Six Issues That Could Make Your Property Unmortgageable

Selling can become significantly more complicated if a lender refuses to approve a buyer’s mortgage. We take a look at new research identifying six common issues that can leave a property unmortgageable, reducing the pool of potential buyers and, in some cases, affecting property values.

The analysis examined a range of structural, legal and environmental issues that lenders commonly consider during the mortgage approval process. Some of these issues may only come to light once a sale is underway, increasing the risk of delays, renegotiation or a failed transaction.

Non-standard construction carries the greatest financial impact

Among the issues assessed, non-standard construction was estimated to have the greatest impact on property values.

Properties built using concrete, timber framing, steel systems or other unconventional construction methods can prove more difficult to finance due to lender concerns around durability, maintenance and resale. The research estimates that such properties could see values reduced by around 30 per cent, equivalent to £83,664 based on the current average UK property price of £278,880.

Structural issues remain a major concern

Structural problems also featured prominently in the research.

Severe damp, subsidence and significant structural movement can all affect mortgage lending decisions, with the analysis estimating that these issues could reduce property values by at least 20 per cent, or around £55,776.

Short lease properties were also highlighted as a common issue. Leasehold properties with fewer than 70 to 80 years remaining may struggle to secure mortgage finance, potentially reducing property values by around 15 per cent, or £41,832.

Legal and environmental risks

The research also identified defective property titles as a significant legal barrier to mortgage approval.

Historic conveyancing errors, unresolved Land Registry discrepancies or uncertainty surrounding ownership rights could reduce property values by an estimated 12.5 per cent, equivalent to £34,860.

Environmental hazards, including flood risk and invasive plants such as Japanese knotweed, also remain a concern. According to the analysis, these issues could reduce property values by around 10 per cent, or £27,888.

Spray foam insulation under scrutiny

Spray foam insulation continues to present challenges for some property owners looking to sell.

According to the research, some lenders are declining mortgage applications on properties with spray foam insulation in the roof space due to concerns about ventilation, hidden timber damage and the ability to inspect the roof structure.

In some cases, sellers may need to remove the insulation before a transaction can proceed. The research estimates that around 250,000 properties may have been affected.

Commenting on the findings, Chris Hodgkinson, Managing Director of House Buyer Bureau, which produced the research, said: “One of the biggest shocks for many sellers is discovering that an issue they may have lived with for years suddenly becomes a major problem once a buyer’s lender gets involved.

In the current market, lenders are being increasingly cautious, and anything that raises questions around value, structural integrity, legal ownership or future resale potential can quickly derail a sale.”

See the original article on Properista

Published: 24 July 2026