What is a Damp Proof Course and Do I Need One?

In the realm of building and construction, a damp proof course (DPC) is an essential feature that acts as a long-term moisture barrier, preventing moisture from rising up through the walls of a building. This process, known as rising damp, can cause significant damage to structures if left unchecked. A DPC is typically installed at the base of walls, just above ground level, and is a critical component in the preservation of both the integrity and the aesthetic appeal of a property.

The Importance of Damp Proof Courses

The primary purpose of a damp-proof course is to stop ground moisture from rising up through the capillaries in bricks and mortar, a phenomenon akin to how a sponge soaks up water. Without a DPC, this moisture can ascend walls, leading to damp patches, peeling paint or wallpaper, and in more severe cases, the deterioration of plaster and masonry. Such conditions not only detract from the appearance of a building but can also foster the growth of mould and mildew, contributing to unhealthy indoor environments.

Moreover, the presence of dampness within walls can significantly reduce the thermal efficiency of a building. Moisture-laden walls conduct heat more readily than dry walls, leading to increased heating costs and energy inefficiency. Thus, a well-maintained damp proof course is not only crucial for the structural health of a building but also for the comfort and well-being of its occupants.

  • Moisture Barrier: A DPC acts as a critical barrier against ground moisture, preventing it from rising through the walls—a process known as rising damp.
    • Prevents Structural Damage: By stopping moisture, a DPC helps prevent the deterioration of plaster, masonry, and other building materials.
    • Aesthetic Preservation: It maintains the appearance of a building by preventing damp patches, peeling paint, and wallpaper damage.
    • Health Benefits: A dry environment discourages the growth of mould and mildew, contributing to healthier indoor air quality.
    • Energy Efficiency: Dry walls are more thermally efficient, reducing heat loss and leading to lower heating costs.
    • Long-term Savings: By protecting the structural integrity of a building and improving energy efficiency, a DPC can lead to significant long-term savings.

The Degradation of Insulation Over Time

Insulation within walls plays a vital role in maintaining a building’s temperature, keeping it warm in the winter and cool in the summer. However, over time, if moisture penetrates the insulation, it can settle at the bottom of the wall cavity. This accumulation of moisture can lead to several problems, including the compression and degradation of the insulation material. As the insulation’s effectiveness is compromised, its ability to prevent heat transfer diminishes, leading to increased energy consumption and higher bills.

Moreover, the presence of moisture in wall cavities creates an ideal breeding ground for mould and mildew. These fungi can spread to the interior of the house, posing health risks to residents, particularly those with respiratory issues. The detection of mould often necessitates not only the treatment of the affected area but also an investigation into the cause of the dampness, underscoring the importance of a fully functional DPC.

Removing and Re-Creating a Damp Proof Course

Over time, a damp proof course can become compromised due to physical damage, bridging (where raised external ground or internal floor levels bypass the DPC), or simply the degradation of the material used in the DPC. When this occurs, it may become necessary to remove and replace the DPC to ensure the continued protection of the building from rising damp.

The process of replacing a damp proof course involves several steps, often beginning with the diagnosis of the problem by a professional. Once the need for replacement is confirmed, the old DPC material is removed. This can involve significant work, including the temporary removal of brickwork or the drilling of holes in walls for the injection of a new DPC. The choice of method depends on the construction of the building and the extent of the damp problem.

Modern techniques for creating a new DPC include the injection of water-repellent chemicals into the walls, which form a barrier against moisture. Another method involves the installation of a physical membrane that acts as a barrier to water. Regardless of the method, the goal is to establish a continuous barrier that prevents moisture from rising up through the walls.


A damp proof course is a crucial element in the construction and maintenance of buildings, acting as a defensive barrier against the ingress of ground moisture. Without a functioning DPC, buildings are susceptible to rising damp, which can lead to structural damage, decreased thermal efficiency, and the proliferation of unhealthy mould and mildew. Over time, it may become necessary to replace a DPC, a task that requires professional expertise to ensure the long-term protection of the property. By understanding the importance of a damp proof course and the potential consequences of its failure, property owners can take proactive steps to safeguard their investments and ensure a healthy living environment.