Module 6 · Retrofit and Moisture Risk
6.2 BS 5250 as Integrated Moisture Management
8 min read
For decades the guidance on moisture in buildings was framed around condensation: predict it, ventilate against it, and specify a vapour barrier. The 2021 revision of BS 5250 reframed the subject as management of moisture from all sources across the whole building, over time. That is not a presentational change — it alters what you assess, and practitioners still working from the older framing make a predictable set of errors.
Learning objectives
By the end of this lesson you will be able to:
- State what the integrated approach covers that condensation control did not.
- Identify all the moisture sources a building has to manage.
- Explain why drying capacity matters as much as moisture exclusion.
- Recognise errors that come from the older condensation-only framing.
Key terms
- Integrated moisture management
- Considering all moisture sources, all transport mechanisms and the building's capacity to dry, as one system rather than as separate problems.
- Moisture balance
- Whether the moisture entering a construction over a period is matched by the moisture leaving it. A construction can tolerate wetting if it dries faster than it wets.
- Construction moisture
- Water built into a structure — in mortar, screed, plaster and wet trades — which must leave before the building reaches equilibrium.
- Drying capacity
- How fast a construction can release moisture. Reduced by impermeable layers on either side, and by the absence of ventilation to a void.
Read the rest of Retrofit and Moisture Risk
Module 1 is open to everyone. The remaining six modules — building science, each damp mechanism in depth, meters and thermal imaging, the full inspection method, and report writing — are free too. We just ask for an email so you can pick up where you left off, and so we can send your certificate when you finish.