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See also Damp proofing tips >

Damp can be a serious problem in all building and construction, especially older houses in temperate climates. Here we look at the basic types.

Dampness in homes or damp basements are a common problem, and can be of different types. If you need to protect the walls of your house or basement or any building, you might want to consider damp proofing. Damp proofing is a protective measure applied to the exterior of building foundation walls. It is made by giving the wall a horizontal barrier to prevent moisture rising through the structure. This is also known as damp proof course, DPC.

Nowadays, almost every building incorporates DPC when it is being constructed. This can be in the form of thin plastic sheet, bricks, or a layer of bitumen. When DPC is not applicable, building constructors will think of some ways to replace the DPCs such as drilling holes into the walls at regular intervals to inject penetrating chemicals as silicone. For walls that can't be drilled for a chemical DPC, an osmotic electrical system is used instead. See later.

The commonly known DPC is formed by a thick plastic strip bedded into the mortar between two courses of bricks or blocks. DPC is also used to avoid mould from growing. Most people think mould will grow in liquid. Actually, it just needs some humidity level around 65% - 99%. But we also require some humidity in our homes so a completely dry environment is not a good idea.


Above: Damp proof course DPC in new build

The most common type of damp is rising damp, which occurs when moisture from the ground works its way up the walls of a home. This is helped by porous masonry.

The water doesn't travel alone, and often brings chloride, nitrate and salts with it, which cause internal walls and decorations to become stained and ugly.

Timber decay is also a direct result of damp, in a home where timber products are unprotected, and kept in contact with the masonry.

Build up of mould and fungal deposits caused by damp could also pose a threat to the health of the family. The only consolation to rising damp is that it is only possible for it to rise to one meter above ground level, as capillary action cannot possibly lift the moisture any higher.

Dry rot fungus is a slow killer, and works its way like a cancer, eating away through masonry, and also destroying any timber that falls in its path.

Wet rot when compared with Dry Rot is not as big a problem. This is basically the process of timber decaying naturally due to high levels of moist air in homes. This type of damp is normally caused due to a basic structural fault, like a timber product placed adjacent to a damp wall.

Most homes are equipped with damp proofing, a physical material inserted into the fabric of the building structure, either horizontally or vertically. It works as an obstacle, stopping water from passing to the levels above and walls within the home.

This damp proofing could either become ineffective over time in old buildings, or the porous stone could become porous again after a few years.


There are both simple as well as tough remedies to get rid of damp.

When dealing with damp on your own, one must resort to simple techniques, such as installing a dehumidifier at home, and also ventilating one's home adequately.

There are several easy ways to damp proof one's home too, by injecting damp proof solutions into the masonry, and filling up pores or gaps that may cause damp to travel.

Today, there are simple kits available that allow one to drill a hole in the wall, load a standard skeleton or cage gun with damp proof solutions (a kind of creamy substance), and fill the holes. Holes are spaced along the bottom of the external wall and filled in afterwards. They are easily visible in buildings that have been treated.


An older method, employed mostly by professionals is pressure injection. Here, water based fluids are pressure injected into walls to get rid of dampness.

Another complex method employed by professionals alone, is Electro Osmosis. As the name suggests, the process involves the use of an electric current.

This active system works by the introduction of a very tiny electric current into the wall just above ground level. This current sends rising moisture back to the lower level from where it is originating.

There is however a major drawback to this method. The walls will remain dry and free from moisture only as long as the electric charge is maintained.

So there you have it. Now dealing with dampness at home should be a little easier!

See introduction to underfloor heating >