What mold kills on concrete walls

Removing mold: the most important tips

Nobody wants mold in their own four walls, because it not only looks unattractive, but can even pose a health risk. What you have to do in the event of an infestation and in which cases you can remove the mold yourself, you will find out below.

Removing mold: the most important tips
Removing mold: the most important tips

Mold should always be removed consistently. The first signs of an infestation are silver fish in the home or black, green or red mold stains on the window frames and water stains on the wall or ceiling. They all signal: too much moisture. And it is precisely under these conditions that mold spores settle and will soon be floating around all over the room. Their metabolic products are toxic and cause allergies in humans. In addition, mold damages the liver and kidneys in the long term.

What many do not know: molds are everywhere. In the soil, they help, among other things, to break down dead organic substances. And we even encounter it in food, for example in the form of blue mold in cheese. However, these species are harmless and cannot harm humans.

Black molds called "Aspergillus Niger" or "Alternaria Alternata", on the other hand, do. The microorganisms settle preferentially on wall and ceiling coatings, interior walls and tile joints. But also timber and furniture as well as plasterboard and leather are often affected. If you discover mold on your walls as a tenant, you should inform your landlord immediately. But mold is not always in a visible place. If there are any signs of an infestation, you can do a mold test.

How does mold develop?

Cold surfaces and too much moisture: These are the two prerequisites for mold growth. The mold does not begin to reproduce until the relative humidity is around 60 percent. However, if this humidity prevails for three to four days, a temperature of 0 degrees Celsius is sufficient for mold to grow.

Where does this moisture come from? A household of four produces around ten liters of water a day. The room air absorbs this amount - as invisible vapor. And it liquefies on cold surfaces, for example on window glass or in poorly insulated house corners. It is therefore all the more important to ventilate properly.

Other causes of mold are defects or age-related damage to buildings through which water and water vapor can seep in. Once water seeps in, the risk of mold increases enormously. Due to the permanently wet condition, even wood and insulation material start to mold. In such a case, be sure to check whether there is a leaking water pipe somewhere or otherwise water is leaking.

How bad is the mold?

The layman can distinguish between two levels of mold growth:

  1. In the corners of the room, on the walls, on the windows and in the joints, you will find small mold stains, so-called mold spots. It's really a bit moldy. However, the total infestation remains well below half a square meter.
  2. You discover large black spots on walls and behind pieces of furniture that run through the entire apartment. The musty smell is undeniable.

Good to know: If you discover mold infestation in your apartment that corresponds to the first stage, you have the option of removing the mold yourself, provided that the building has not yet been damaged and it is the first infestation.

Overview of mold types

Which means are suitable for removing mold?

If you want to remove mold yourself, it is best to use alcohol-based cleaning agents, vinegar water or washing water containing ammonia. Note, however, that these agents take some time to show effects and are only suitable for surface treatment.

Another option is to treat the infected areas with a steam cleaner. Make sure the surfaces are smooth. The steam is up to 100 degrees and penetrates into small cracks in the masonry.

Remove mold in case of light infestation

Moldy elastic joints in the bathroom or kitchen must be completely removed, the surface disinfected and then the joints renewed. Special sealing compounds (e.g. from Knauf or Ramsauer) will prevent mold from growing in the future.


If you only have small spots of mold in the masonry, it is sufficient to ventilate more often, to dry the infected wall and to work on it with a brush or cloth and muscle power. In addition, the areas are treated with alcohol-based cleaning agents (80 percent ethanol) or hydrogen peroxide solution (five to ten percent), if necessary with a salmiak thinner. Important: Wear a face mask when working and always wipe the surfaces carefully with a damp cloth. Finally everything has to dry well.

Removing mold: step by step

Step 1: Remove infected areas

Put on your face mask and remove moldy wallpaper, joints, paint and plaster until the surface is firm (scratch test), dry (water test: nothing should smear or rub off) and dust-free (wipe test: hand stays clean). In damp places, wallpapers come off the wall almost by themselves. Otherwise, apply wallpaper remover with the sponge. You have to scratch thick layers of paint with a wire brush beforehand. Dispose of the wallpaper in the trash immediately - it is full of fungal spores.

