How damp gets into walls

Cause of Damp in Walls Diagram


Damp in Walls

To help you get rid of damp in the walls of your property we will explain how to identify the type of damp in your walls and how what may have caused it. This will aid you in choosing the right solution to remove damp.

Essentially there are three ways water can enter a wall;

  • from rain (Penetrating damp)
  • from the ground upwards (Rising damp)
  • from inside the building (Condensation)

Of course one way that water can enter a wall that’s not mentioned above is via a burst pipe.  If you suspect a burst pipe stop reading and call a plumber.

Rising Damp in Walls

The definition of rising damp is the movement of water in an upwards direction by the force of capillary action in a wall.

Tidemarks on the wall

Damp TidemarkThe most common sign of rising damp is the development of a brown tidemark on the wall. The tidemark usually signifies damp has been present for an extended period of time and the issue isn’t recent.

Tidemarks usually occur because either the damp proof course has failed or doesn’t exist, or the ground outside the home has been raised above the damp proof course level.

Water enters the bricks (or other material) and travels vertically up the wall because the building material is porus. Tide marks usually stop about one meter up the wall but can be of varying heights depending on the amount of water present and the material your walls are made from.


Can you see white salt developing on the wall?

If you can see salts forming on your wall it means it is constantly going through the cycle of drying, become wet, drying become wet etc When the moisture evaporates from the wall the heavier salts are left behind.

Penetrating Damp in Walls

Wet patch in middle of wall.

If you have a dark/wet patch in the middle of a wall that isn’t in contact with the ground it’ll probably be due to penetrating dampness.

If you can see the damp patch on an old chimney breast then its more than likely chimney salts. Salts form in the chimney when you burn fuel. These then ‘burn’ through the brick work presenting themselves. If you notice these patches coming and going it’s because the salts absorb mositure and dry out with varying temperatures (e.g day and night).

Condensation in Walls

There’s always going to be a certain amount of water in the air in your home. If surfaces in your home such as windows and walls get cold enough then the water in the air condenses on the surface forming water droplets on the windows or damp patches on walls.

If you find,  a damp patch on the wall it could be condensation. If the patch disappears in Summer then it’s the most likely culprit.

There are 2 effective ways to combat this problem in a relatively inexpensive way. If you have cavity walls you can insulate them. This means that the wall inside the house won’t become as cold and therefore moisture cannot develop on its surface. If you have solid walls you will need to use a dehumidifier. A dehumidifier will quickly remove excess water form the air.

Can you see any black mold?

Yes? Then the damp spot may be due to condensation. The surface of the wall becomes cold and water condenses out of the air onto the wall giving rise to a wet patch.

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