost of reviewing the application (solicitor and surveyor fees), which are usually passed to the leaseholder. Costs range from £500 to £3,000+ for a standard Licence to Alter.

Internal works in a flat almost never require planning permission — internal alterations do not constitute development under the Town and Country Planning Act 1990. However, planning permission IS required for:

• Any external alteration (windows, external doors, external cladding changes)
• Loft spaces above a flat (if they form part of the demise and the flat is in a building where the loft can be converted)
• Any extension to the building (which would also require freeholder consent and the involvement of all leaseholders)

Conservation area considerations: in conservation areas, external alterations (even painting) may require Householder Prior Approval or planning permission.

Building Regulations apply to structural works, electrical alterations, plumbing alterations, and changes to thermal elements in a flat, including:

• Structural wall removal or alteration (Part A)
• New or altered electrical installation (Part P — must be certified by a Part P-registered electrician or notified to Building Control)
• Plumbing and drainage alterations (Part H and G)
• Replacement windows or doors (Part L, Part K for safety glazing)
• Heating system alterations (Part J)
• New bathroom (Part F ventilation, Part G sanitation, Part H drainage)

Do not assume an internal flat renovation is exempt from Building Regulations — it rarely is, except for basic redecoration.

Removing or altering internal walls in a flat is structurally more complex than in a house:

• The floor above is someone else's flat — any structural work to the wall must not compromise the structure supporting that flat
• Services (water, waste, electrics) may run through or alongside the wall
• The structural system of a post-war block may use load-bearing cross-walls, making what appears to be a partition wall actually a structural element
• Party walls between flats require structural engineering sign-off even where not traditionally "party wall" in the legal sense

A structural engineer must assess any wall before it is removed or altered.

Noise between flats (airborne noise from voices and TV; impact noise from footsteps) is one of the most common sources of neighbour disputes in London apartment buildings. Building Regulations Approved Document E (Resistance to the Passage of Sound) sets minimum sound insulation standards for new buildings and conversions — but existing flat floors may not meet these standards.

Replacing floor finishes: installing hard flooring (timber, tiles, stone) over an existing floor system that was designed for carpet significantly increases impact noise transmission to the flat below. Many leases specifically prohibit hard flooring without the installation of impact sound insulation. Floating floor systems with acoustic underlay (e.g., 5-10mm acoustic foam, acoustic rubber matting, or specialist floating floor assemblies) reduce impact noise transmission.

• Studio/1-bedroom flat (35–50m²) — cosmetic renovation (new kitchen, bathroom, flooring, decoration): £18,000 to £35,000
• 2-bedroom flat (55–75m²) — full renovation including kitchen, bathroom, flooring, electrics, plumbing update: £35,000 to £65,000
• 3+ bedroom flat (80–120m²) — comprehensive renovation with structural alterations: £65,000 to £120,000+
• Licence to Alter legal and surveyor fees: £800 to £3,000
• Sound insulation upgrade (acoustic floating floor, ceiling system): £4,000 to £12,000 depending on area
• Structural engineer (if walls to be removed): £600 to £1,500