Module 2 · Buildings & Moisture Basics
2.3 Solid Walls, Cavity Walls & Timber
8 min read
Walls are where most damp shows up, and the three main constructions fail in completely different ways. Knowing which one you are looking at — and being able to check rather than assume — narrows a diagnosis faster than any instrument.
Learning objectives
By the end of this lesson you will be able to:
- Distinguish solid, cavity and timber-framed walls from what is visible on site.
- Explain how each type manages water and how each type fails.
- Describe cavity bridging and why it is so frequently the real answer.
- Recognise the moisture thresholds at which timber begins to decay.
Key terms
- Cavity
- The deliberate gap between the outer and inner leaves of a wall. Its emptiness is the point — it breaks the path for liquid water.
- Wall tie
- Metal connector holding the two leaves together across the cavity.
- Bridging
- Anything giving moisture a continuous path it was designed not to have — across a cavity, or around a DPC.
- Cavity tray
- A membrane inside the cavity that catches water and directs it back out through weep holes, usually above openings.
- Wet rot / dry rot
- Fungal decay of timber. Wet rot needs sustained high moisture; dry rot can spread through masonry to drier timber nearby.
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Read the rest of Buildings & Moisture Basics
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.