If your walls darken in a corner, it’s no coincidence: find out what it really means (and how to fix it) (Page 2 ) | April 23, 2025

As soon as you notice a dark spot, there is no question of waiting for it to spread. The faster you act, the more damage you limit.

Start by ventilating the room well, morning and evening, even if it is cold. Ten minutes are enough to renew the air and remove the humidity. And if you are in a room often damp (bathroom, laundry…), that is all the more important.

Then we have to tackle the stains. A mixture of warm water and white vinegar can do wonders. For tougher molds, a little hydrogen peroxide may also be effective. But be careful: avoid vinegar on natural stone or marble surfaces, it could damage them.

Remember to keep the furniture away from the wall, even by a few inches, to let the air circulate. You’ll see, it changes everything.

And if the air remains heavy or moist anyway, consider installing a moisture absorber or a small electrical dehumidifier. It can make all the difference, especially in small spaces.

Small bonus trick: in winter, open the windows just a few minutes in the morning and evening. This is enough to remove the condensation that accumulates at night.

And to attach the useful to the pleasant, you can add a few drops of tea tree essential oil into the cleaning water. In addition to its fresh odor, it is known for its antifungal properties.

How can we prevent it from coming back? (Because we don’t feel like doing that again every month)

Once the walls are cleaned, the most important thing is prevention. The ideal is to settle the concern at the root.

If your ventilation system is not sufficient, consider installing a CCV or at least improving air extraction. A good ventilation works miracles.

Also keep an eye on the humidity in your home. A small hygrometer costs three times nothing, and you will quickly know if the air is too humid. The right fork? Between 40 and 60 per cent.

If your walls are prone to moisture, you can also apply a specific anti-humidity paint. It does not do everything, but it provides a welcome layer of protection.

And if you have any doubts about infiltration or insulation, it is better to call on a professional. A artisan or a moisture expert will be able to make a real diagnosis. Sometimes what we see on the wall is just the tip of the iceberg.

To avoid absolutely: repaint directly on a mold spot, hoping that it “caches the problem”. It’s a fence, and it’ll come back sooner or later. The same applies to gas replacement heaters without adequate ventilation: they release water vapor, which only worsens the situation.

What if, in spite of everything, the spots come back?

If the marks reappear despite all your efforts, it is because there is a deeper concern.

In this case, it is necessary to check the condition of the roof, the exterior walls, the gutters. Poor insulation or infiltration invisible to the naked eye may well be in question.

For capillary lifts, treatments exist: the most common is the injection of resin into the walls to block the moisture that comes from the ground. Anti-salpredom treatment may also be considered if the walls begin to crumble or launder.

Again, using an EGR artisan or a moisture expert can really save you more in the long run. A complete diagnosis makes it possible to target the real cause and to put the right solutions.

And if you are renting, above all, do not wait to warn your landlord. Mould can be a real health problem, and it is important that things are taken in hand quickly.

You are armed to face the black corners of your walls. With a little vigilance and good gestures, you can say goodbye to the stubborn humidity… and breathe more serenely at home.