Resin Injection: The Reference Technique Against Rising Damp

Principle of the Technique

Rising damp occurs because porous materials in an old wall (brick, stone, lime mortar) allow ground water to migrate vertically through a network of micro-channels via the physical phenomenon of capillarity. Resin injection aims to fill these micro-channels throughout the entire thickness of the wall, at a given height, with a hydrophobic product that repels water instead of absorbing it.

Once polymerized, the resin forms a continuous barrier that cuts off capillary migration: water can no longer rise above this level. The wall above the barrier continues to dry gradually through natural evaporation, without new moisture input from below.

The effectiveness of the technique directly depends on the continuity of the barrier: the slightest untreated point can allow water to bypass the injection, which explains why the spacing and depth of the drill holes are critical parameters.

Resin Types and Choice Criteria

Three families of resins are commonly used, each adapted to different contexts:

The choice of product depends on several technical criteria: the nature of the wall material, wall thickness, degree of water saturation at the time of treatment, and the presence or absence of dissolved salts. A serious professional adapts the product after diagnosis, rather than systematically applying the same resin to all jobs.

Stages of the Project

A resin injection project follows a fairly standardized sequence, generally completed in 1 to 3 days for a detached house:

1. Prior Diagnosis and Layout. Humidity mapping (moisture meter, calcium carbide test), determination of the treatment height and areas to cover, including cross-walls often overlooked by less rigorous contractors.
2. Drilling Holes. Holes are drilled at regular intervals (generally every 10 to 15 cm) at the base of the wall, at a height chosen just above the exterior ground level, with a slightly downward angle toward the interior of the wall.
3. Injection Under Pressure or by Gravity. Depending on the wall's porosity and the chosen product, injection is done either by low-pressure pump or by gravity via cartridges or a slow diffusion system.
4. Diffusion Control. A serious professional checks that the product diffuses well laterally in the wall (via visible weeping or a posteriori control) and adjusts the quantity injected if necessary.
5. Sealing Holes with a compatible mortar, without sealing before being certain that the injection was sufficient.
6. Wall Drying, a period during which no finish should be applied.

Expected Results and Full Drying Time

A point often misunderstood by homeowners: installing the waterproof barrier is fast, but the complete drying of a wall that has been saturated for years is not. Once capillary migration is cut off, the water already present in the wall must evaporate naturally through the surface, which generally takes between 12 and 18 months for a standard wall, and can exceed 24 months for very thick walls.

During this period, it is normal to continue observing some residual humidity or even a slight reappearance of surface stains: this does not mean that the treatment has failed. Applying a plaster or waterproof paint too early is the most frequent mistake: it traps residual moisture and can cause new peeling of finishes.

A so-called 'sanitizing' render (lime-based, breathable) is recommended during the drying phase, as it lets the wall breathe while limiting visible salt migration on the surface.

Resin Injection vs. Other Techniques

In practice, resin injection and peripheral drainage are often complementary rather than competing: drainage reduces the amount of water available in contact with the wall, while injection cuts off residual migration inside the material.

Average Price per Linear Meter in 2026

The price of resin injection generally ranges between 80 € and 150 € per linear meter in 2026, depending on several factors: wall thickness, site accessibility, nature of the chosen product, and region. The full detail of prices by technique, with updated ranges, is available in our guide dedicated to 2026 damp treatment rates.

Certifications and Standards to Check with the Provider

Before signing a quote, several points must be verified:

• Technical assessment or certification of the product used, ensuring it has been tested for this specific use.
• Ten-year insurance (decennale) and/or thirty-year guarantee offered by the company on this type of service.
• Detailed quote specifying the product used, the injection method (pressure or gravity), the spacing of the holes, and the exact surface area treated—a vague quote is a warning sign.
• Verifiable references and reviews on similar projects, ideally with several years of perspective.

Frequent Errors and Scams to Avoid

The damp treatment sector unfortunately attracts aggressive commercial practices, particularly toward the elderly. Some signals to watch out for:

• Too rapid free diagnosis systematically leading to a need for urgent work, without objective measurements presented to the client.
• Quote signed the same day under commercial pressure, without a cooling-off period.
• Lack of mention of the exact product used or the injection method.
• Promise of immediate results ("dry wall in 2 weeks"): physically incompatible with the drying time of a saturated wall.
• Hole spacing that is too wide, leaving untreated areas.
• Absence of a written guarantee or a guarantee limited to less than 10 years for this type of structural work.

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