Module 2 · Buildings and How They Handle Moisture
2.1 Every Building Has a Moisture Strategy
8 min read
Damp training usually presents construction as a catalogue: here is a solid wall and its problems, here is a cavity wall and its problems. That produces surveyors who can recognise a defect they have seen before and are lost in front of one they have not. The alternative is to ask what each construction was designed to do with water, because there are only three answers, and every failure is one of those three strategies being defeated.
Learning objectives
By the end of this lesson you will be able to:
- Name the three moisture strategies in British housing and the era each belongs to.
- Identify which strategy a building uses from its construction, not its age alone.
- Predict the characteristic failure mode of each strategy before inspecting.
- Recognise when a building has been converted from one strategy to another — the most dangerous case.
Key terms
- Absorb-and-release
- The solid-wall strategy: the wall takes up driving rain and gives it back by evaporation. Tolerates being wet; fails when evaporation is blocked.
- Separate-and-drain
- The cavity strategy: the outer leaf gets wet, the cavity interrupts the path, and water drains out through weeps. Fails when the cavity is bridged.
- Exclude-entirely
- The timber-frame and modern strategy: a defined barrier keeps water off a structure that cannot tolerate it. Fails at penetrations and laps, not across areas.
- Strategy conversion
- Altering a building so it no longer uses the strategy it was built around — filling a cavity, rendering a solid wall, insulating internally.
Read the rest of Buildings and How They Handle Moisture
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