DPC and Cavity Tray Locations

150 mm

Damp-proof courses (DPCs) must be installed at the base of walls, at least 150mm above the external ground level, and linked to the damp-proof membrane (DPM) in solid floors to prevent rising damp

Every figure for this topic is on one page: Cavity trays and DPC: where are they needed and how high?

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Damp-proof courses (DPCs) must be installed at the base of walls, at least 150mm above the external ground level, and linked to the damp-proof membrane (DPM) in solid floors to prevent rising damp. Cavity trays are essential over all openings within a cavity wall, such as windows, doors, and air bricks, to collect and discharge water that penetrates the outer leaf.

Basis in regulation

BS 8000-3
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Part C
Approved Document C
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How to check it on site

Verify DPCs are correctly positioned at least 150mm above ground level and linked to the DPM, and that cavity trays are installed above all cavity interruptions.

Common failure

DPCs are often installed too low, or cavity trays are omitted or incorrectly installed, leading to damp penetration above openings.

Last updated 23 August 2026. This is our editorial summary of publicly available regulation, not building control approval or a warranty determination.

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