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Timber frame, steel frame, concrete and thatched properties can be harder to mortgage, but they're rarely impossible. More than half of UK lenders consider non-standard construction, and a specialist broker can help you find the right one.
A non-standard construction mortgage is a mortgage for a property built using materials or methods that fall outside what lenders consider 'standard' - typically brick or stone walls with a tile or slate roof on concrete foundations.
The term 'non-standard' doesn't mean a property is poorly built. Many non-standard homes are well-constructed character properties, modern eco-builds, or solid post-war housing that's stood the test of time. It simply means lenders assess the property differently before offering a mortgage.
Finding a non-standard construction mortgage can feel harder than it should, especially when mainstream lenders keep saying no. The good news is that a wide range of UK lenders consider non-standard construction properties, and with the right approach you can find a competitive deal.
A non-standard construction property is any home built using materials or methods that fall outside what lenders consider 'standard' - which typically means brick or stone walls with a tile or slate roof resting on concrete foundations.
This definition covers a surprisingly wide range of properties. Your home might be non-standard because of its walls (timber frame, steel frame, concrete blocks, poured concrete), its roof (thatch, flat, shingle, eco-friendly), or the techniques used to build it (prefabricated, modular, kit-built, barn conversions). The housing shortage after the Second World War led to widespread use of modular elements and concrete blocks for rapid construction.
Non-standard construction properties include listed buildings, prefabricated steel builds, properties with concrete or glass walls, and those with thatched or eco-friendly roofing. The specific features and construction type of a property are crucial in identifying whether it's non-standard, and in working out the right mortgage options for it.
The term doesn't mean a property is substandard or poorly built. Many non-standard homes are beautifully constructed character properties, modern eco-builds using sustainable or natural materials such as clay, straw and limestone, or solid post-war housing that's stood the test of time. It simply means lenders need to assess the property differently when deciding whether to offer a mortgage.
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Quick reference
Timber-framed properties
An inner timber frame with an outer skin of brick, stone, render or timber cladding. One of the most common non-standard types, and widely accepted by lenders when built to modern standards.
Steel-framed properties
Includes post-war BISF houses and modern steel-framed builds. Lenders are mainly concerned with corrosion of the frame over time.
Concrete and PRC properties
Precast reinforced concrete (PRC) homes such as Airey, Cornish, Wimpey No-Fines and Reema houses. Many were designated defective and need a PRC certificate to be mortgageable.
Thatched properties
Carry a higher fire risk in lenders' eyes and need re-roofing every 15-30 years, but remain widely mortgageable with the right specialist insurance.
Flat-roofed properties
Common, but can raise concerns over drainage and lifespan. How much of the roof is flat, and its condition, both affect a lender's view.
Cob, wattle and daub, and other traditional materials
Historic properties built with natural materials like cob, wattle and daub, or clunch. These need specialist knowledge to maintain, repair and insure.
Modern eco-builds
Contemporary homes built with straw bales, hempcrete or sheep's wool insulation. Increasingly popular, and supported by a growing number of specialist and mainstream lenders.
Understanding your property's construction type precisely is the first step toward finding the right mortgage. Different construction methods carry different risk profiles in lenders' eyes, which affects both how many lenders will consider your application and the rate you're offered.
Timber-framed homes have an inner timber frame with an outer layer that could be brick, stone, render, or timber cladding. They're one of the most common non-standard construction types in the UK.
Modern timber-framed homes built after 1990 to NHBC or BBA standards are generally well accepted by lenders. The main concerns are fire risk and the potential for damp or rot, particularly in older properties built between the 1950s and 1970s when building regulations around vapour barriers were less stringent.
Many high-street lenders will consider timber-framed properties, especially those with a brick outer skin. You may need a damp and timber survey to satisfy the lender's requirements.
Steel-framed homes include British Iron and Steel Federation (BISF) houses built after the Second World War, as well as modern steel-framed constructions. The main concern is potential corrosion of the steel frame over time.
Lenders often want a structural engineer's report confirming the frame's condition. Some older steel frame types are more difficult to mortgage than others, and not every high-street lender will consider them.
