Damp Proofing

Damp ProofingDamp proofing is a type of waterproofing applied to building foundation walls to prevent moisture from passing through the walls into interior cavities.

A damp-proof course (often abbreviated to DPC) is a horizontal barrier in a wall designed to resist moisture rising through the structure by capillary action - a phenomenon known as rising damp. A damp-proof membrane (DPM) performs a similar function for a solid floor. Due to capillary movement of water, water rises from earth to the building passing through foundation as it rises higher to reach walls. Rising water in walls may damage them by creating cracks, breaking cement-paint bonds and creating dark-spots on wall etc. So, to avoid water from reaching to wall level a DPC layer is injected at plinth level (the joint level of walls and foundations). A DPC layer is usually laid below all the walls unaffected from the issue that the respective wall is a load bearing wall or a partition wall. Usually, DPC membrane is normally 4" to 9" wide.

Rising damp can occur for various reasons - the failure of an existing damp proof course, bridging due to the raising of external ground or internal floor levels, or in older buildings, the complete absence of a damp proof course.

Brick, stone and mortar are porous allowing damp from the ground to rise by capillary action, carrying with it ground salts including chlorides and nitrates. These salts from the ground can absorb moisture from the atmosphere leading to wall dampness in conditions of high relative humidity. Also they can ruin decorations and break down internal plaster. In older days, stone-slab was mostly used as DPC material.Damp Proofing Drilling Pattern

Building standards in many countries require most new buildings to incorporate a DPC/DPM at the time of construction.

NCDP employ the following methods to remedy rising damp:

  • Removal of all contaminated render and plaster
  • Injection of all solid walls at ground level with suitable chemical damp proof barrier(DPC)
  • Application of tanking on any areas where required.

Following the DPC injection process the plaster may be reinstated incorporating a salt inhibitor to prevent contaminated salts accumulating and attacking new décor and plaster.