Module 3 · Types of Damp in Detail
3.6 Bridging: External & Internal
7 min read
Bridging is the single most under-recognised mechanism in UK damp surveying. The barrier is intact and doing its job; the water simply goes around it. Recognising a bridge often converts a four-figure remedial quote into an afternoon with a spade, which makes it one of the most valuable things you can spot.
Learning objectives
By the end of this lesson you will be able to:
- Define bridging and explain why it defeats an intact barrier.
- Identify the common external and internal bridges.
- Distinguish a bridged DPC from a failed one.
- Explain why bridging is so often reported as rising damp.
Key terms
- Bridging
- A continuous moisture path around a barrier that is itself intact and functioning.
- External bridge
- Raised ground, render or debris outside the wall carrying moisture over the DPC line.
- Internal bridge
- Plaster, screed or a later floor inside the building carrying moisture across the DPC from below.
- Cavity bridge
- Mortar, debris or saturated insulation carrying water across the cavity to the inner leaf.
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Read the rest of Types of Damp in Detail
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.