Buying a Flat? What You Need to Know Before You Apply for a Mortgage

Flats can be a smart route into homeownership — but the mortgage process involves more checks than many buyers expect. Here’s what to get to grips with before you make an offer.

Lenders assessing a flat mortgage don’t just look at your income and deposit — they also assess the building, its lease arrangements, and the ongoing costs tied to ownership. Getting familiar with these factors early can save a significant amount of time, money and disappointment.

1. Lenders evaluate the building, not just the flat

When you apply for a mortgage on a flat, your lender is assessing two things: whether you can afford the loan, and whether the property is suitable security for it. With flats, that second question is considerably more involved than it is with a house.

The height and construction of the building, its communal facilities, the balance of owner-occupiers to renters, and the ownership structure all influence whether a lender will proceed — and on what terms. Two flats with near-identical asking prices can receive entirely different treatment simply because of the buildings they sit in.

2. Building height and design can restrict your options

Lenders are most comfortable with lower-rise buildings. Converted houses and purpose-built blocks of up to four storeys are accepted by most mainstream lenders without issue. Once a building exceeds four storeys, criteria typically tighten. Buildings with external deck access, a high proportion of rented flats, or those considered harder to resell tend to attract additional scrutiny.

For taller buildings, there’s also a building safety dimension to consider. Since the Building Safety Act 2022, properties of five storeys or over 11 metres face stricter checks. For buildings over 18 metres, lenders will typically want to see an EWS1 form — a fire safety assessment of the external walls — before they’ll lend, particularly where cladding is present. If you’re buying in a taller block, check early whether this documentation exists. If it doesn’t, transactions can stall significantly while it’s obtained.

3. Lease length matters more than most buyers realise

Most flats in England and Wales are sold as leasehold. Lease length is one of the most closely scrutinised aspects of any flat purchase — as the remaining term shortens, the property becomes harder to mortgage and harder to sell. Most lenders begin tightening criteria below 85 to 90 years, and the 80-year mark is particularly significant: once a lease falls below it, the cost of extending rises considerably.

When viewing a flat, always establish the remaining lease length and the ground rent terms. Older leases with escalating ground rents — doubling every ten or fifteen years — can be refused by lenders entirely. If a lease extension is needed, factor the cost into your budget before you commit.

There is some positive news: under the Leasehold and Freehold Reform Act 2024, leaseholders no longer need to wait two years before extending their lease. Further reforms — including a proposed cap on ground rents and the longer-term ambition to replace leasehold with commonhold for new flats — are in progress, though leasehold remains the norm for existing flat stock.

4. A larger deposit can open more doors

Deposit size carries particular weight when buying a flat with any complexity — a higher-rise building, a shorter lease, or elevated service charges. Reaching 15% or more can meaningfully improve both the lenders available to you and the rates on offer, and for properties at the more complex end of the spectrum, it can sometimes be the difference between approval and decline.

It’s also worth noting that stamp duty thresholds changed in April 2025. First-time buyers now pay stamp duty on properties above £300,000, down from the previous threshold of £425,000 — so the total upfront cost of buying is higher for many, and that needs to be built into your planning from the start.

5. Service charges are part of your affordability calculation

Mortgage lenders include service charges, maintenance fees and ground rent when assessing what you can afford. A flat with a manageable mortgage payment can still result in a lower loan offer if building costs are high — so the full picture matters.

Service charges have risen sharply in recent years. Research by Hamptons put the average annual charge at £2,405 in 2025, up 33% over five years and ahead of inflation. Many blocks built in the 1990s and early 2000s are now reaching the age where roofs, lifts and windows need major attention, and where sinking funds fall short, those costs land directly with leaseholders.

Before making an offer, ask for three years of service charge accounts and find out whether any significant works are planned. The management information pack your solicitor requests should contain this, but asking early means you’re not surprised later.

6. Shared Ownership carries costs that aren’t always obvious

Shared Ownership lets buyers purchase a share of a property — typically between 25% and 75% — while paying rent on the remainder. It’s an accessible route onto the ladder, but there’s a commonly misunderstood cost reality: regardless of the share you own, you are generally responsible for 100% of the service charges and maintenance costs.

For buyers who’ve entered schemes with initially affordable monthly costs, subsequent service charge increases can fundamentally undermine that affordability. A cross-party committee of MPs has described some Shared Ownership arrangements as failing to deliver a genuinely affordable route to homeownership, with service charges representing an uncapped and unpredictable liability. Go in with clear sight of the current charges, their recent history, and any anticipated works.

A quick checklist before you make an offer

• How many storeys is the building? Taller blocks face stricter mortgage criteria and may need fire safety documentation.
• What is the construction type? Non-standard methods can limit lender choice.
• What is the remaining lease length? Aim for at least 100+ years. If shorter, cost up an extension first.
• What are the ground rent terms? Escalating ground rents can be refused by some lenders.
• What are the service charges, and what is the sinking fund position? Request three years of accounts.
• What proportion of the block is owner-occupied? A low figure can reduce lender appetite.
• For taller buildings: is EWS1 documentation in place? Verify before progressing the purchase.
• If Shared Ownership: what is the full monthly cost? Mortgage payment, rent on the unsold share, and service charges combined.

We can help you make sense of it

Most of the issues above are identifiable early — and with the right mortgage advice, many can be navigated successfully. At Impact Specialist Finance, we work with buyers across a wide range of property types and personal circumstances.

If you’re considering a flat and want to understand your options before you make an offer, get in touch.