Hydrotec since 1988
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For protection against moisture in the cellar and a healthy cellar

For protection against moisture in the cellar and a healthy cellar

Walls against the ground or against rock, like those in most cellars, are at high risk of being affected by moisture. To avoid any inconvenience, it is necessary to put in place protections:

Or from the inside: with the realization of a casing combined with a water-repellent injection.

Either from the outside: with the installation of multi-layered protection and the installation of drains along the buried walls.

These devices are very effective in combating moisture from walls in contact with earth or rock.

Where ?

  • Inside the cellars
  • On all the walls leaning against the earth or the rock


  • Damp cellar walls and floors.
  • Crumbling of paints or coatings
  • Water infiltration
  • Unpleasant odors, mold and fungus developing on stored items
  • Ambient humidity too high in basements.

Why do it ?

Hydrotec works in damp cellars to make them dry and healthy. After treatment, the cellars can be used for storage, to fit out a laundry room, a games room, sports room or an office.

The processing steps of waterproof protection treatment from the inside


Preparation of walls by stripping


Or preparation of walls by sandblasting


Implantation of an dampcorse barrier


4. Application of the tack coat



Application of Hydro + plaster


Creating a chamfer at the foot of the wall


Or installation of a drainage channel at the foot of the wall

(if necessary)


Waterproofing and floor finishing

with Egaline HY

The processing steps of waterproof protection treatment from the outside


Digging a trench

and careful cleaning of the entire surface of the wall


Implantation of an dampcorse barrier

to prevent capillary rise


Water-repellent cementing of the wall


Placement of a waterproof membrane

honeycomb with flashing in the upper part


Installation of the drain

surrounded by gravel and geotextile


Installation of a drainage mattress


Backfilling of the trench

FAQ – find out more


Given the evolution of prices in real estate, your cellar or your mezzanine are spaces that should be made habitableor at the very least usable and suitable for storage without worrying about the objects and foodstuffs being damaged by the moisture and fungi.
Sanitizing a cellar by applying a waterproofing coating on the inside of the walls against the ground helps prevent theproliferation of fungi and prevent the musty smell.
When accessibility permits, we also offer to treat cellars from the outside by opening a trench along the walls.


Cellar walls and walls against the ground are in contact with the basement which is impregnated by percolating rainwater or simply damp because the water table is not very far from the cellar floor level.
Not resistant to the pressure of moisture and the salts that accompany it, the plaster peeled off, the blistered paints give a leprous appearance to the walls against the ground.
After testing the walls with a high-frequency hydrometer, the technical advisor identifies the land levels, the levels of the adjoining soils and,following his readings, draws up an intervention plan.

Solutions to avoid

We strongly advise against the outright doubling of walls against the ground. Leaving the damp wall as it is and building a misery hidden partition is really not a lasting solution, it can even be dangerous: the void hidden by the dubbing or the counter-partition turns out to be a very good nest for critters. and other dry rot.

Solutions offered by Hydrotec: how to treat masonry against the ground

From the inside: the casing (or “water-repellent cementing”)

To have a healthy, dry cellar wall that can optionally be painted or covered with plaster, a casing plaster – water-repellent cement – should be applied to the carefully prepared walls.

Importance of wall preparation

To fight against the moisture of cellar walls, the quality of surface preparation is essential: sanding off crumbling paints, very carefully stripping off old peeled lime plasters, wet wall plasters. It is advisable to return to a clean, cohesive and perfectly clean wall in order to guarantee optimal adhesion of the new water-repellent coating. The quality of the preparation will prevent cracking and detachment of the new water-repellent cement plaster (Hydro +).

Application of the waterproof coating

The waterproof coating is applied to cellar walls in three layers:
1. the tack coat on a clean and porous surface,
2. first layer of “Hydro+” water-repellent plaster,
3. second coat of “Hydro+” plaster.

The work is carried out manually or with a pump and a mortar spray lance when the size of the site is substantial.

The cellar floor is wet

At ground level, it is sometimes necessary to redo the waterproofing under tiling. Damp cellar floors are also treated: after careful preparation (sanding, stripping, removal of any friable element, etc.), we apply a tack coat and a waterproofing grout to the floor.

When the hydrostatic pressure is very high, flooded cellar

When the cellar is flooded regularly, we install an interior drainage at the foot of the wall (drainage channel), or a HY-N20 drainage membrane over the entire surface of the humid floor of the cellar. The soil is then perfectly drained. The water goes to an inspection chamber or a sump equipped with a cellar pump.

Should a dampcourse barrier be installed in the shear walls, the perimeter walls?

When there is no plastic membrane (Diba) or a concrete slab separating the cellar from the rest of the building, we recommend the installation of a waterproof barrier: this is a treatment for capillary rise by injection of water repellent. The moisture contained by the casing will not take long to climb to the ground floor if we do not prevent it from doing so (in this case the expression rising damp takes on its full meaning).
The same goes for the partition walls of cellars which can be treated by injection at the level of the cellar floor, while the cased peripheral walls will be treated in height, at the level of the exterior floor (see technical drawings).
All of these anti-moisture treatments are complementary and essential to achieve optimal results, especially when you want to make a mezzanine or part of a cellar habitable.

Can we paint the walls of the cellar?

