Non-Standard Construction Mortgages: Which Lenders Will Lend on Unusual Builds

What "non-standard construction" means

A standard construction home in the UK is a brick or block built house with a tiled or slate pitched roof. Lenders treat this as the baseline and most mortgages assume it. Anything else is "non-standard" and triggers additional scrutiny.

Common non-standard categories include:

• Concrete construction: precast concrete panels (PRC), in-situ concrete frame, BISF steel-framed houses, Wimpey No-Fines, Smith houses, Cornish Unit, Reema, Airey, Unity, Wates
• Timber frame: although modern timber frame is now mainstream, older timber frame (pre-1980s) is sometimes flagged
• Steel frame: BISF, Hawksley, and similar 1940s to 1960s steel frame homes
• Solid stone or cob: traditional construction in rural Devon, Cornwall, the Lake District
• Thatched roofs: not strictly construction but often grouped with non-standard
• Flat roofs: especially over the main living area
• High-rise leasehold flats: often face additional scrutiny because of cladding, EWS1 forms, and building safety

Some of these are riskier than others. Modern timber frame is essentially mainstream now and most lenders accept it without issue. Pre-1960s precast concrete is at the other end of the spectrum and many lenders will refuse to lend on certain types regardless of condition.

Why lenders care

Lenders are pricing two risks: the cost of repair if the property deteriorates, and the resale market if they need to repossess and sell. Non-standard constructions tend to have higher repair costs (specialist contractors, harder-to-source materials) and a smaller resale market (other buyers face the same mortgage difficulty), so the lender's recovery in a default scenario is worse.

Some construction types have specific known defects. The Housing Defects Act 1984 designated certain prefabricated reinforced concrete (PRC) house types as defective, and most lenders will not lend on a Designated Defective home unless the structural panels have been replaced under a recognised scheme such as PRC Homes Limited.

Which lenders will consider non-standard

The lender appetite varies dramatically:

• High street banks (Halifax, Nationwide, Santander, Barclays, NatWest, HSBC) have the strictest criteria. They generally accept modern timber frame and modern non-traditional builds with full structural reports. They generally refuse 1940s to 1960s PRC, BISF, and similar.
• Building societies (Skipton, Yorkshire, Coventry, Leeds, Principality) are often more flexible. Some specialise in non-standard properties and will lend on construction types the high street will not touch, sometimes at slightly higher rates.
• Specialist lenders (Vida, Bluestone, Foundation, Pepper Money) lend on the most challenging cases, including ex-Designated Defective homes that have been repaired, and properties with known issues. Rates are higher and broker access only.

For any non-standard purchase, a mortgage broker who specialises in non-standard property is essential. The advice is worth more than the fee.

How to improve your application

1. Get a full structural engineer's report before applying. A clear report from a chartered structural engineer (CEng MIStructE) is worth more than a Level 3 RICS survey for a non-standard property.

2. Identify the exact construction type and any repair history. PRC homes that have been repaired under a Designated Defective scheme carry a Certificate of Structural Adequacy that lenders accept.

3. Bring a larger deposit. 25% to 35% deposits open up significantly more lender options than 10% to 15%.

4. Use a broker familiar with non-standard property. Generic comparison sites do not show the lender appetite for unusual builds.

5. Be ready for valuation conditions. The lender may require specific repairs or guarantees as a condition of the offer.

How to spot non-standard construction before viewing

Property Passport UK shows the EPC property type and construction age band for every property in England and Wales, sourced directly from the EPC Register. Search the address at [/search](/search) to see the property type, construction age, wall type description, and any other clues that flag a non-standard build before you commission a survey or pay for a valuation.

Check the property on Property Passport UK before you buy

Property Passport UK aggregates verified data on every one of the 19.35 million properties in England and Wales, including listed building status, conservation area, EPC, flood risk, and HM Land Registry tenure. Search any address at [/search](/search) before you make an offer or commission a survey. Construction-related risks often flag through one of these data points before they show up in the building survey itself.

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