Module 2 · Buildings & Moisture Basics
2.4 Floors & Moisture Behaviour
7 min read
Floors are the least inspected part of most surveys and a disproportionate source of trouble. They sit directly on damp ground, they hide services, and their failures show up somewhere else — usually as damp at the base of a wall, where they get confidently attributed to rising damp.
Learning objectives
By the end of this lesson you will be able to:
- Describe how suspended timber and solid concrete floors each manage ground moisture.
- Explain why subfloor ventilation is a structural requirement, not a nicety.
- Recognise the signs of a failed or bridged damp-proof membrane.
- Distinguish floor-related damp from damp rising through a wall.
Key terms
- Suspended timber floor
- Floor boards on joists spanning over a ventilated void, holding the timber clear of the ground.
- Subfloor void
- The ventilated space beneath a suspended floor, kept dry by cross-flow air through air bricks.
- Air brick
- A perforated brick admitting air to the subfloor void. Blocking one starts a slow disaster.
- Screed
- The levelling layer over a concrete slab, often containing pipework and underfloor heating.
Free — enrol to continue
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.