After the casing has dried, the cellar walls can be painted, butsince our casing plaster offers a beautiful, uniform, light gray finish (see photos on the services page), we recommend leaving it as it is. This avoids painting costs.
We do not recommend waterproof non-microporous paints and general-purpose anti-moisture paints sold in DIY stores.

Do crawl spaces and bases need to be protected from moisture?

Crawl spaces, basements also deserve to be well protected from moisture. These areas cannot be used as such, but it is preferable that water does not seep into them. As their name suggests, crawl spaces must also be fully ventilated to avoid seeing water vapor, mist condensing on concrete ceilings.


Whether on poured concrete, on solid brick walls, terracotta blocks or concrete blocks, the “Hydro+” coating is the casing solution that gives complete satisfaction for 98% of the coated m², from the first intervention. from Hydrotec.
For the remaining 2%, after-sales service intervention is sometimes necessary.
It is for this reason that a ten-year warranty is offered on water-repellent coatings applied by Hydrotec.
Hydrotec has been around since 1988, you can count on its determination to solve your moisture problem.

Injection treatment

The treatment consists of the injection of a water-repellent product (an approved product, in this case the CRD Gel or the H10eco liquid product).
During the injection, the injection product will migrate into the porous material of the wall and completely permeate a slice of masonry at the base of the walls.
Injecting a waterproofing product into a wall is a bit like inserting a waterproof membrane – but in liquid form – at the base of the masonry to create a tight and perfectly waterproof barrier that will prevent the capillary rise of water.

Injection products
Injection products are water repellents composed of silane and siloxane oligomers. The resin concentration is suitable for treatment by injection. Some products on the market are still formulated in a hydrocarbon solvent phase (toxic products). It is very surprising when we know the toxicity of solvents and we know that products in the aqueous phase (diluted in water) have been proven for several decades!
The products used by Hydrotec are formulated in aqueous phase. They do not emit any odor; they are no toxic: H10éco has obtained the Green label and the HCRD Gel, a product harmless to health, has meanwhile obtained a Class A + approval (the best efficiency among the products tested!) from the Belgian parastatal organization, the Scientific Center and Construction Technology (CSTC).

Following the injection treatment, the anti-saltpeter protection of the walls
Following the injection treatment, the moisture of the walls will begin its work of migration and evaporation. Drying a wall takes an average of 4 to 12 months. The drying time of a wall will depend on:

  • the thickness of the walls;
  • the amount of water contained in them;
  • the amount of salts present therein;
  • of the season (cold or hot, wet or dry season)
  • the presence or absence of heating;
  • the presence and quality of the plasters (cement or plaster? pickled or not?);

During drying, the saltpeter salts present throughout the thickness of the walls will also migrate to the surface. Some will come out and fall at the foot of the wall, but a quantity of salt will remain trapped and accumulate in the surface layer of the wall. Even though the treatment of rising damp has been carried out correctly, during the application of liquid plaster, the salts that remain trapped will migrate into the water used to mix the plaster. They are likely to pose a problem for the new coating applied to the wall. As the salts have the annoying tendency to dissolve in the water, they will spread in the new plaster coating and cause undesirable effects to the good progress of the operations: because of its hygroscopicity favored by the salts, the salted plaster can give believe that the treatment is not working well; blisters will appear in the new paint, swelling in the

Many individuals and building professionals often underestimate this important aspect of treatment. We cannot stress enough the need to provide saltpetre protection before applying the plaster coat. Most of our after-sales service calls relate to sites where, for various reasons, the saltpeter protection step was omitted, an important aspect of treating rising damp if there is one!

What does the anti-saltpetre protection consist of?
The anti-saltpetre protection is a primer (coating or membrane) that is applied to the perfectly stripped and cleaned wall.
To clean up a wall permanently, the anti-salt screen can be created in two ways:

  • either we apply, following the instructions in the technical sheet, the “Hydro+” coating, a cement coating added with resins which is very resistant to salts;
  • or a “Hy-N3 membrane” is attached to the wall, which is provided with a nylon mesh and cells to which the plaster will attach.

We prefer to use the Hydro+ coating because:

  • It straightens the wall and allows you to add a layer of plaster which will not be too thick, a common case on old walls (we recommend a maximum of 2cm of plaster on Hydro+).
  • Unlike membranes, it is microporous.
  • The coating is resistant and it strengthens the wall;
  • Thanks to its tack coat and its cement / quartz base, Hydro+ plaster is hard and very cohesive, that is to say it adheres perfectly to the wall;

The HY-N3 membrane can be useful because it allows you to move faster, but it has several drawbacks:

  • The wall sounds hollow to the touch, a void remaining behind the membrane;
  • The membrane is difficult to attach to the old heterogeneous walls (which are rarely flat);
  • A crack often appears at the junction between the HY-N3 membrane zone and the Hy-N3 membrane-free zone;
  • Plaster is difficult to do on a plastic membrane, ceiling workers don’t like to use it.
  • It is not microporous.

Plating and painting work after treatment
One week after applying the Hydro+ anti-saltpeter coating, the plaster topcoat can be applied without the risk of the reappearance of saltpetre crystals, spots or blisters in the The plaster is usually allowed to dry for a good month before considering coloring the walls. We recommend applying a good quality primer and microporous paint.