What is a damp proof course (DPC)?

A damp proof course (DPC) is a horizontal layer of impermeable material, usually bitumen, plastic, or slate, installed near the base of a building's walls to stop moisture from rising up through the masonry. In older Cheltenham properties, this line often sits around 150mm above the external ground level, though modern builds may place it differently depending on site conditions and building regulations.

When paving or surfacing is laid against a building, the height matters critically. If paving is built up above the DPC line, water can bridge across it, essentially bypassing the barrier and allowing damp to penetrate the wall. This leads to rising damp problems inside: discolored plaster, salt stains, deteriorating render, and structural dampness that affects the property's integrity and comfort.

The standard practice is to lay all paving, hardstanding, and gravel at least 150mm below the DPC line, ensuring the protective layer remains unbroken and effective. If you are planning patio installation or groundworks, the contractor must measure the DPC height on your property and set the finished level accordingly. Checking this detail at the start prevents costly remedial work later and protects your home from damp problems that are difficult and expensive to fix.