12 Reasons Lenders Refuse a Mortgage on Your House in 2026

By Lisa Hayes · 29 August 2026

The consumer group Which? has published a list of 12 reasons mortgage lenders say no, drawn from conversations with the lenders themselves. Read it as a buyer and it looks like a list of things to worry about. Read it as a seller and something else jumps out: almost every reason is about the house, not the person buying it. Your buyer can have a clean credit file, a 25% deposit and a decision in principle, and still be refused a loan — because of your lease, your loft insulation, your floor area or your postcode's flood map.

That's the part most sellers never see coming. You accept an offer, you feel the relief, and six weeks later the sale dies for a reason nobody mentioned at the viewing.

What did Which? actually say?

Which? set out twelve grounds on which a lender may refuse, illustrating several with the published criteria of named lenders. The list, reported by Estate Agent Today on 28 August 2026, covers down valuation, leasehold issues, number of storeys, spray foam insulation, cladding, flood risk, flats above commercial premises, flying freehold, unusual construction, Japanese knotweed, subsidence risk, and a property simply being too small.

None of that is a policy change. What's new is seeing it collected in one place with the actual numbers attached. Sellers tend to picture a mortgage refusal as something that happens to a buyer who overreached. It isn't. It's a surveyor's report meeting a lending policy document, and the thing being judged is your house.

Why your buyer's mortgage refusal is your problem

Here's the mechanic that catches people out. A decision in principle is a lender saying "this borrower looks fine". It is not a lender saying "and we'll lend on that house". The property assessment happens later — after the offer, after the survey is booked, after you've told your own vendor you're proceeding and possibly after you've paid for searches on the place you're buying.

When the refusal lands, you don't just lose a buyer. You lose the six to eight weeks you spent with them. Your listing goes back on the portals carrying the quiet stigma of a property that was sold subject to contract and then wasn't. Buyers notice that. Agents notice it. And if you were in a chain, the collapse travels in both directions, which is why the fallout is usually worse than the delay itself. We've written separately about what your options are when a chain collapses, because it's the single most common reason people come to us.

The uncomfortable truth: most sellers learn about a lending obstacle from a stranger's valuation report, several weeks too late, at the point where it costs the most.

The 12 reasons, and what each means if you're selling

Take them one at a time, because your response is different in each case.

1. Down valuation

The surveyor decides your house isn't worth what your buyer agreed to pay. The lender re-offers on the lower figure, and your buyer has to find the shortfall in cash, renegotiate, or walk. Which? says you can appeal by supplying evidence: recent sale prices of comparable homes in the same area, ideally similar in size, condition and location, and sold within the past six months.

That advice sounds procedural. It's the most useful line on the whole list, because it tells you exactly what a surveyor will accept. If you can't find three genuine comparables from the last six months that support your asking price, your asking price is a hope rather than a valuation. Far better to know that before you list. Our guide on how much your house is really worth walks through building that evidence yourself.

2. Leasehold issues

Which? says lenders' limits vary, but broadly they won't lend where fewer than 50 to 90 years remain on the lease. Ground rent clauses that escalate sharply over time are a separate problem, because they hit resale value — and the lender is thinking about resale, not about you.

If you own a flat with a lease in the eighties, you're closer to trouble than it feels. Extending is expensive and slow, but it's a known quantity. A collapsed sale in November isn't. If you're weighing the tenure question at all, freehold versus leasehold for a quick sale sets out how each behaves under time pressure.

3. Number of storeys

Nationwide will not lend on former local authority flats in blocks of more than five storeys, according to Which?. Other flats in buildings above five storeys with lift access may be accepted, depending on the valuer's assessment.

This one is pure lottery from the seller's side. You cannot change the height of your block. What you can do is establish early which lenders will and won't play, then price and market accordingly. A flat only three lenders will touch has a smaller buyer pool, and pretending otherwise burns months.

4. Spray foam insulation

Some lenders decline outright. NatWest, Which? notes, will consider properties with spray foam but assesses them case by case, subject to the valuer's comments.

Spray foam has killed more sales in the past three years than almost any other single retrofit. If it went into your loft under a grant scheme and you still have the paperwork, dig it out now. Without an installation certificate and a surveyor's view on the roof timbers, expect the question, and expect it to cost you weeks.

5. Cladding

Lenders aim to be flexible, Which? says, but they need to factor in potential costs or see confirmation that a developer will cover remediation. Understanding the position early shapes the entire conversation and clarifies what paperwork exists.

If you own a flat in an affected block, the building's remediation status is effectively part of your title now. Chase your managing agent for the current position in writing before you instruct an agent, not after you've accepted an offer.

6. Flood risk

Lenders use mapping technology to identify homes vulnerable to flooding, and a high-risk designation can mean a flat refusal.

