Module 2 · Buildings and How They Handle Moisture
2.6 System-Built and Non-Traditional Housing
8 min read
Britain built well over a million non-traditional homes in the post-war decades, across dozens of named systems. Their moisture behaviour is not a variation on masonry — carbonation in precast concrete, interstitial condensation in no-fines, cold bridging and corrosion in steel frame are type-specific mechanisms with type-specific evidence. For these buildings, identifying the system is not context for the survey; it is the first diagnostic step, and getting it wrong invalidates everything after.
Learning objectives
By the end of this lesson you will be able to:
- Recognise the major non-traditional families from visible evidence.
- State the characteristic moisture and durability mechanism of each family.
- Explain why designation as defective under the Housing Defects legislation matters to a survey.
- Know when to stop and recommend a specialist structural appraisal.
Key terms
- No-fines concrete
- Concrete cast without fine aggregate, giving an open-pored monolithic wall. Drains rather than absorbs, and depends completely on its render for weathering.
- PRC (precast reinforced concrete)
- Panel and post systems assembled from factory-cast units. Many named types were designated defective under the Housing Defects Act 1984.
- Carbonation
- Atmospheric CO2 reacting with concrete over decades, reducing its alkalinity so embedded steel is no longer passivated and begins to corrode.
- Designated defective
- A statutory designation of specific system types as inherently defective, with consequences for mortgageability and for the assistance available to owners.
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