How to renovate rendered substrates, such as walls or facades in stucco or textured plaster, using a waterproofing system?

This solution outlines the procedure to follow for repairing cracks in rendered substrates, such as facades finished with stucco or textured plaster, followed by the application of the waterproofing system RD-Elastoflex and RD-Elastoflex Quartz.

This elastic and vapor-permeable coating provides highly effective protection against water infiltration, erosion, and carbonation, while maintaining the aesthetic of the building with a decorative finish.

Products presented

RD-Elastoflex

Technical paint designed for the waterproofing and protection of concrete, walls, and facades....

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RD-Elastoflex Quartz

Breathable waterproofing and protection coating for walls and facades with structured effect.

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RD-Cement Filler

Mineral powdery and dry mix based on cement, granulates and additives, for the repair of almost...

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Acryl W

High-quality water-based sealant based on acrylic dispersion.

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RD-Mur Fleece

Woven reinforcement fabric for liquid-applied waterproofing and wall coating systems on façades...

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The problem

Cracks in a wall with a decorative plaster coating, such as stucco, can provide entry points for water into the building. This moisture buildup may lead to staining and the formation of thermal bridges, which in turn promote mould growth inside.

Exposure to frost can cause the cracks and joints to widen, further worsening the damage. However, these deterioration processes can be halted and repaired in a durable and lasting way.

The solution

/!\ This solution addresses the repair of non-structural cracks. Consult an architect or engineering firm if necessary.

RD-Cement Filler – RD-Acryl W – RD-Mur Fleece

It is essential to address the root cause of the problem before applying a waterproof coating.

Depending on the nature and size of the cracks, RD Coatings offers a range of easy-to-use and highly effective products to repair them.

The use of RD-Mur Fleece reinforcement fabric is recommended for surfaces in poor condition. It significantly strengthens the waterproofing membrane against new cracks.

RD-Elastoflex & RD-Elastoflex Quartz

The application of RD-Elastoflex offers a certified and highly effective solution.

By combining it with RD-Elastoflex Quartz, a rougher surface is achieved, which maintains the irregular and decorative aspect typical of stucco.

It can also be used to hide certain imperfections in the wall.

/!\ It is advisable to carry out a preliminary test to visualize the desired result and determine the necessary thickness of RD-Elastoflex Quartz.

There are indeed many types of stucco finishes, and RD-Elastoflex Quartz is very versatile, with its finish varying depending on the amount applied.

Whether it is for a simple wall, a villa, a bridge, or a skyscraper, the RD-Elastoflex system has proven itself worldwide. From Brussels to New York, many buildings have been protected by this system for decades.

RD-Elastoflex is certified according to the EN 1504-2 standard, guaranteeing that it meets the strictest performance and durability requirements.

It is highly valued by architects and engineering firms for its exceptional properties, offering optimal performance and impeccable results.

• Permanent elasticity exceeding 600%, effectively bridging microcracks and maintaining the building’s waterproofing, even in freezing conditions.
• Breathability and vapor permeability, regulating interior humidity and ensuring optimal comfort.
• Very good resistance to CO2 diffusion.
• High resistance to weather conditions, including acid rain, UV rays, and dirt, keeping façades clean and aesthetically impeccable for years.
• Wide range of colors, including custom shades to meet all aesthetic requirements.

RD-Elastoflex thus offers durable, aesthetic, and high-performance protection for buildings and structures, regardless of climatic or environmental conditions.

System(s)

1/ Waterproofing system with localized crack repairs

	Product	Consumption	Dry film
Primer	RD-Elastoflex diluted at 10%	0,20 kg/m² 300 s/f-g	80 µ 3.2 mils
	or RD-Unifix	0,10 L/m² or more depending on porosity
Crack repair	Acryl W or RD-Cement Filler	Application in joints and cracks
Textured layer	RD-Elastoflex Quartz	0,50 kg/m² 130 s/f-g quantity to be defined based on the desired finish	200 µ 8 mils
Finish layer	RD-Elastoflex	0,40 kg/m² 150 s/f-g	155 µ 6 mils

2/ Waterproofing system with reinforcement fabric and crack repair

	Product	Consomption	Dry film
Primer	RD-Elastoflex diluted at 10%	0,20 kg/m² 300 s/f-g	80 µ 3.2 mils
	or RD-Unifix	0,10 L/m² or more depending on porosity
Crack repair	Acryl W or RD-Cement Filler	Application in joints and cracks
Reinforced intermediate layer	RD-Elastoflex + RD-Mur Fleece	0,40 kg/m² 150 s/f-g	160 µ 6.5 mils
Textured layer	RD-Elastoflex Quartz	0,50 kg/m² 130 s/f-g quantity to be defined based on the desired finish	200 µ 8 mils
Finish layer	RD-Elastoflex	0,40 kg/m² 150 s/f-g	155 µ 6 mils

Application conditions and work preparation

Environmental conditions (general requirements):

Minimum air and substrate temperature: 10°C / 50°F for 24 hours.
Maximum surface temperature: 55°C / 130°F.
Maximum relative humidity: 80%.
Surface temperature must be at least 3°C / 5°F above the dew point.
No threat of rain for 4 hours.

/!\ Notes

There must be no condensation on the surface during application and drying. Be cautious when working at the beginning or end of the season!
It is generally recommended to allow overnight drying between coats. However, the drying rates of water-based coatings depend on temperature, humidity, and wind.
From 15°C / 59°F, working conditions are more comfortable and productivity increases.
If the project is in a very hot area with intense sunlight during the day, avoid applying the system when the sun is most intense on the surface. Prefer to work early in the morning, late in the afternoon, or in the shade.

