Common Non-Standard Construction Types and Their Mortgage Status
Timber Frame Construction
Modern timber frame - which is now one of the most common construction methods for new build properties - is accepted by the majority of mortgage lenders without restriction. Older timber frame construction (pre-1960s, particularly in rural areas) may require additional survey evidence. Traditional half-timbered or oak frame construction is specialist territory.
Concrete and Prefabricated Construction
Various post-war prefabricated concrete construction systems - including BISF (British Iron and Steel Federation), Airey, Cornish Unit, Wates, and Reema - are designated as 'defective' under the Housing Defects Act 1984 and are refused by most standard lenders. Specialist lenders will consider these properties, typically at lower LTVs (maximum 70-75%), where a structural survey confirms the property is in sound condition and any necessary PRC (Precast Reinforced Concrete) certificate is available.
Steel Frame Construction
Steel-framed properties - common in certain post-war housing developments - are accepted by a limited panel of specialist lenders. Survey requirements are stringent, and maximum LTV is typically 75%. Properties that have been appropriately refurbished and re-clad are more readily mortgageable than those in original condition.
Thatched Properties
Thatched roofs are accepted by a number of specialist building societies and lenders who understand rural properties. The primary considerations are: the age and condition of the thatch, the insurance situation (thatched property insurance is specialist and expensive), and the property's compliance with current fire safety standards.
Single-Skin Brick
Single-skin brick construction - common in some pre-1920s terraced properties - is accepted by specialist lenders with appropriate survey evidence confirming structural integrity and moisture management.
Survey Requirements for Non-Standard Construction
All non-standard construction properties require a minimum RICS Level 3 Building Survey (full structural survey) for mortgage purposes. For designated defective concrete types, a specialist structural engineer's report may also be required. The cost of these surveys should be factored into purchasing budgets.
PRC Certificates and Cossor/BRE Certificates
Properties of designated defective PRC construction that have been reprofiled with an approved repair system (typically involving concrete reinforcement and reclad) may hold a PRC Certificate confirming the repairs meet recognised standards. This certificate significantly improves mortgage options for these properties - some standard lenders will accept certificated PRC properties.