Precast reinforced concrete (PRC) properties were popular for post-war housing, offering a quick, cost-effective building method. The housing shortage after the Second World War led to widespread use of modular elements, concrete blocks, and poured concrete for rapid construction. Issues such as 'concrete cancer' - where the concrete deteriorates and affects the integrity of the property - can arise in these types of buildings. They go by various names including Airey houses, Cornish units, Wimpey No-Fines, Laing Easiform, Reema, and Woolaway.
These properties present the biggest challenge for mortgage applicants. Many were designated as 'defective' under the Housing Act 1985 after problems were found with concrete deterioration and steel reinforcement corrosion.
If a PRC property has been repaired through an approved scheme and holds a PRC certificate, many lenders will consider it. Without this certificate, your options become much more limited, though specialist lenders can still help.
Thatched roofs present an elevated fire risk in lenders' eyes, and the roofing needs replacing every 15-30 years depending on the material used. This specialist maintenance requirement makes some lenders cautious.
That said, thatched properties remain mortgageable. A number of lenders will consider them, though you'll need specialist buildings insurance in place before completion.
Properties with flat roofs, or very low-pitched roofs, are common but can cause concern due to potential drainage issues and a shorter lifespan compared with pitched roofs. How much of the roof is flat matters too - a small extension is treated very differently to an entire flat roof.
Most lenders will consider properties with some flat roofing, but policies vary. A lower maximum loan-to-value is common for properties with substantial flat roof coverage.
Historic properties built with traditional materials like cob (subsoil, water, and organic material), wattle and daub (wooden strips covered with a clay mixture), or clunch (chalky limestone) require specialist knowledge to maintain and repair. These traditional methods use natural materials such as clay, straw, and limestone, which are environmentally friendly and provide good insulation.
These properties often have the charm and character that buyers love, but they need specialist insurance, and repairs typically need to be carried out using traditional methods. Lenders will want evidence that the property has been properly maintained.
Contemporary eco-homes built with sustainable materials - straw bales, hempcrete, sheep's wool insulation, or other modern methods - are increasingly popular but fall outside standard construction definitions.
Some specialist lenders actively support eco-friendly builds. Mainstream lenders are also becoming more open to modern methods of construction (MMC), particularly where proper warranties are in place.
Different names often describe the same construction method, so pin down exactly what you're dealing with before you apply. Is it timber-framed with a brick skin or full timber cladding? Is the concrete PRC, in-situ poured, or a large panel system? Getting this detail right from the start saves you from applying to the wrong lenders.
Understanding why lenders approach non-standard construction differently helps you prepare a stronger application. Each lender sets its own criteria for non-standard construction, and strict lending criteria can lead mainstream lenders to decline these applications or apply higher rates. Their concerns generally fall into a few key areas.
When you take out a mortgage, your property acts as security for the loan. If you can't keep up repayments, the lender needs confidence they can sell the property to recover their money. Non-standard properties may have a smaller pool of potential buyers and take longer to sell, which increases the lender's risk.
Standard brick-and-mortar houses have decades of sales data to support valuations. Non-standard properties are harder to value accurately because there are fewer comparable sales, and the condition of specialist construction elements can significantly affect price.
For non-standard construction mortgages, the property survey and valuation are crucial, as lenders rely heavily on the surveyor's assessment to make their lending decision.
Lenders require buildings insurance to be in place before they'll release mortgage funds. Non-standard properties typically need specialist insurance, which can be harder to arrange and more expensive. Finding comprehensive buildings insurance for non-standard properties is often more difficult and costly because of the perceived risks associated with unconventional materials. If the property can't be insured adequately, the lender won't proceed.
Some non-standard construction types have higher or more specialist maintenance requirements. Thatched roofs need regular attention, timber frames need protection from rot and pests, and concrete properties may need remediation work. Higher ongoing costs could affect your ability to maintain both the property and your mortgage payments.
