Damp proofing

Moisture resistance is not necessarily absolute; it is usually stated in terms of acceptable limits based on engineering tolerances and a specific test method.

Damp proofing is accomplished several ways including: Materials widely used for damp proofing include:[6] A DPC is a durable, impermeable material such as slate, felt paper, metal, plastic or special engineered bricks[7] bedded into the mortar between two courses of bricks or blocks.

This method requires weep vents to enable water to drain from the cavity, otherwise dampness could rise from above the DPC.

Until the 20th century, masonry buildings in Europe and North America were generally constructed from highly permeable materials such as stone and lime-based mortars and renders covered with soft water-based paints which all allowed any damp to diffuse into the air without damage.

In older buildings, damp stains on internal walls are usually due to external factors such as: Some DPC materials may contain asbestos fibres.