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The symptoms of rising damp


Rising damp

Rising damp appears above all on the level of walls located on the ground floor and in basements.

It is particularly common in old houses; sometimes in new houses when the water tightness of the walls has not been carried out correctly.


The most frequent symptoms are:


  • - Deterioration of the paint
  • - Unpeeling of wallpaper, plaster and plinths
  • - The appearance of saltpetre

Treatment of rising damp


The system of treatment of rising damp which we utilise consists of the pressurised injection, in holes drilled in a line at the bottom of the walls, of a water-repellent product creating a water-tight barrier against rising damp.




Treatment of rising damp
  1. 1- Strip the ceiling
  2. 2- Deep drilling
  3. 3- Shallow drilling
  4. 4- Injection
  5. 5- Apply anti-saltpetre treatment (water-repellent cementing/membrane) before replastering.


The injection of the moist walls is performed by means of an injector and a membrane pump working at a varying pressure between 2 to 15 bars.
The pressure should adjusted according to the density of the materials to be injected.
Permanent control of the pressure is ensured by means of a manometer mounted directly on the injector.




Hydrothan 10éco (micro-emulsion of silane-siloxane resins in aqueous phase, without hydrocarbons, completely odourless and non-toxic) provides permanent protection against the capillary rising of moisture inside walls.
Its very high powers of dispersion permit use in all types of walls, regardless of the humidity content and thickness.
Hydrothan 10éco has been awarded the Excell Green Label


Treatment of rising damp : injecting the walls



In most cases, it is not possible to rehabilitate plasterwork damaged by water and saltpetre.
The walls must be stripped to a height slightly higher than that of the affected area. Stripping is also required for the elimination of saltpetres (nitrates, chlorines, sulphates) from walls at different concentrations. These compounds can prevent humidity from evaporating, aggravating the hygropscopic properties of the wall.






Despite the effectiveness of the treatment, the migration of residual salts (salpetre) towards the surface of the walls may damage new plasterwork.
To prevent this problem, a physical anti-saltpetre barrier should be applied before replastering. This physical barrier should consist of an additional cementing with Hydro+ or an HY-N3 plasterable membrane.




The drying time of the moist walls after treatment is highly variable, varying from 4 to 12 months.

The variability factors in drying are:

    • - The presence /absence of plasterwork, various fillers, cementing, paints, wallpaper, etc.
    • - The quantity of water contained in the wall.
    • - The content of hygroscopic salts. These salts may originate from the ground, the urea of stable animals or the presence of fertilizers.
    • - The ventilation of the areas, the presence/absence of an extractor hood in the kitchen, ventilation in the bathroom, etc.


    Rising damp : humid wall before treatment
    Rising damp : wall after treatment
    Humid wall before treatment

    Wall after treatment



    In Technical Information Note 162, the C.S.T.C. has noted that the treatment, correctly performed, will last as long as the wall itself. This is why Hydrotec rising damp treatment is guaranteed for 30 years.







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