Non-Standard Construction Mortgages

Edited: February 2026

Non-standard construction mortgages can feel confusing, largely because the term covers a wide range of property types. Some non-standard properties are perfectly mortgageable, others require specialist lending, and some are not suitable for mortgage finance at all.

Understanding the construction type early is critical. It can affect lender choice, borrowing limits, valuation outcomes, and long-term resale prospects. This guide explains what non-standard construction means, how lenders assess it, and when a mortgage may or may not be possible.

At GPS Financial, we regularly advise buyers, landlords, and investors on non-standard construction properties and help identify the most appropriate funding route.

What Is Non-Standard Construction?

A property is classed as non-standard construction when it is not built using traditional brick or stone walls with a slate or tiled roof.

Large numbers of non-standard homes were built in the UK after the Second World War to replace bomb-damaged housing and clear slum areas quickly and affordably. Councils adopted system-built and modular methods, often using concrete, steel, or prefabricated components.

As a result, a significant number of non-standard construction properties still exist across the UK today.

How Difficult Is It to Get a Mortgage on a Non-Standard Construction Property?

There is no single rule. Mortgageability depends entirely on the specific construction type.

Reinforced concrete construction is a common example. Some systems, such as Airey houses, used concrete panels reinforced with steel. Certain materials used at the time can react with steel over time, leading to corrosion, often referred to as concrete cancer. Properties classed as defective under legislation are generally not mortgageable.

Other concrete systems are treated differently. For example, Laing Easi-Form properties were built using in-situ poured concrete and are widely accepted by mainstream lenders.

Steel-framed and timber-framed properties are also classed as non-standard. Some are acceptable to lenders, others require specialist finance, and some are not suitable for mortgage lending at all.

The key point is that lender appetite varies significantly by construction type, not by label alone.

What Does Prefabricated Construction Mean?

Prefabricated, or system-built, homes are manufactured off-site and assembled on location.

This method allows faster construction and consistent quality and is widely used in both residential and commercial development today. However, older prefabricated systems vary widely in durability and lender acceptance.

Whether a prefabricated property is mortgageable depends on the system used, the materials involved, and whether the construction type appears on lender-accepted lists.

Does the Same Apply to Buy to Let Properties?

Yes. The principles are the same for Buy to Let mortgages.

Provided the property is not classed as defective under Part 16 of the Housing Act 1985 in England and Wales, or has been repaired and certified under an approved scheme, mortgage options may be available.

Lenders rely heavily on accepted construction guidance, including information published by UK Finance.

You can read more about Buy to Let lending here

Are Barn Conversions Classed as Non-Standard Construction?

In most cases, no.

Barn conversions are often built with thick stone or brick walls and are usually classed as standard construction. Each property is assessed individually, but many barn conversions are mortgageable with mainstream lenders.

Roof materials, structural alterations, and compliance with building regulations will still be considered during valuation.

How Easy Is It to Get a Mortgage on Non-Standard Construction?

Ease of borrowing depends on the property type and lender appetite.

• Laing Easi-Form properties are widely accepted by high-street lenders
  • British Iron and Steel Federation houses are steel-framed and usually require specialist lenders, with lower loan to value limits and higher interest rates
  • Some non-standard properties require commercial-style lending
  • Others are not mortgageable at all

This variation is why early advice is essential before committing to a purchase or refinance.

What Advice Should Buyers and Investors Follow?

If you are considering a non-standard construction property, identify the construction type as early as possible. UK Finance publishes guidance on construction types that lenders consider acceptable or defective.

Non-standard construction should not automatically be discounted, particularly by experienced investors or developers.

In high-value areas, defective properties may be available at a significant discount. Some investors purchase these properties with cash, remove defective elements, and rebuild using brick and block to create a standard construction home.

The key is careful analysis. If the end value comfortably exceeds total purchase and build costs, non-standard construction properties can present strong opportunities.

Where short-term funding is required before works or refinance, bridging finance may be relevant

How GPS Financial Can Help

At GPS Financial, we regularly advise on mortgages for non-standard construction properties.

We assess lender appetite early, identify suitable funding routes, and explain clearly where risks exist. Our role is to help you understand whether a property is mortgageable, requires specialist lending, or should be approached with caution.

Frequently Asked Questions

Are all concrete houses unmortgageable?
No. Some concrete systems are classed as defective, while others are widely accepted. Mortgageability depends on the specific construction method.

Can I get a Buy to Let mortgage on non-standard construction?
Sometimes. The same construction rules apply, but lender choice may be more limited and loan to value caps may be lower.

Do non-standard construction mortgages cost more?
They often do. Specialist lending usually involves higher interest rates and lower maximum borrowing levels due to increased risk.

Can non-standard properties be repaired to become mortgageable?
In some cases, yes. Properties repaired and certified under approved schemes may become acceptable to lenders.

Should I avoid non-standard construction entirely?
Not necessarily. With the right knowledge and pricing, non-standard construction can offer strong investment opportunities.

Will all lenders treat the property the same way?
No. Lender appetite varies significantly, which is why broker advice is essential.

Speak to GPS Financial

If you are considering buying or refinancing a non-standard construction property and want clear, practical advice, speak to the team at GPS Financial.

We will review the construction type, explain your mortgage options, and help you decide the most appropriate route forward.

Call 029 2267 7707 or visit our Contact page