The maps are public. Check yours. If your home sits in a flagged zone but has never flooded, or has had defences installed since the mapping was done, gather the evidence — claims history, insurance position, any local scheme documentation — and hand it to your agent on day one.

7. Above commercial premises

Nationwide will consider these based on the valuer's read of noise, smells, anti-social opening hours and fire risk, alongside local demand and location, Which? reports.

Note the wording. It isn't "above a shop, refused". It's a judgement call. A flat above a quiet accountant's office is treated very differently from one above a late-night takeaway. If yours is the former, say so plainly in the listing.

8. Flying freehold

Where part of your property sits over land you don't own — typically a bedroom above a shared passage. Leeds Building Society will lend where the flying freehold accounts for 15% or less of the property, Which? reports. Other lenders set their own share.

Get the percentage established by your solicitor before marketing. "It's only a small part" is not a number a lender can act on.

9. Unusual construction

Anything non-standard creates difficulty, because certain construction types carry known histories. Pre-cast concrete is the example Which? gives: it can deteriorate over time and may require significant remedial work.

PRC, timber frame, steel frame, cob, thatch — each has its own small circle of willing lenders. If your home is in that category, you probably half-know it already. The mistake is marketing to the whole market and then acting surprised.

10. Japanese knotweed

This is the genuinely good news on the list. Which? states knotweed is no longer an automatic decline. Many lenders will now consider an application where an appropriate treatment plan is already underway, carried out by a recognised specialist and covered by an insurance-backed guarantee.

Read that carefully, because the conditions do the work: "already underway", "recognised specialist", "insurance-backed guarantee". A DIY glyphosate campaign and a photo of a bare border won't do it. If you think you have knotweed, our guide to identifying it is the place to start, and a proper treatment contract is what turns a dead sale into a live one.

11. Subsidence risk

NatWest lists geological issues among the environmental factors a valuer may identify, including the presence of gases and past or present coal and other mining operations, according to Which?.

Historic movement that's been underpinned and monitored is a completely different proposition from live, unexplained cracking. The difference is documentation. With engineer's reports, a completion certificate and continuous insurance, you have a sellable house. Without them, you have a project. We've set out the realistic routes in our guide to selling a house with subsidence.

12. Your home is too small

Some lenders set a minimum floor area they won't go below. Skipton Building Society requires at least 30 square metres, Which? reports.

Thirty square metres is a studio. If you own one, your buyer pool is smaller than the viewing numbers suggest and skews heavily towards cash. That's not a disaster. It's a marketing fact you should know before you set a price.

The named lender criteria, in one place

These are the specific figures Which? attributes to individual lenders. Criteria change, and every case turns on the valuer's report, so treat this as the start of a conversation with a broker rather than a rulebook.

Issue	Lender named by Which?	Stated position
Minimum floor area	Skipton Building Society	Won't lend below 30 square metres
Flying freehold	Leeds Building Society	Will lend where it affects 15% or less of the property
Ex-council flats in tall blocks	Nationwide	No lending on former local authority flats in blocks over five storeys
Flats above commercial premises	Nationwide	Considered, subject to the valuer's view on noise, smells, opening hours, fire risk and local demand
Spray foam insulation	NatWest	Case by case, subject to the valuer's comments
Subsidence and mining	NatWest	Geological factors, including gases and mining, may be flagged by the valuer
Lease length	Varies by lender	Generally won't lend with less than 50 to 90 years remaining
Japanese knotweed	Many lenders	No longer an automatic decline where treatment is underway with an insurance-backed guarantee

Why this bites harder in the autumn 2026 market

Timing matters. A lending obstacle in a hot market is an inconvenience, because there's another buyer standing behind the first. In this market there often isn't.

Zoopla's August House Price Index, published on 27 August, puts UK annual house price growth at 0.9% in the year to July, down from 1.3% in June, with the average home at £272,800. Buyers are coming back — searches are 7% higher than a year ago, the strongest annual increase in twelve months — but sales agreed remain 6% down, and there are 5% more homes on the market than last year.

• £272,800average UK house price, July 2026
• 0.9%annual price growth, down from 1.3% in June
• 4.8%typical five-year fixed rate, up from below 4% in January
• 9%fall in buyer purchasing power since January

That last figure is the one to hold onto. Zoopla calculates that a buyer who could afford a £200,000 mortgage in January can now borrow around £182,000 for the same monthly repayment — or would need to find an extra £18,200 in deposit to buy the same home. In London the gap is around £35,500. In the North East, where prices are lower, it's about £10,200.

Squeeze buyers that hard and two things follow. They have no headroom left to absorb a down valuation, so a £10,000 shortfall that would once have been shrugged off now kills the deal. And with more homes for sale than buyers chasing them, a seller whose property carries a lending complication is competing against a dozen that don't.

Which homes are most exposed?

