Moist walls – causes and solutions

Posted by Anna Urban

The faster you react to damp walls, the fewer problems you will have later. Both financial and health problems. But where does the water that settles inside come from? More importantly, how do you solve the problem of damp walls? You can find the answer and other useful tips against moisture and mould in our guidebook.

Moist walls are created by water, the worst enemy of masonry. Once infiltrated, even the smallest amount can cause great damage, which can cost you dearly – not only from a financial point of view, but also from a health point of view. Because if walls draw moisture for too long, mould inevitably develops. This can cause headaches, fatigue, exhaustion, skin and mucous membrane irritation, asthma attacks, restlessness, bronchial diseases or allergies. Even animals are not spared.

However, damp walls are not only caused by us residents, also structural damages like for example a leaky pipe network or roof as well as heat bridges let wetness penetrate into the house. A tiresome topic, for which you need above all patience and time – because should be botched with the repair of damp walls by no means!

What are the causes of damp walls?

The causes for damp walls are various, a regular control is therefore indispensable. Most often one of these reasons is behind it:

  • Incorrect heating, ventilation and drying
  • If the difference between room temperature and the outside temperature is too great, condensation will form on the wall and within a very short time you will have damp walls. Tip: Do not tilt your windows too long, but ventilate them for 5 to 10 minutes – especially after cooking and showering.
  • Technical problems: appliances such as washing machines, dishwashers or air conditioners can lose water. If this one way makes its way into the wall, damp walls are inevitable. Also make sure that after such water damage the walls are dried long enough so that no moisture remains in the masonry.

Structural defects

  • Moisture due to thermal bridges: If more heat deviates outside at individual points in the house than in adjacent areas, moisture can also settle here. Thermal bridges occur particularly on roller shutter boxes, window frames and lintels, radiator niches or balconies. The trigger is often a wrong insulation of building parts: If individual parts of a building are insulated slightly, they cool down more quickly than well insulated areas. The result: the surface temperature is lower and moisture settles. As a result, mould can develop.
  • The balcony waterproofing is leaking.
  • The window seal or window pane is leaking.
  • The outer facade has cracks.
  • The roof has a hole or the roof tiles are displaced so that rainwater penetrates into the interior of the building.
  • The humidity of the ground makes its way up the wall. A horizontal barrier (horizontal waterproofing) normally prevents this. But especially in old buildings, this waterproofing is often no longer functional or completely missing. Without this protective device, the water can reach the top of the masonry capillarity.
  • The seepage water penetrates into the cellar. With a vertical barrier (vertical waterproofing), the building components that come into contact with the ground become impermeable to water. The same applies to slope water.

Good to know: For the subsequent installation of a horizontal waterproofing you can count on costs between 150 and 250 Euro per square meter (without costs for the expert).

Material wear

  • The seals of the shower or bathtub are leaking. After a few years of daily use, the silicone joints may have holes through which water will flow into the wall when showering or bathing. Even the smallest quantities are sufficient to cause major damage. Especially if the moisture gets behind the tile mirror. 
  • A water pipe is leaking. It can be both a fresh water and a sewage pipe.
  • A burst pipe that either has not been detected over a long period of time, or a burst pipe that has been repaired immediately but not correctly repaired.

How can damp walls be identified?

From the very first suspicion, you should verify the problem with a so-called moisture meter. The easy-to-use device measures how damp the walls are and thus confirms your suspicion – or gives the all-clear.

If walls are wet or damp over a long period of time, they begin to smell earthy and musty. Another indication of damp walls can be a permanently fogged window where condensation runs down. Or the wallpaper can come off by itself: Either piece by piece, it usually starts at the corners, or it simply falls off in the wallpapered strips. The tile mirror can also fall off if the wall behind it is damp. In the worst case, if the water has flowed into the wall in large quantities or over a long period of time, even the brickwork itself begins to crumble, the wall paint with the plaster bursts off and the bare stones appear underneath. Clear indications of damp walls are also spots that can vary in colour from white to yellow. They arise because the water dissolves the salts from the mineral building materials.

If brown-black fungi or even green-black mould spots have already formed on the damp walls, it is high time to consult an expert. You will hardly be able to control this type of damp wall on your own.

Problem solutions for damp walls

1. Find causes

Since water does not just flow straight ahead, you often have to think “around the corner” when investigating the causes of damp walls. Sometimes it helps to look at the building plan of your house. Which rooms share a wall or have superimposed walls? In the case of single-storey apartments, this is easy to see – in the case of multi-storey houses, it is often the building plan that opens one’s eyes. It is all too easy to forget that the shower drain, for example, is only a few metres above the wall in the living room. Or that there is a window above the stain on the ceiling. If you took pictures of the pipes before plastering, take them out and take a close look at them: In which wall does which pipe run?

2. Contact Person

If you live for rent, you must inform the landlord immediately if the walls are damp and discuss all further steps with him. If you are a homeowner and have no idea where the water comes from, you can contact a TÜV expert, for example. Do-it-yourselfers can try within their own four walls to solve the problem, i.e. the origin of the water that has penetrated the house: seal the balcony, tighten the silicone joints or something similar. If you are not one of the most talented craftsmen in the world, then you better call the craftsman responsible to remove the damp walls. This is also advisable for large projects such as a roof renovation or a burst pipe. Because the leak must be closed here professionally.

3. Drying the wall

An expert should be consulted here. This is because a layman could make serious wrong decisions and thus contribute to the spread of mould – for example by stopping the drying process too early or generally not carrying it out properly. If the moisture is already too deep in the masonry, in the worst case individual bricks or even entire wall sections must be replaced. After the damage analysis, talk to the expert about which part of the work you could possibly do yourself to reduce costs. After completion, you should install a dehumidifier in the affected room to improve the air.

Drying damp walls: what methods are possible?

  • Horizontal methods to protect against rising soil moisture in masonry (capillary action)
  • Ramming method: If you have a so-called continuous horizontal joint in the damp wall of your house, the expert will ram a wedge-shaped chrome steel sheet into this joint with a lot of pressure, so that the mortar is displaced upwards and downwards. If the joint is not present, the professional can cut the masonry at the appropriate point. This is mainly done in older houses.
  • Drilling method: This procedure seems to be the simplest for the home craftsman in the fight against damp walls: Holes are drilled with a very good drill and then filled with a chemical sealant. The agent is injected into the wall through a storage vessel attached to the boreholes.
  • Pressure injection: The first step for pressure injection is also to drill many holes in the damp wall. Then the chemical sealant is injected into the wall – but with pressure generated by machine.
  • Infrared plates: Another way to dry damp walls is to hang infrared plates in front of the wet masonry and transport moisture to the surface of the wall, where it is then dried using the infrared plates. The panels can also be used as an additional measure after a series of previous drying processes.
  • Electrophysical process: In this method, a small box is attached to the damp wall to displace the water from the masonry by means of an electrical voltage. The permanent voltage of up to 60 volts is to ensure that the wall dries.

Vertical methods for protection against oppressive wetness

  • Exterior waterproofing: After the building fabric has been checked, the earth around the building is removed: areas void of air such as faulty joints or old plaster must be repaired. Then sealing sludge, primer and a bitumen thick coating are installed. Tip: When closing the excavation pit, burl membranes and filter fleeces protect the waterproofing from damage.
  • Internal waterproofing: If a wall in contact with the ground is damp, it should also be treated from the inside: After drainage, this is usually done using waterproof sealing plasters and sealing slurries. If the masonry still shows moisture, appropriate renovation plasters are to be used.

Good to know: With the vertical method, it is important to allow the building fabric to dry completely before waterproofing.

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