Industry news

Many people struggle with it, but there is a solution to waterlogged walls

Published

2025. 08. 12. 14:50

Magyar Építők

Photos: Mapei Kft.

In almost every street in Hungary, there is at least one house whose walls smell musty, whose plaster is peeling off in patches and whose residents have long since stopped painting because they know it's no use. This phenomenon is not only an aesthetic or comfort issue, but also poses serious long-term health and structural risks. But what exactly causes walls to waterlog and what can be done about it?

„The hidden weak point of old houses is often waterproofing. Or rather, the lack thereof,” says Béla Markovich, managing director of Mapei Kft.. Most residential buildings constructed in the 1950s and 1960s do not have effective waterproofing, or it has lost its effectiveness over the decades. In such houses, moisture seeping up from the foundation and soil slowly but surely "creeps up" the walls through pores and capillaries.

The process is visible to the naked eye: the paint runs off, the wall is damp to the touch, there are salt blisters in places, and sooner or later mould appears, which is dangerous not only for the building but also for your health.

Solution not only at symptomatic level

"Many people try to combat waterlogging with aesthetic renovation, such as repainting, plastering or mould-killing, but these solutions are only temporary because they do not address the root of the problem," says Béla Markovich. "A lasting result can only be achieved by blocking the moisture pathway and getting the water trapped inside out of the masonry."

The approach proposed by Mapei consists of two key steps: firstly, blocking the path of moisture by creating a so-called chemical barrier, and secondly, drying out the wall and treating the salts with a special plaster system.

Chemical barrier - blocking the path of moisture

The spread of capillary absorbed water can be stopped by injection. In this case, a special silicate or silane-based solution is injected into the masonry, which spreads through the material to create a water-repellent layer in the masonry. This layer prevents the water from spreading, while not reducing the breathability of the wall - a key factor in drying out.

Once the moisture has stopped spreading, the next step is to dry out the walls. This is where the drying plaster system comes in, which not only 'hides' the damp spots, but also plays an active role in evaporating moisture and 'trapping' salts. Thanks to its special composition, the system allows the wall to "breathe" so that moisture can escape through the plaster without causing further damage.

The structure of the plaster layers is also important: first comes the primer, then a 2-3 cm thick layer of drying plaster, followed by a finishing coat. The final coating (e.g. paint) must also be vapour-permeable so that it does not block the path to drying.

And what about the cellars?

In addition to masonry waterlogging, the protection of basements and foundations in contact with the ground is also of paramount importance. Here, different, thicker, more durable waterproofing materials are needed, which not only protect against water, but also resist soil pressure, thermal fluctuations and minor structural movements.

Modern polymer-bitumen coatings, for example, are faster to apply than classic sheet insulation, require no joints and are much more flexible. They are particularly recommended for the outside of basement walls or for horizontal surfaces where moisture can penetrate through large surfaces.

Only a systemic approach works in the long term

The most important thing to remember is that waterlogging cannot be treated with "get-away" solutions. A new coat of plaster is not enough, a mould-killing spray is not enough. Masonry dampness is a serious and complex problem that requires proper diagnosis and a systems thinking solution.

According to the experts at Mapei, the biggest mistake you can make is procrastination. The longer you leave moisture in the walls, the more salt and harmful substances are released, which can damage the structure and degrade indoor air quality.

When should you seek professional help?

If the wall shows signs of water, mould or salt build-up, it is not just an aesthetic defect, but part of a process. In such cases, it is worth calling in an expert to assess the source of the damp, the condition of the structure and recommend the most appropriate technology.