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What are the causes of damp inside the home?

Do you have to contend with damp and moisture problems in your home? The good news is that finding the culprit should not be too difficult! In fact, there are only 3 possible suspects:

  1. the sky, which may cause rainwater to seep in
  2. the ground, which may push upgroundwater, also known as rising damp
  3. yourself and the other occupants of the home, as a result of condensation caused by you, sometimes exacerbated by bad habits

Below, we explain these 3 possible causes behind damp inside the home. All that remains for you to do is to identify the culprit(s) before you put in place the appropriate steps. Please note that several causes may overlap and combine.

Cause 1: rainwater infiltration


In most cases, the signs of damp are seen in the top sections of the walls.


These infiltrations are caused by a leak somewhere in or around building.
To solve the problem, you will need to locate this leak, which is not always easy as the damage can sometimes manifest itself somewhere quite far removed from the point where the cause of the problem lies. The root cause could well be somewhere over at your neighbours' for instance.  Moreover, the damage often remains invisible until after several months.

Here are some avenues worth exploring:

  • a pierced roof deck/roof underlay
  • a cracked roof tile
  • a zinc joint or fitting torn loose by the wind
  • a lead joint or fitting lifted up by nesting birds
  • a joint or fitting that has been severed or blocked, by dead leaves for example, between the rain gutter and the rainwater being evacuated down the gutter

Cause 2: rising damp


Rising damp usually affects ground floor walls across the walls' entire length and bottom part from where it can rise up to as much as 1.5 metres in height.


This cause often affects old buildings with walls that have no damp-proof course. But buildings whose damp course is made up of lead or bitumen sheets can get damaged too. We distinguish between:

  • lateral rising damp: groundwater rises up and gets into unprotected half-buried brickwork
  • vertical rising damp: the water rises up from the foundations

Cause 3: condensation and damp caused by the occupants


In the case of condensation, damp can suddenly crop up just about anywhere and always does so on a wall that is colder than the other walls. Sometimes condensation will appear after you have had double glazing put in. As the windows are no longer the coldest surface, the condensation manifests itself elsewhere.


On average, we give off at least 1.5 litres of water a day just by perspiring and breathing.
On top of this come other sources of damp such as plant watering, fish tanks, the laundry, the washing up, the bath tub, the shower, oil stoves and individual gas fire heating units without exhaust extraction… If the air is unable to properly circulate inside the home, this damp cannot be extracted and turns into condensation.
Condensation may be exacerbated by bad habits, such as:

  • leaving the washing to dry indoors without opening a window
  • boiling the water without the lid on

After you have identified the problem, it's time to take action!

Have you identified the cause(s) of your damp problem? Click here to find out what to do.

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