Post-war prefabs were designed as temporary housing with a 10-year lifespan. Many have now stood for 70+ years, but lenders remain cautious about long-term structural integrity. Even well-maintained non-standard properties may face questions about their remaining useful life.
Requirements vary between lenders and depend on your specific property type, but here's what you can typically expect when applying for a non-standard construction mortgage.
As with any mortgage, your home may be repossessed if you do not keep up repayments on your mortgage or any other debt secured on it.
Most lenders require a minimum deposit of 10-15% for standard residential mortgages. For non-standard construction properties, the deposit required is often higher.
Putting down a larger deposit doesn't just improve your chances of approval - it can also help you access a better rate.
Standard mortgage valuations rarely suffice for non-standard properties. Lenders may require a comprehensive survey - such as a RICS Building Survey - rather than a standard valuation, to assess the condition, structural integrity, and risks of the property before approving a mortgage.
Expect one or more of the following:
These additional surveys cost more, but they provide vital information about whether your chosen property represents good value and what maintenance it might need.
You must have buildings insurance in place before completion. For non-standard construction, this typically means:
Get insurance quotes early in your property search. If insurance proves impossible or prohibitively expensive, it's a sign the property may also be difficult to mortgage.
Affordability requirements for non-standard construction mortgages mirror standard applications - lenders assess whether you can comfortably afford repayments based on your income, existing debts, and living costs.
Some lenders apply stricter income multiples for higher-risk non-standard properties, reflecting the additional risk they perceive. Speak to an advisor about how this might affect how much you can borrow.
A clean credit history becomes even more important when you're already presenting a higher-risk property. Lenders may be less flexible about adverse credit issues when combined with non-standard construction. That said, specialist lenders exist who consider both non-standard construction and credit challenges together.
If you're worried about your finances or want free, independent guidance, MoneyHelper (moneyhelper.org.uk, 0800 138 7777) can help.
If insurance proves difficult to arrange or unusually expensive, treat that as an early warning sign. Lenders won't release funds without adequate buildings insurance in place, so it's worth getting quotes as soon as your offer is accepted rather than waiting until you're close to completion.
Rates for non-standard construction mortgages are typically higher than standard residential rates, reflecting the additional risk lenders perceive. How much higher depends on the construction type and your individual circumstances.
As a general guide, non-standard construction mortgages tend to carry a rate premium over the best standard deals available at the time. Modern timber-framed properties with a brick skin, and properties with only minor flat roof extensions, often qualify for rates close to standard. PRC properties without remediation certificates, or unusual eco-builds, tend to sit at the higher end of the range.
Rates change frequently, so speak to an advisor for an up-to-date picture of what's available for your specific construction type.
The difference between lenders for non-standard construction can be dramatic. One lender might decline your application entirely while another offers competitive terms. A lender that specialises in timber-framed properties may price them very differently to one that only occasionally accepts them.
This is where working with a specialist broker makes a genuine difference - they know which lenders are likely to offer suitable terms for your specific construction type. Some specialist lenders only deal through an intermediary like a mortgage broker for non-standard construction cases.
A wide range of UK lenders consider some form of non-standard construction, but their criteria vary enormously. Each lender sets its own eligibility criteria, assessing factors such as property type, condition, and your individual circumstances. Many lenders decline non-standard construction applications outright, while others say approval depends on the valuer's assessment. What one lender accepts, another declines.
Several mainstream lenders will consider certain non-standard construction types, including timber frame, steel frame, thatched roofs, and some repaired PRC properties. Criteria differ significantly from one lender to the next, and a property declined by one high-street name may be accepted by another. Because criteria change regularly, it's worth confirming a lender's current position with an advisor before applying.
For more challenging non-standard construction, specialist lenders often provide solutions where high-street options fall short. Specialist lenders frequently work with specialist mortgage brokers, who have the expertise and relationships needed to navigate complex or niche cases.
Some construction types remain very difficult or impossible to mortgage:
Even with difficult construction types, don't assume the answer is always no. New specialist products appear regularly, and a broker with current market knowledge can advise whether options exist.