Immediate environment

Check for the presence of chimneys or ventilation openings that might release contaminants onto the surface to be treated. Neutralize their effects during the work.

Surface preparation

The surface must always be clean, dry, degreased, and free of any contaminants. Old paint layers that no longer adhere should be removed.

1. Biocide / anti-moss treatment

If there is moss, lichens, or other biological growth, treat it deeply down to the roots using a certified biocide available on the market.

Diluted bleach can also be used, though it provides a curative but not a preventive action. Be cautious of stains!

2. Efflorescence removal

Efflorescence is a white deposit that appears on the surface of construction materials, such as concrete or brick. While it is mainly an aesthetic issue, it can also indicate excessive moisture that could damage the material in the long term.

2.1. Dry brushing: Use a stiff-bristle brush to dry-brush the salt deposits. This removes most of the efflorescence without using water, which is important because water can dissolve the salts and draw them back into the material.

2.2. Water cleaning: If dry brushing is not sufficient, you can use water and a brush to clean the surface. However, avoid using too much water.

2.3. Using an acid cleaner: If efflorescence is persistent, a mild acid cleaner, such as diluted muriatic acid or a specific product for efflorescence, can be used. Apply it carefully following the manufacturer’s instructions, then rinse thoroughly with water. Be cautious, as acid can damage some materials and must be handled with care.

3. Existing paint and blisters

Check the adhesion of the existing paint. Scrape off anything that no longer adheres properly.

Puncture and cut open the blisters, and remove the poorly adhering paint.

Never paint over a poorly adhering coating!

4. High-pressure cleaning

Prévoir un nettoyage haute pression à maximum 120 bars / 1700 psi en fonction de l’encrassement du support.

Dans le cas d’une surface peinte, prévoir un nettoyage haute pression à maximum 275 bars - 4000 psi équipé d'une buse rotative à 0° d’angle. Cette étape permettra d'être certain que le revêtement existant adhère toujours correctement.

Repairs

/!\ Before carrying out repairs, it is important to determine the causes and neutralize them if necessary. Consult an architect or engineering firm for structural cracks.

1. Microcracks – width < 0.2 mm

In the case of a renovation where the RD-Elastoflex system is applied, these cracks do not need to be repaired or filled. The system is designed to easily bridge them.

2. Cracks > 0.3 mm and < 3 mm

These types of cracks can be filled with RD-Acryl W acrylic sealant or MS Polymer-type sealant. These sealants are waterproof and flexible. They can then be covered with the RD-Elastoflex system.

Never use silicones!

3. Cracks > 3 mm

Larger cracks will be repaired with RD-Cement Filler, a cement specifically designed for this type of treatment.

RD-Cement Filler is a cement that does not shrink during drying and adheres perfectly to mineral substrates.

Application of RD-Cement Filler

Remove any non-adhering parts until you obtain a sound and clean surface.

In the presence of reinforcing bars / rebars, remove rust manually with a wire brush. Remove the residues, clean, degrease, and dust. Apply a coat of RD-Elastometal to the reinforcing bars with a brush and let it dry for approximately 4 hours.

Depending on the depth of the cracks, apply a first bonding coat of RD-Cement Filler with a flat brush and let it dry. Then apply a second coat with a trowel or spatula.

Application of the waterproofing system RD-Elastoflex

Porous and/or chalking surface

If the substrate is porous, it should be thoroughly impregnated to saturation with RD-Unifix using a brush or low-pressure sprayer. Stop when the surface has a slightly satin appearance.

This allows for better performance of the following layers and prevents the RD-Elastoflex system from being absorbed into the concrete.

For moderately porous surfaces, another option is to dilute the first coat of RD-Elastoflex with about 10% water, saving a step!

If the surface is chalking, apply a thin layer of RD-Unifix beforehand.

On a smooth surface

Apply a first bonding coat of RD-Elastodeck, diluted with 25% water, or a layer of RD-Multiprim.

Reinforcement fabric RD-Mur Fleece

It is recommended to reinforce the waterproofing system with RD-Mur Fleece reinforcement fabric in the case of a surface with many active and/or large cracks.

RD-Mur Fleece can be applied locally or over the entire surface, depending on the case. It is available in rolls of 20 cm, 50 cm, or 100 cm widths and 100 meters in length. It can be easily cut with scissors.

For large surfaces with 50 or 100 cm rolls, it is preferable to have two people apply the fabric simultaneously with the first coat of RD-Elastoflex.

Start from the highest point.

Apply a strip of RD-Elastoflex with the same width as the fabric used to the surface.

Position the roll of RD-Mur Fleece against the strip of fresh paint to adhere it to the surface and gradually unroll it downward.

Simultaneously apply a coat of RD-Elastoflex to the fabric to fix it to the wall.

Ensure that the weight of the roll does not lift what has just been applied.

Allow for a minimum overlap of 5 cm – 2 inches between the fabrics.

This step is the most time-consuming but is absolutely necessary to guarantee the long-term performance of the system on façades with active cracks.

Let it dry for 12 hours.

Apply a second coat of RD-Elastoflex over the entire surface.

The prescribed quantity must be applied evenly and according to the recommendations. If it has not been achieved, apply an additional coat.

Job completed: The final system should be uniform in color and texture. The RD-Mur Fleece reinforcement fabric should be completely concealed, and the system should not have any craters.