After the war Britain needed housing at a speed the traditional trades could not deliver. The answer was systems. Precast reinforced concrete panels, steel frames, factory produced components assembled on site by semi skilled labour. It worked. Hundreds of thousands of homes went up, quickly, and families moved out of prefabs and slums into something with a bathroom.
The definition is broader than most people in the trade assume. Anything outside brick or stone walls with a tile or slate roof can fall into it, and what counts as non-standard construction now covers concrete, steel frame, timber frame, corrugated sheet, felt, fibreglass and a good deal else besides. The commercial consequence is blunt. Deposits on these properties often start at 25% and can reach 40%, and they take roughly 145 days to sell on the open market against about 110 for a conventional house.
1984 is the Year That Still Matters
The reckoning came decades later. Corrosion of steel reinforcement inside precast concrete panels turned out to be a systemic issue across several house types, and the Housing Defects Act 1984 formally designated a list of them as defective.
That legislation did something the industry underestimated at the time. It attached the risk to the system name rather than the individual building. Airey, Cornish Unit, Woolaway, Unity, Wates. A valuer who recognises the type does not need to find a fault, because the type itself is the finding.
Forty years on, an approved repair scheme with a valid certificate will usually satisfy a lender. Without that paperwork the property is frequently cash only, regardless of what condition it is actually in.
The Valuation Problem is Really a Data Problem
Here is what frustrates anyone who has stood in one of these houses and seen sound structure. The decision is rarely made on the structure.
It is made in an underwriting policy written by someone who has never visited, working from a system name, a construction date and a risk table. Evidence changes that outcome. Absence of evidence does not, and the default position when a lender cannot classify something is decline.
Which means the file matters as much as the fabric. For anyone building, refurbishing or holding non-traditional stock, this is the paperwork worth having:
- System identification. The type name in writing, ideally from a structural engineer rather than a local assumption about what these houses are.
- Repair scheme certification. Where a designated defective type has been remediated, the certificate confirming an approved scheme. This is the single document that most often unlocks lending.
- A structural engineer’s report. Current, specific to the property, and stating condition rather than only type.
- Warranty and accreditation for modern systems. For offsite and MMC work, third party assurance covering durability and maintainability. Lenders want a view on the sixty year horizon, not the ten year one.
- Continuous insurance history. Gaps invite questions. An unbroken record quietly answers several of them.
- Photographic and specification records of any works. Concealed remediation that nobody documented is, from a valuer’s perspective, remediation that did not happen.
The Uncomfortable Parallel With MMC
None of this is purely historical, which is why it belongs on a construction site rather than in a property column.
The current push towards modern methods of construction rests on the same underlying proposition as 1948. Build faster, build offsite, use factory precision to solve a housing shortfall that traditional methods cannot address at the required rate. The technology is vastly better. Panelised timber, light gauge steel and volumetric modular are not Airey houses, and the quality control in a controlled factory environment is not comparable to a muddy site in 1950.
But the finance sector does not assess technology. It assesses precedent and documentation. It has been stung once by a national programme of non-traditional housing, and it has a very long institutional memory.
What That Means in Practice
Assurance is not administrative overhead on an MMC project. It is the mechanism that determines whether the finished units are mortgageable, and therefore whether they are worth what the model assumed.
Get the accreditation in place at design stage rather than retrofitting a paper trail once a buyer’s lender has already declined. Keep the system documentation with the property rather than in a project archive that is deleted after seven years. Treat the durability case as a deliverable in its own right.
The post-war programme housed a generation and was, by the standards of the emergency it answered, a considerable success. It also left a category of homes that are difficult to sell three quarters of a century later. Both things are true. The second one is the part worth designing around this time.