High-street lenders
The survey is crucial for non-standard construction mortgages. Lenders typically require a comprehensive survey and valuation before approving a mortgage on a non-standard construction property. This survey determines whether the lender proceeds, and it often influences the terms you're offered.
Budget £500-1,500 for comprehensive surveys and any specialist reports your lender might request. It's a real cost, but it's far cheaper than finding out about a structural problem after you've exchanged contracts.
Buildings insurance is a mortgage requirement, and for non-standard construction, this usually means specialist cover. Finding comprehensive buildings insurance for non-standard properties is often more difficult and costly, because of the perceived risks associated with unconventional materials.
Standard home insurance policies assume brick walls and tile roofs. They may not adequately cover:
Underinsuring your property creates problems. If something goes wrong, you could face a shortfall between what the insurance pays out and what repairs actually cost. Your lender requires adequate cover as a condition of the mortgage.
A number of insurers and brokers specialise in non-standard construction, covering everything from timber-framed and concrete homes to thatched cottages and eco-builds. When getting quotes, provide accurate information about:
Expect to pay more for non-standard construction insurance than for a standard property, though this varies significantly by construction type. Thatched properties often face the highest premiums because of fire risk. Well-maintained modern timber-framed homes may pay only slightly more than standard brick properties, and PRC homes with remediation certificates often achieve reasonable quotes.
Here's what tends to make the difference between an approval and a decline for non-standard construction mortgages.
Identify your construction type precisely. Different names describe the same construction method, and the details matter. Is it timber-framed with a brick skin or full timber cladding? Is the concrete PRC, in-situ poured, or a large panel system? A property survey can confirm the construction type and help you ask the right questions.
Check for PRC designation. If your property might be designated defective concrete, establish whether approved repairs have been completed. Ask the seller for documentation and check local authority records if needed.
Get insurance quotes early. If you can't insure the property, you can't mortgage it. Getting quotes before committing confirms the property is insurable at a reasonable cost.
Save a larger deposit if possible. Moving from a 15% deposit towards 20-25% can significantly improve your options for non-standard construction.
Gather documentation proactively. Collect any repair certificates, previous surveys, planning documents, or structural reports the seller has. Specialist documentation may also be required for the property's unique construction. A mortgage broker can help identify and manage what's needed, which speeds up the lender's assessment.
Address credit issues first. If you have any credit blemishes, work on improving your credit score before applying. Combining non-standard construction with credit issues limits your options.
Demonstrate affordability clearly. Have payslips, tax returns (if you're self-employed), and bank statements organised. Clear financial documentation helps offset property-related concerns.
Each declined application leaves a mark on your credit file. Applying speculatively to lenders without checking their criteria for your construction type wastes time and can damage your credit score.
Solution: work with a broker who knows which lenders accept your property type before any applications are submitted.
Basic mortgage valuations rarely suffice for non-standard construction. Buyers who budget only for a basic survey often face unexpected costs when lenders request structural reports.
Solution: budget £500-1,500 for comprehensive surveys and potential specialist reports from the outset.
Discovering at the last minute that your property is difficult or expensive to insure causes delays and stress. It can even collapse a transaction if cover can't be arranged.
Solution: get insurance quotes when your offer is accepted, not when you're approaching completion.
A modern timber-framed home with brick cladding and an unrenovated 1950s PRC bungalow face completely different lending environments. Treating all non-standard construction as equally challenging leads to poor strategy.
Solution: understand specifically what type of non-standard construction you're dealing with, and what it means for lending and insurance.
Non-standard construction properties often sell at a discount to standard equivalents. If you're paying full market value for a property that's difficult to mortgage and insure, you may be overpaying.
Solution: research comparable sales and factor in the limitations when negotiating your offer.
Finding the right mortgage for a non-standard construction property takes specialist knowledge that most high-street banks simply don't have.
We're a broker, not a lender. Our role is connecting you with specialists from our network who genuinely understand non-standard construction mortgages, and who know which lenders accept timber frames, which will consider PRC with certificates, and which offer suitable terms for eco-builds.
