DPC's

The installation of the damp-proof courses in a cavity wall construction is an important element in ensuring the building performs to a satisfactory level. Detailed below are installation details in areas where there is a high risk of water ingress.

Frames must be installed behind the outer leaf and care should be taken to ensure frames are installed plumb, level, square, and fitted to acceptable tolerances.

To ensure dampness cannot penetrate inside the building it is important to ensure that the DPC is provided in the correct location.

Provide stepped DPCs to all openings in cavity walls or proprietary cavity tray DPCs.

Weepholes should be provided above openings at a maximum of 450 mm centres.

In the case of brick, fairfaced blockwork, or any surface where the outer leaf is unrendered, weepholes should be provided at no more than 450 mm centres. Also, lodging of mortar droppings in DPC should be avoided.

Careful detailing of damp-proof courses and flashings is required for flat roof and mono-pitch roof abutments. These types of abutments can occur at balconies, porches, garages etc. In all cases, cover flashings should be built-in under the stepped DPC.

Metal used for flashings should be non-ferrous. In cases where lead is used, the lead should be at least a code four (colour code blue). Laps for flashings should be greater than 100 mm (150 mm in locations prone to high wind and rain) and individual lengths should be less than 1.5 m.

If DPC is not installed correctly, any moisture that drains down the cavity will seep through and show up as damp on the ceiling of habitable rooms inside.