Lease Extensions Explained: The Complete Guide for London Leaseholders

London has one of the highest concentrations of leasehold properties in the UK — and the capital's love of period flat conversions means that many buyers find themselves acquiring a property with a lease that is already ticking down. Understanding lease extensions — when you need one, how much they cost, and how the process works — is essential knowledge for any London flat owner or buyer.

Why Does Lease Length Matter?

When you own a leasehold flat, you own the right to occupy the property for the duration of the lease term. When the lease expires, ownership reverts to the freeholder. This means that a short lease significantly affects the value and saleability of a property:

• Leases under 80 years begin to attract a significant premium on extension (called "marriage value"), making extensions considerably more expensive
• Most mortgage lenders require a minimum of 70–80 years remaining on the lease at the end of the mortgage term — meaning a 25-year mortgage typically requires 95–105 years on the lease today
• Properties with short leases are difficult to sell — many buyers simply can't get a mortgage on them
• The shorter the lease, the lower the property value — sometimes dramatically so below 70 years

The key threshold to be aware of is 80 years. Once the lease drops below this, marriage value becomes payable on a statutory extension, often adding tens of thousands of pounds to the cost. If you are considering purchasing a property with less than 85 years remaining, we strongly advise getting a lease extension underway as soon as you are legally able to.

The Two Routes to Lease Extension

1. The Statutory Route (Leasehold Reform, Housing and Urban Development Act 1993)

Under the 1993 Act (as amended), qualifying leaseholders have the legal right to extend their lease by 90 years on top of the existing unexpired term, at a peppercorn ground rent (i.e., zero). To qualify, you must have owned the leasehold property for at least two years.

The statutory process is as follows:

1. Instruct a specialist leasehold valuation surveyor to carry out an RICS valuation of the lease extension premium
2. Instruct a specialist leasehold solicitor to serve the Section 42 Notice on the freeholder (the formal notice of your claim to extend)
3. The freeholder has two months to serve a Counter Notice setting out their terms
4. Negotiations on the premium take place between the surveyors — most cases are resolved at this stage
5. If agreement cannot be reached, either party can apply to the First-tier Tribunal (Property Chamber) for a determination
6. Once agreed, the solicitors draft and complete the new lease

The whole process typically takes 6–12 months, although straightforward cases can be concluded more quickly.

2. The Informal Route

Alternatively, you can simply approach your freeholder informally and negotiate an extension without invoking your statutory rights. This can be quicker and less expensive in terms of legal costs — but you have no statutory protection, the freeholder can offer any terms they wish (including an increased ground rent), and you do not have the security of the tribunal as a backstop.

Many freeholders and management companies are willing to negotiate informally, particularly for longer leases. For leases below 80 years, however, the statutory route generally offers better protection and is usually advisable.

How Is the Lease Extension Premium Calculated?

The statutory premium for a lease extension under the 1993 Act is calculated using a complex valuation formula that takes into account:

• Ground rent capitalisation: The present value of the ground rent income the freeholder will lose
• Reversion value: The present value of the freeholder's right to repossess the property at the end of the current lease term
• Marriage value: The increase in the combined value of the freehold and leasehold created by the extension (only payable when the lease has less than 80 years to run — split 50/50 between leaseholder and freeholder)

This is a specialist area of valuation that requires expert knowledge of the relevant legislation, case law, and applicable valuation methodology. Our RICS Registered Valuers can prepare an independent valuation of the likely premium, advise on negotiation strategy, and if necessary represent you at tribunal.

What Does a Lease Extension Cost?

The total cost of a lease extension typically includes:

Cost Item	Typical Range
Lease extension premium (statutory)	Varies widely — £5,000 to £50,000+ depending on lease, value and location
Your surveyor's fees	£1,000 – £2,500
Your solicitor's fees	£1,500 – £3,500
Freeholder's surveyor fees (you pay these)	£500 – £1,500
Freeholder's solicitor fees (you pay these)	£500 – £1,500
Land Registry registration fee	£20 – £500 (scale fee)

"The best advice I can give to anyone buying a leasehold flat in London with a short lease is: get a lease extension valuation done before you commit to purchase, and factor the full cost into your offer. A lease extension after purchase requires two years' ownership before you can serve a statutory notice — two years during which the lease is getting shorter."

Buying a Property with a Short Lease

If you are buying a leasehold flat with under 90 years on the lease, you have two main options:

• Ask the seller to extend the lease before completion (the seller needs to have owned the property for 2+ years)
• Ask the seller to assign their right to extend to you at completion, then serve notice immediately — known as "assigning the benefit of the Section 42 notice"

Both approaches require careful coordination between solicitors and surveyors. We strongly recommend obtaining specialist advice before proceeding.