Common System-Built Types and Their Mortgage Status
Laing Easiform is one of the most widely encountered system-built types, using in-situ poured concrete with a rough-cast render finish. It was not designated under the Housing Defects Act 1984, and some lenders will consider it on the basis of a satisfactory structural survey — making it somewhat easier to remortgage than formally designated PRC types. However, the quality of the original construction and the maintenance history of the specific property remain important factors.
The Cornish Unit and Airey house are designated PRC types, meaning that PRC certification following an approved repair scheme is generally required before lenders will consider them. The BISF (British Iron and Steel Federation) house uses a steel frame and presents challenges around potential corrosion rather than concrete carbonation. Each type has its own specific structural concerns and its own subset of lenders who understand and will consider it.
Other system-built types include the Reema Hollow Panel, the Orlit house, the Unity type, the Tarran prefab, and various regional variants. The key is to identify the specific type accurately — different types have different repair and certification histories, and a surveyor or broker who misidentifies the type can lead you down an entirely wrong path. An accurate identification is the essential starting point for any system-built remortgage enquiry.
Valuation Challenges for System-Built Properties
Valuing a system-built house presents specific challenges for mortgage lenders and their appointed valuers. The primary issue is the limited availability of comparable sales evidence. In areas where system-built houses are common — such as post-war council estates — comparables may be available among similar properties, but they are often discounted relative to standard construction in the same area, reflecting the limited mortgage market.
A further valuation challenge arises where a system-built house has been repaired or refurbished. The surveyor must assess whether the repair adds value commensurate with its cost, and whether the repaired property is genuinely equivalent to a standard construction house from a marketability perspective. In many cases, repaired system-built houses are valued at a modest discount to standard construction, even after full PRC certification, because the pool of potential buyers remains smaller.
For remortgage purposes, the RICS Level 3 structural survey and the mortgage valuation are separate exercises, but both must be satisfactory for the lender to proceed. Where the structural survey raises concerns, the valuation is often affected — either through a reduction in value or through conditions attached to the valuation requiring remedial works before the mortgage can proceed.
