Extending or Renovating a Leasehold Flat in London: What You Need to Know

Millions of Londoners own leasehold flats — and millions of those owners want to renovate, extend, or improve their properties at some point. But the legal framework governing leasehold properties adds a significant layer of complexity compared to freehold houses. This guide explains what you need to do, who you need permission from, and how to navigate the process successfully.

The Key Difference: You Don’t Own the Building

As a leaseholder, you own a long lease on your flat (typically 99, 125, or 999 years) but you do not own the building itself or the land it sits on. The freeholder (or their managing agent) owns the fabric of the building: the external walls, the roof, the structure, the common parts. This matters enormously when you want to carry out works, because many alterations affect the building structure or common parts — and the freeholder’s consent is required.

Do You Need Freeholder Consent for Flat Renovations?

Almost certainly yes, for anything beyond cosmetic decoration. Your lease will contain a “licence to alter” or “consent to alterations” clause. Read your lease carefully (or have a solicitor review it) to understand specifically what requires the freeholder’s consent. Typical provisions include:

• Any structural alterations (removing walls, inserting beams, new openings)
• Alterations affecting common parts or shared services (gas, water, electrical risers)
• Changes to the external appearance of the building
• Installation of new plumbing, drainage, or wet rooms (which could cause water damage to lower floors)
• Changes to the floor covering (hard floors in upper flats can cause noise issues for neighbours)

Even seemingly internal works like removing a partition wall can require consent if the wall carries any load — and in many converted Victorian houses, internal walls may be structural.

The Licence to Alter Process

The formal process for obtaining freeholder consent is called a Licence to Alter. Here’s how it typically works:

1. Submit a Formal Request

Submit drawings and a description of the proposed works to the freeholder (or their managing agent). In practice, you’ll need at least:

• Existing and proposed floor plans
• A description of all proposed works
• Structural engineer’s report for any structural alterations
• Method statement for how the works will be carried out

2. Freeholder Reviews and Appoints Their Own Surveyor

The freeholder will typically appoint their own surveyor or structural engineer to review the proposals and confirm they are acceptable. You will usually have to pay the freeholder’s professional fees for this review — typically £500–£2,000 depending on complexity. This is standard practice and usually non-negotiable.

3. Conditions of Consent

Consent is usually given subject to conditions, including:

• Works must be carried out by contractors with appropriate insurance
• Any damage to common parts or other flats must be made good
• Building Regulations approval must be obtained
• The freeholder’s surveyor may require an inspection during or after works
• Specific acoustic requirements (e.g., for floor coverings)

4. The Licence Document

Formal consent is usually documented in a Licence to Alter — a legal document drafted by the freeholder’s solicitors (again, at your cost — typically £500–£1,500). You should ensure you obtain the formal Licence, not just informal email approval. The Licence stays with the property and provides evidence of legitimate works if you sell.

Can You Extend a Leasehold Flat?

Extending the physical footprint of a leasehold flat — adding floor area — is rarely straightforward. A few scenarios:

Roof Space (Top Floor Flats)

If you own the top floor flat, you might consider extending into the roof space to create a loft conversion. However: the roof usually belongs to the freeholder. To convert the loft, you would need to either purchase the roof space from the freeholder or negotiate a variation to the lease. This is possible but complex and expensive — expect to pay the freeholder a premium for the additional space, plus legal costs. Your architect can advise on feasibility.

Ground Floor Flats and Garden

If you own a ground floor flat with exclusive use of a rear garden, some leases permit the leaseholder to build an extension into the garden — but again, the freeholder’s consent is required, and any planning permission must also be obtained. In London, planning permission for an extension to a flat is almost always required (flats have very limited Permitted Development rights).

Internal Reconfiguration

The most common and achievable form of “extending” a leasehold flat is internal reconfiguration — making better use of the existing floor plate by removing walls, reconfiguring rooms, and opening up kitchen-dining spaces. This doesn’t require planning permission (for internal works) but does require the Licence to Alter for structural changes, and Building Regulations for any notifiable works.

Planning Permission for Leasehold Flat Works

Internal works to a leasehold flat generally do not require planning permission. However, external alterations — including any physical extension, changes to windows, or roof alterations — do require planning permission in most cases, because:

• Permitted Development rights for flats are very limited compared to houses
• Most external alterations to flats in London require a full planning application
• In conservation areas, even minor external changes may require planning permission

Note that freeholder consent and planning permission are separate requirements — you need both, and obtaining one does not guarantee the other.

Common Pitfalls to Avoid

Starting Work Without Consent

This is the most serious mistake. If you carry out alterations without freeholder consent, the freeholder can require you to reinstate the property to its original state — at your expense. This can cost tens of thousands of pounds. When you sell, solicitors conducting searches will identify any breach of the lease, which can prevent a sale proceeding or significantly delay it.

Assuming Internal Works Don’t Need Consent

Many leaseholders assume that because works are entirely internal and don’t affect the building structure, they don’t need consent. But many leases require consent for any alterations that affect the layout of the flat, new wet rooms, or changes to services — even if purely internal. Read your lease.

Not Getting Building Regulations Approval

Notifiable works (structural alterations, new electrical circuits, new plumbing installations, changes to heating systems) require Building Regulations approval regardless of freeholder consent or planning permission. Retrospective Building Regulations approval may not always be available and can complicate sales.