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How to repair and paint a damp wall?


How many articles have you read about how to paint a damp wall?

How many of them solved your wall moisture problem?

Interior wall dampness cannot be repaired WITH PAINT.

The question is poorly formulated and should have been: How to repair a damp wall? First you have to eliminate the causes of the dampness.

Moisture in the walls, the risk of doing nothing.

If you don’t have a damp spot in your home, cast the first stone.

Having damp walls, mildew stains or peeling plaster is not only an aesthetic problem. This would be the slightest of detriments: we get used to it and that’s it!

A damp spot is not only uncomfortable because of its appearance, but it also has repercussions on the health of those who live in the house. Allergies, rhinitis, asthma, are some of the ills associated with the presence of chronic humidity. To that we must add the smell of mold in the air; clothes that never finish drying and fogged windows.

What’s more, the house itself also suffers. A wall with humidity or a ceiling that detaches ends up affecting the structure of the place we live in. If we don’t do something about it, it will probably be too late to fix it.


Aunque parezca un contrasentido, empecemos por lo que NO HAY QUE HACER, dicho en otros términos: NO SE DEBE PINTAR sobre una pared con humedad.

Toma en cuenta los riesgos de pintar sobre un lugar que está húmedo. En el 100% de los casos (o sea SIEMPRE) la humedad terminará reapareciendo. Habrás gastado tiempo y dinero para que todo esté como al principio.

Types of Moisture in Walls


1. Moisture permeation

Seepage moisture is the moisture that is produced by water entering through holes or cracks in the walls. Sometimes it is not even necessary to have cracks. The walls are composed of porous elements. If they are not properly protected from moisture, they will end up giving rise to stains.

How to solve the humidity by filtration?

Waterproofing paints (when exterior coatings fail).

Silicone or polyurethane sealants (when there are cracks or fissures in ceilings and walls).

Liquid membranes or asphalt membranes (when the roof or ceiling “drips”)

Repairing damaged plumbing (when it has been damaged).

This is a case of humidity in walls originated by external causes.

2. Moisture due to condensation

It is one of the most frequent causes of problems in the house. Moisture due to condensation is that which occurs inside the house due to excessive humidity in the environment. Understand this difference: it does not come from outside.

CONDENSATION is a phenomenon that consists in the passage of water from its vapor state to the liquid state.

When does condensation occur? When the ambient humidity collides with a cold surface of the house. Walls, ceilings, glass, floors. There it will meet a surface that has what is called a dew point, and it will end up condensing.

How to Remove Mold from Walls?

The market offers products specially prepared to eliminate fungi and molds, of practical application and excellent results. Their effectiveness is much greater than what you could achieve with any other home preparation system.

Removing humidity from the environment by means of dehumidifiers

3. Moisture by capillarity

Of all the types of humidity in walls, this is one of the most annoying because its presence does not depend on the weather: it will be present ALL YEAR ROUND.

Moisture from rising damp is generated by a natural process. Water and mineral salts from the soil where your house sits rise through the pores or capillaries of the materials used to build the walls of the house.

When the soil has excess moisture, it seeks to “give it up” to any porous material that surrounds it. The foundations absorb this moisture, which continues its ascent through the walls that form your house. At the end of this path it “explodes” as a problem, both indoors and outdoors.

How to Eliminate Capillary Moisture?

1.Redoing Insulating Coats. This treatment for damp walls is based on cutting from side to side the walls affected with rising damp (yes, demolish!), above the level of floors or baseboards, say about 15cm high. The idea is to replace that sector of the wall, by brick courses with water-repellent (impermeable) mixture, and some plastic or asphalt membrane, to achieve a hydraulic protection barrier that works as an insulating layer, preventing the ascent of humidity through the walls.

2. Resin injection. The system is very simple. It consists of making two rows of perforations of about 13mm in diameter in the lower part of the wall with rising damp, into which the silicone resin is poured until it fills them, allowing it to penetrate the pores and fill all the capillaries of the walls. When the product comes into contact with the humidity of the wall, its particles “solidify” (polymerize). This creates a chemical barrier that acts as an insulating layer (horizontal water-repellent insulation), preventing moisture from rising.


How to Paint a Wet Wall: The Complete Step by Step Guide

  1. Identify the Causes of Moisture
  2. Dry the Moisture in the Affected Area:
  3. Prepare the Surface Before Painting
  4. Applying the First Coat
  5. Applying Successive Coats

Final advice on what to do with a damp wall

You can’t paint over dampness and expect it to be solved that way.

There are different types of moisture. If we don’t attack the causes first, SURE (SURE!) that the damp spots on the wall and ceiling will come back.


  • Moisture from seepage
  • Moisture from condensation
  • Moisture from rising damp

Identify it and then repair damp walls, but, with proper treatment.

Don’t waste your time and budget “masking” moisture in walls! If you need help with any moisture problem you can make an appointment with us, we will gladly help you to repair and solve any problem.

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