If we can't help, we'll tell you honestly and explain why.
What to expect
Tell us about your property
We'll discuss your property and circumstances to understand the construction type and any challenges.
We match you with a specialist
We'll connect you with a broker from our network who specialises in your property type.
Your broker researches your options
Your broker will research lenders, present your best options, and handle the application on your behalf.
You're supported through to completion
You'll have expert support throughout the process, right through to completion.
Common questions
Yes, in most cases. More than half of UK lenders will consider some form of non-standard construction. Your options depend on the specific construction type, property condition, and your financial circumstances. Working with a specialist broker significantly improves your chances of finding a suitable lender.
Usually, yes. Rates tend to be higher than the best standard mortgage deals, and how much higher depends on the construction type. Lower-risk non-standard construction, such as modern timber frame or minor flat roofing, typically attracts better rates than higher-risk types like unrenovated PRC or older steel frame. Speak to an advisor for current figures.
Typically 15-25%, though this varies by construction type. Modern timber-framed properties may qualify with a 10-15% deposit, while PRC or higher-risk construction often requires 20-25% or more. Larger deposits generally improve both your approval chances and the rate you're offered.
It's not strictly required, but using a specialist broker can significantly improve your chances of approval and often results in better terms. They know which lenders accept your construction type and how to present applications effectively.
At minimum, expect a RICS Homebuyer Report or full Building Survey. Lenders often require additional specialist reports depending on construction type - structural engineer's reports for steel or timber frames, damp and timber surveys, PRC certificates, or mundic tests in Devon and Cornwall.
It's very difficult but not always impossible. Most mainstream lenders won't consider unrepaired designated defective PRC properties. Some specialist lenders may help, but expect higher rates and larger deposit requirements. The most straightforward route is to buy a property that's already been repaired with a valid PRC certificate.
Not necessarily. Modern timber-framed properties built to NHBC or BBA standards are widely accepted by lenders, including many high-street names. Older timber-framed homes (1950s-1970s) or those with unusual cladding face more scrutiny but remain mortgageable through specialist lenders.
It can do. Non-standard properties typically have a smaller pool of potential buyers, because some people prefer to avoid the complexity of specialist mortgages and insurance. That said, many non-standard properties have strong demand - character thatched cottages, modern eco-homes, and well-maintained period properties all have dedicated markets.
Allow extra time compared with standard mortgages. Additional surveys, specialist valuations, and more detailed underwriting mean 6-10 weeks is realistic, sometimes longer for complex construction types or where remediation work needs arranging.
Yes, though you'll face similar considerations as with a purchase mortgage. If you've been making payments successfully and the property is in good condition, remortgaging is generally straightforward. An existing mortgage on the property also demonstrates it's mortgageable, which helps with lender confidence.
Almost always, yes. Standard home insurance policies are designed for brick and tile properties. Specialist insurers understand the unique risks and higher rebuild costs associated with non-standard construction, and a number of providers focus specifically on this market.
This depends on the severity. Minor issues might simply need monitoring or routine maintenance. More significant problems could affect the lender's willingness to proceed or result in a reduced valuation. In some cases, you may be able to negotiate with the seller for repairs or a price reduction. A good surveyor will explain what the findings mean in practical terms.
Yes, but with similar considerations as residential mortgages. You'll typically need at least a 25% deposit for buy-to-let, and fewer lenders operate in this space for non-standard properties. Rental demand for non-standard properties varies - character cottages often let well, while some post-war concrete properties can be harder to fill.
This depends on your priorities. Non-standard properties often offer character, lower prices, or unique features you won't find in standard builds. The trade-offs include more complex mortgages, specialist insurance, and potentially higher maintenance. If you love the property and go in with realistic expectations, non-standard construction can represent good value.
Very few properties are genuinely unmortgageable. The main categories include park homes on rented land, properties with no kitchen or bathroom, those with severe structural defects beyond economical repair, and some unrepaired designated defective construction types. Even challenging situations often have solutions - specialist lenders, bridging finance, or a repair-then-mortgage strategy.
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