Common Non-Standard Construction Types
Airey houses were designed by Sir Edwin Airey and built by local authorities in large numbers after World War II. They use pre-cast concrete columns and spandrel panels, and are one of the most common non-standard construction types in the UK. Approximately 26,000 were built, primarily in rural areas and small towns. The concrete in older Airey houses can deteriorate over time, and many have been repaired or re-clad. Under the Housing Defects Act 1984 (now consolidated into the Housing Act 1985), Airey houses are classified as defective, and lenders who accept them typically require a PRC certificate confirming the property has been repaired to an approved standard.
Wimpey No-Fines properties use in-situ poured concrete (aggregate and cement without fine sand) in a no-fines technique that creates a cellular structure. Approximately 100,000 were built in the UK. They are generally considered more durable than some other concrete systems, but lenders still apply special assessment criteria.
Timber frame properties are among the most common non-standard types in modern new builds — many contemporary homes (particularly in Scotland, where around 75% of new homes are timber frame) are timber frame — and are generally more widely accepted by lenders than older concrete systems. Steel frame properties are also becoming more common and are similarly assessed. Lenders distinguish between modern timber and steel frame (broadly acceptable) and older or unusual systems (requiring more detailed assessment). Other types include Cornish Units, Reema Hollow Panel, Laing Easiform, Boot, Orlit and many others, each with their own structural characteristics and lender policies.
How Lenders Assess Non-Standard Construction
The primary concern for lenders is whether the property can be insured at full reinstatement value, whether it will retain its value over the loan term and whether it will be saleable if they need to repossess and sell it. Unusual construction types create uncertainty on all three of these factors, which is why lenders apply stricter criteria.
For most non-standard construction types, lenders will require a more detailed structural valuation report from a surveyor experienced with that construction type. In some cases, they will require a full structural survey (RICS Home Survey Level 3, formerly known as a Building Survey) rather than a standard mortgage valuation. For PRC (Precast Reinforced Concrete) properties such as Airey houses, a PRC certificate issued by an approved inspector (such as PRC Homes Ltd, or an RICS surveyor approved under the Housing Defects Act 1984) and confirming the property has been repaired to a recognised standard can significantly improve lender appetite.
Lenders who accept non-standard construction typically offer lower maximum loan-to-value ratios than for standard properties — commonly 70-75% rather than 80-85% — to account for the possibility that the property might be harder to sell or might achieve a lower price than an equivalent standard-construction property. Insurance also tends to be harder and more expensive, and lenders will want evidence of current cover at full reinstatement value.
PRC Certificates and Repair Programmes
For precast reinforced concrete properties, a PRC certificate is the key document that unlocks mainstream lending. These certificates are issued by PRC Homes Ltd or other approved bodies and confirm that a property has been repaired or upgraded to a recognised standard that addresses the structural concerns associated with the original construction. Without a PRC certificate, many lenders will not consider a concrete system-built property at all.
PRC repair programmes typically involve overlaying or replacing the original concrete structure with a new brick or block outer skin, improving insulation and upgrading services. The cost of a PRC repair is substantial — commonly £15,000 to £30,000 — but significantly increases the property’s marketability and value. Some specialist lenders will fund a PRC repair programme through a secured loan, with the certificate being provided on completion of the works.
If you own a PRC property without a certificate and want to raise finance, it may be worth investigating whether the cost of completing a recognised repair programme (funded by other means if necessary) would be worthwhile to open up a wider range of lenders and achieve a better loan rate. The typical rate differential between a PRC-certified and non-certified case is 1.5-3.0 per cent on APRC, which over a typical 10-15 year loan often more than pays for the cost of the repair programme.
