Appearing on walls prone to moisture, the saltpetre must be treated as soon as possible to prevent the damage from spreading over the entire structure, thus tending to weaken it. The solutions to combat this phenomenon are numerous, some are preventive while others are curative.
The causes of saltpeter on the walls of the house: potassium nitrate
Saltpetre is a mineral salt that appears on the walls in the form of a particularly unsightly whitish layer. It mainly colonizes the lower part of the interior walls of a house that is the victim of a humidity problem. It is the potassium nitrate used to make building materials that turns into this unsightly whitish deposit when it comes into contact with oxygen and moisture.
In general, saltpeter appears in old buildings, cellars and other old structures. Not affecting the upper floors, it appears only on the damp walls of the ground floor and its height does not exceed 1.5m. As a general rule, this phenomenon is mainly caused by a problem of capillary rise and faulty ventilation in the house. It is accompanied not only by the formation of a whitish deposit but also by friable material, detachment of plaster and coating, formation of halos or even rotting of the masonry. Saltpetre affects all types of supports, whether plaster, concrete, cement or even bricks.
Preventive treatment of saltpetre
Prevention is the best remedy to avoid saltpetre. In this context, combating humidity, which is the main cause of the problem, will be the priority. The first thing to do is to determine the level of humidity in the room. If it exceeds 50%, you will have to think about installing an electric dehumidifier. This measure is highly recommended, especially in the winter period because the lower part of the walls is generally colder than usual, which favors the appearance of capillary rise.
Another tip: the installation of a good drainage system that prevents the infiltration of groundwater. This requires regular maintenance. Also remember to wrap it in a geotextile film to prevent the proliferation of roots which could be responsible for clogging the device. Moreover, to reverse the polarity of the walls, performing electro-osmosis is also a solution. This technique is effective in combating capillary rise. Last method and not least: the installation of a waterproofing membrane which comes in the form of high density polyethylene or bitumen and rubber.
Curative treatment of saltpetre
If unfortunately saltpeter has already invaded your walls, curative actions are necessary accordingly. It is essential to remove all coatings that have been affected because they risk contaminating the rest of the still healthy structure. The first step is to vigorously scrub the wall with a couch grass brush. Then wash with hot water containing Marseille soap or detergent. Rinse while making sure all whitish deposits are gone. Then, apply a filler to repair any cracks that have appeared on the wall.
Once the structure is dry, it is essential to apply an anti-saltpetre product that neutralizes and changes the chemical composition of the salts. When laying the final coating, remember to choose microporous wallpapers that allow the walls to breathe. An anti-mould, waterproof and bactericidal paint is recommended if you choose this coating.
What is the cost of a professional intervention to treat saltpeter?
To treat saltpetre and prevent it from invading your home, you need to act quickly and at the heart of the problem to eradicate the cause. Indeed, if you content yourself with masking the saltpeter based on surface products, the humidity remains present within the walls and continues its destructive progression.
The humidity diagnosis
Calling a professional for a diagnosis is optional, but highly recommended. He will thus be able to measure, using quality devices, the humidity level and the expansion of it within your home. In addition, it can help you identify the entry point of moisture in order to find the right solutions to treat both surface saltpeter and water present in the walls.
The cost of such a diagnosis varies between 300 and 800 euros on average depending on the area to be covered.
Dry out damp walls
After identifying the source of the dampness, drying the walls will be an essential step to eliminate all the water retained in the structure. For this, it all depends on the surface to be covered and the method used by the professional.
Count on average between 20 and 500 euros per linear meter depending on the solution chosen.
Clean and repair walls
The cleaning and repair of the walls carried out by a professional will be invoiced to you in terms of labor and material.
For coatings and anti-saltpetre treatments to be applied to your walls, count between 20 and 200 euros per linear meter, depending on the type of treatment product used. Add to that the cost of labor, which can be between 25 and 50 euros per hour depending on the professional and the region. Obviously, the larger the area to be covered, the longer and more expensive the service will be, hence the interest in acting without delay.