Damp Proof Course (DPC) and weep hole details
What it looks like
Disrupted DPCs or blocked/missing weep holes can lead to moisture accumulation within the cavity or rising damp.
Why it happens
A Damp Proof Course (DPC) is an impermeable layer installed horizontally in walls to prevent moisture rising from the ground or penetrating from below. Weep holes are small openings in the outer leaf of a cavity wall, typically positioned above a DPC or cavity tray, to allow trapped water to drain out. These elements are crucial for maintaining a dry building envelope.
What it costs if it is missed
A Damp Proof Course (DPC) is an impermeable layer installed horizontally in walls to prevent moisture rising from the ground or penetrating from below. Weep holes are small openings in the outer leaf of a cavity wall, typically positioned above a DPC or cavity tray, to allow trapped water to drain out. These elements are crucial for maintaining a dry building envelope.
How to inspect for it
Confirm that the DPC is continuous and correctly lapped, and that weep holes are installed at appropriate spacing and height above the DPC or cavity tray.
How to prevent it
A Damp Proof Course (DPC) is an impermeable layer installed horizontally in walls to prevent moisture rising from the ground or penetrating from below. Weep holes are small openings in the outer leaf of a cavity wall, typically positioned above a DPC or cavity tray, to allow trapped water to drain out. These elements are crucial for maintaining a dry building envelope.
Basis in regulation
Last updated 23 August 2026. This is our editorial summary of publicly available regulation and site practice, not building control approval or a warranty determination.