Flats, mostly. The overlap between the Which? list and the flat market is uncomfortably neat: lease length, cladding, storeys, above-commercial, minimum floor area. Five of the twelve are flat-specific or flat-heavy.

The Zoopla numbers show where that lands. Flats and maisonettes are the only property type going backwards, down 1.6% over the year to an average of £191,800, while semi-detached homes are up 1.6% at £282,000 and detached up 1.1% at £458,100. Some of that is affordability, and some is the service charge and ground rent story. But part of it is simply that a smaller pool of lenders will lend on a flat, and a smaller pool of lenders means a smaller pool of buyers, which means softer prices.

Property type	Average price, July 2026	Annual change
All property	£272,800	+0.9%
Detached	£458,100	+1.1%
Semi-detached	£282,000	+1.6%
Terraced	£242,000	+1.1%
Flats and maisonettes	£191,800	−1.6%

Geography compounds it. Prices are 1% lower than a year ago in London and 0.3% lower across the South East, according to Zoopla, while the North West is up 3.1%, Yorkshire and the Humber up 1.7% and Northern Ireland up 5.4%. So if you own a leasehold flat in the South, you're selling the most lender-sensitive property type in the weakest regional market at the exact moment buying power dropped 9%. That's not a reason to panic. It's a reason to prepare properly.

What to do now if you're selling

The real value of the Which? list is as a pre-flight check. Work through it before you go to market, not after your buyer's survey comes back.

Get your comparables together first. Three genuine sold prices from the last six months, similar size, similar condition, same area. If they support your number, you have a ready answer to a down valuation. If they don't, adjust your price now and save yourself two months.

Read your own lease. Term remaining, ground rent, review clauses. If it's under 90 years, get a quote for extending and know the cost before a buyer asks.

Collect the paperwork nobody wants until it's urgent. Spray foam installation certificates. Knotweed treatment contracts and guarantees. Underpinning completion certificates and insurance continuity. Cladding remediation status in writing from the managing agent. Building regs for anything structural. Each one turns "we can't lend" into "we can lend, subject to".

Ask your agent which lenders will lend on your property type. A good agent knows. If yours doesn't, that tells you something too.

Qualify the buyer, not just the offer. A decision in principle is worth asking for, but it's not proof the lender will lend on your house. Ask which lender. Ask whether the buyer's broker has checked that lender's criteria against your property type. Ask what's behind them in the chain.

When does a cash buyer actually make sense?

Let's be straight about this, because it's the part of the conversation where the industry usually turns slippery.

A cash buyer doesn't need a lender. That removes the survey-meets-lending-policy problem entirely: no down valuation, no minimum floor area, no five-storey rule, no lease-length cut-off. For a property that trips two or three items on the Which? list, that isn't a marketing line. It's the difference between selling and not selling.

It also costs you money. Genuine cash buying companies buy below market value, and anyone telling you otherwise is selling something. The honest question isn't "is it cheaper?" — it isn't — but "what is the alternative actually worth, after the months it takes and the risk it fails?" A studio under 30 square metres with a 78-year lease may sit on the open market all autumn, attract one offer, and lose it at valuation stage. Weigh the discount against that, not against a fantasy sale.

If you're working through the maths, what percentage of market value cash buyers pay in 2026 gives the real ranges, and our guide to whether cash house buyers are a good idea covers where the route goes wrong. For most sellers with a straightforward freehold house, the open market is still the right answer. For sellers with a lending complication, a broken chain or a hard deadline, it stops being an emergency option and becomes a reasonable one worth pricing up.

What happens next

Zoopla expects annual price growth to slow towards around 1% by the end of the year, with the North of England and Scotland holding up better than London and the South East. Mortgage rates are the swing factor. They've settled near 4.8%, and any move down would feed straight into first-time buyer demand, which is where the market is thinnest right now.

Lending criteria don't loosen quickly. Lenders relaxed on knotweed only after years of evidence about treatment plans. Expect cladding to follow the same slow path as remediation completes, and expect spray foam to stay difficult until there's a recognised inspection standard. If your property has one of these issues, plan on the rules looking much the same next spring.

None of which is a reason to sit still. Buyers are back in numbers not seen for a year. They're just more selective, and they're borrowing against a shorter tape measure.

The bottom line

A mortgage refusal feels like something that happens to your buyer. It happens to your house. Twelve reasons, nearly all of them visible from your own front door, and every one cheaper to sort out in August than in November with a broken chain behind you.

Go through the list. Find your paperwork. Get three comparables. Then decide, with your eyes open, whether the open market is right for the property you actually own — or whether it's worth seeing what a guaranteed offer looks like alongside it. Comparing the two costs nothing: start with a valuation and take it from there. If you'd rather read up first, our guides on selling a house fast and UK house prices in 2026 cover the ground in more detail.

Lisa Hayes is the founder of Ready Steady Sell. We're independent — we don't buy houses and we're not an estate agent.