What is Damp Proof Course?

Many things go into property construction, but damp-proof course (DPC) is arguably one of the most underrated. It’s something most people never have to worry about, and yet it is such a crucial part of ensuring a building remains strong throughout its lifetime.

From new garages to multi-story office blocks, damp proof course is a vital part of any building construction. This comprehensive guide provides all you need to know about DPC, whether you’re new to the trade or an experienced professional.

What is Damp Proof Course?

Often shortened to DPC, damp proof course is a strip of sheeting, often plastic, which is used to create a barrier between a building’s walls and the ground.

DPC plays a crucial role in protecting a building’s walls from external moisture. Without DPC, walls would suffer from rising damp, a common and costly issue in older and poorly managed properties.

DPC and damp proof membranes (DPM) are often conflated, as both work together to damp-proof a building. Technically, DPMs are broad sheets used to protect the foundations of a property, while DPC is narrower and specifically designed for use within walls.

How Does Damp Proof Course Work?

Damp proof course works by creating a barrier that stops water from travelling up the walls of a building, a phenomenon known as capillary action.

Have you ever noticed how water travels up a sponge or tissue, against the pull of gravity? This is an example of capillary action, a scientific phenomenon where liquid is pulled up through small, narrow spaces via a combination of surface tension and adhesive forces.

Capillary action causes water to rise through most porous materials, from household sponges all the way to the mortar and cement used in building construction. Without any protection, capillary action means that water in the Earth would eventually rise through concrete foundations and brick walls – this is what causes rising damp.

Modern damp proof course is usually made of recycled polyethylene, a very common plastic used for making packaging such as bottles. Not only is this material waterproof, but it’s also very resistant to degradation, which means DPC can protect buildings for an incredibly long time.

Why Damp Proof Course is Crucial for Properties

Without damp proof course, most masonry buildings would be at risk of rising damp, which often presents as tide marks at the bottom of walls. Rising damp presents a host of issues, including:

Stained and damaged walls, including peeling paint or wallpaper
Increased mould growth
Structural damage to the building

Because it quickly solves many of these problems, damp proof course was made a requirement for all property builds in 1875. Initially, damp proof courses were made from materials such as iron, slate and lead, before plastic became the go-to choice.

Can You Replace a Damp Proof Course?

While all properties should have a damp-proof course, problems with bad installation sometimes mean it fails and needs to be replaced.

There are two main ways in which DPC is replaced or inserted into existing buildings:

Pumping a liquid DPC into the wall
Installing a new plastic sheet

Liquid DPC is by far the most common solution, as it is cheaper and less intrusive for the building. Often, it involves pumping a chemical solution into a series of holes drilled into the wall. The liquid DPC is then absorbed like water before hardening, creating a new barrier to stop water from rising through.

Installing a physical DPC in an existing building is a much more arduous and expensive task, as it involves removing a whole line of mortar and sometimes bricks, also. However, when done right, it can offer longer damp protection than a liquid solution, which is typically guaranteed for around ten years.

How Much Does Damp Proof Course Cost?

Because DPC is such a simple material, it often doesn’t cost too much. However, getting it professionally fitted or repaired can be expensive, as it takes skill and experience to ensure the barrier it creates is impenetrable.

Liquid DPC injections tend to cost around £2,000, based on an average property size and accounting for other parts of the process, including decorating finishes. Meanwhile, having a DPC sheet retrofitted can cost double that depending on the size and nature of the building.

If you’re looking to pick up a great deal on damp-proof course, check out the range available here at Fastbuild. With quality products available at great trade prices, Fastbuild is the perfect place to get everything you need for your next job.