"Non-standard construction" covers everything from a modern timber-frame new-build to a post-war concrete prefab, and lenders treat these two ends of that spectrum completely differently. This guide separates the construction types that are genuinely mainstream from the ones that carry real structural risk, covers the specific certificate that decides whether a property is mortgageable at all, and the practical steps that widen your lender pool.
Figures below reflect published 2026 specialist mortgage broker and surveying guidance, current to mid-2026. This is general information, not financial or surveying advice; a specific property's construction and repair history should be assessed by a qualified surveyor or structural engineer.
- The fear that's overblown: modern timber frame
- The real risk: post-war concrete construction
- The PRC certificate that decides mortgageability
- Other non-standard types, and how much they actually matter
- Lender tiers, and the deposit lever
- Why a structural engineer beats a standard survey here
- Frequently asked questions
1. The fear that's overblown: modern timber frame
Modern timber frame properties, built to current building regulations and covered by an approved structural warranty, are now widely accepted by mainstream lenders without any special difficulty. It's specifically older timber frame properties, or those in poor condition, showing signs of rot or insect damage, that face a genuinely more limited lender pool. If you're looking at a recently built timber-frame home with a valid NHBC or equivalent warranty, the construction type alone is unlikely to be a meaningful obstacle to a mortgage.
2. The real risk: post-war concrete construction
Precast Reinforced Concrete (PRC) houses were built in large numbers during the 1940s and 1950s using precast concrete panels, a fast, cheap solution to the acute post-war housing shortage that didn't depend on bricklayers. Many were originally designed to last just 10 to 30 years; a significant number are still standing more than 70 years later. Over time, the steel reinforcement inside the concrete can corrode and expand, a process often called "concrete cancer," causing the surrounding concrete to crack. Several well-known PRC designs, including Airey, Reema, Cornish, Orlit, Wates, and Wimpey No-Fines types, along with steel-framed BISF houses, were formally designated as defective under the Housing Defects Act 1984.
3. The PRC certificate that decides mortgageability
Most mainstream lenders will almost universally refuse a mortgage on a PRC property without a PRC certificate (sometimes called a Certificate of Structural Adequacy) confirming the property has undergone approved structural repairs, typically removing or encasing the original concrete panels and replacing them with traditional brick and block cavity wall construction. Without this certificate in place, the property may be effectively unmortgageable through mainstream channels, which is precisely why PRC properties without one tend to sell considerably below the price of an equivalent standard-construction home in the same area.
4. Other non-standard types, and how much they actually matter
A frequently underestimated point: the rate differential for well-understood, widely-accepted non-standard types, timber frame, stone, and ordinary flat roofs among them, is often smaller than buyers and investors expect. The genuinely large gap in both rate and lender availability opens up specifically around the higher-risk, structurally-uncertain categories covered above, not non-standard construction as a blanket category.
5. Lender tiers, and the deposit lever
Mainstream high-street lenders generally decline unrepaired PRC and other designated-defective construction types outright. A tier of specialist lenders will consider more complex cases, including ex-Designated Defective homes that have since been properly repaired and certified, but typically only through a mortgage broker, and usually at a rate premium over a standard-construction equivalent. A larger deposit, in the region of 25% to 35%, opens up considerably more lender options than a 10% to 15% deposit would, since it reduces the lender's exposure on a property they may still regard as harder to resell than a conventional home.
6. Why a structural engineer beats a standard survey here
For any non-standard property with a known or suspected structural risk, a report from a chartered structural engineer is generally considered more valuable than a standard Level 3 RICS building survey, since it specifically interrogates the structural integrity in a depth a general survey isn't designed to match. Identifying the exact construction type, and any prior repair history and certification, before applying for a mortgage is genuinely worth doing upfront, since it directly determines which lenders, if any, will even consider the application.
7. Frequently asked questions
Is it hard to get a mortgage on a timber frame house?
Not usually. Modern timber frame properties built to current building regulations and covered by an approved structural warranty are now widely accepted by most mainstream lenders without any special difficulty. It's specifically older timber frame properties, or those in poor condition, that face a more limited pool of willing lenders.
What is a PRC certificate and why do I need one?
A PRC (Precast Reinforced Concrete) certificate, sometimes called a Certificate of Structural Adequacy, confirms that a post-war concrete-panel property has undergone approved structural repairs, typically removing or encasing the original concrete and replacing it with traditional brick and block construction. Most mainstream lenders will almost universally refuse a mortgage on a PRC property without this certificate.
Do I need a bigger deposit for a non-standard construction property?
Often, yes, though it depends on the specific construction type. A larger deposit, in the region of 25% to 35%, opens up significantly more lender options than a 10% to 15% deposit would, since it reduces the amount a lender is exposed to on a property they may consider harder to resell.
Is a standard survey enough for a non-standard construction property?
Often not. For properties with known or suspected structural risk, such as older concrete construction, a report from a chartered structural engineer is generally considered more valuable than a standard Level 3 RICS survey, since it specifically assesses the structural integrity a standard survey isn't designed to interrogate in the same depth.
Continue your research
About the author
✓ Editorially reviewed — all Poqet guides are checked for factual accuracy before publication and updated when UK rates or legislation change. Editorial Policy