Step 2:Prepare the subsurface

Paint the prepared surface with a mineral primer and let it dry for 24 hours. Then embed the corner and plaster profiles vertically and flush in blobs of quick-release cement or universal filler. Then let it dry for a day.

Step 3:Plastering

Now mix lime plaster with water according to the instructions on the package, until it is lump-free. You can then plaster the walls with the trowel / smoothing trowel. Don't forget to pull it off on the profiles. In any case, apply more than ten millimeters of plaster in two passes.

Step 4:Felting

The next day, apply another two to three millimeters of plaster and work it with a felt pad. Then let it dry well again. Then the area is painted with anti-mold primer. If you want, you can also roll on white or colored anti-mold paint.

Step 5: embellish
If lime plaster is too rough for you or if you want decorative plaster or wallpaper in your home, you can now take a few beautification measures. To do this, coat the plaster with a mineral primer and let it dry. After that, you can smooth the plaster with a lime spatula. Only then is wallpaper or the like attached.

Tip: It has proven useful to encase cold house corners with special insulation angles. That keeps them warm and dry - and mold at a distance.

Remove mold in case of severe infestation

If the infestation is more severe, you must rigorously remove the mold; if in doubt, contact a specialist. Fighting mold with chemicals is not very sensible. These contain biocides that kill organisms but are released into the indoor air over months or even years.

When do you have to hire a specialist?

If you have tackled the initial infestation yourself, but mold spots form again after a few days or weeks, you should immediately commission a specialist to remove it. He can also make precise analyzes and measurements and thus find out the causes of the mold.

Remove mold from wallpaper, wood and furniture

If you want to remove mold from wallpaper or plasterboard, you must first remove it completely, because the mold usually penetrates deeper layers and spreads there.

Wood is also occasionally attacked by mold. It is then important to find out what type of mold it is. If only the surface is affected, it is sufficient to wash it off with a detergent. Wood stain also often occurs in weathered wood. In contrast to black mold, however, wood stain is not dangerous because it does not affect the load-bearing capacity of the wood. However, if you discover black mold on the wood, you must act immediately. Most of the time, the wood can no longer be saved in this case. Discard the affected parts and put in new wood.

Mold can also form on furniture, carpets, and other textiles. In the case of chairs, tables or cupboards, it is usually sufficient to clean the areas with a damp cloth. In the case of upholstered furniture or carpets, it is advisable to replace them.

Preventing mold: tips and tricks

  • Dry air is the best way to prevent mold. That means: you have to ventilate your rooms regularly and sufficiently. The cold air flowing in can absorb moisture again, so the room becomes drier. Good to know: For each ventilation action, around a quarter to a half liter of moisture disappears from a 20 square meter room.

    For hygienic reasons, the air should be completely exchanged every two hours: The best way to do this is to open the windows completely and ensure a draft. You should leave it open for six minutes in winter and twice as long in autumn and spring. There is enough time for air to be exchanged, but it is too short to cool down walls. Continuous ventilation in the tilted position is not recommended because only little air is exchanged. Only the reveals cool down and a lot of energy is lost. When ventilating the room, turn off the thermostatic heating valves so that you do not heat out of the window. Some models of thermostats close automatically when the windows are opened. If you want to save yourself the procedure, an automatic ventilation system can be installed.
  • In the bathroom, you should immediately wipe off the tiles and grout after showering or bathing, especially if the room does not have a window.
  • Mold does not like mineral substrates such as lime plaster or mineral paint. With the choice of material you can prevent mold colonies. Caution is advised with paste and wallpapers with plastic parts.
  • It is best to place your furniture on interior walls; a gap of at least six centimeters is advisable on exterior walls. Furniture with legs is also ideal. You can break through a base with a hole pattern or perforated sheet. This is the only way for the room air to circulate and take away moisture that otherwise easily collects behind or under furniture.
  • Only ventilate the cellar at night in summer, otherwise a lot of moisture will enter the house.
  • If the insulation is poor and the outer walls are thin, a lot of heat will migrate outside and the surfaces will cool down - for example in 1950s buildings. You have to insulate the house completely - either with internal or external insulation. However, the insulation from the outside is better, then all weak points are wrapped warm. Critical points are outside corners, roller shutter boxes, window reveals and plinth areas.