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ITPreparing a façade for exterior wall painting: the 5 essential steps
Preparing the façade is the most decisive stage of any exterior wall painting project. A poorly prepared substrate (dirty, flaking, damp or cracked) compromises the adhesion of the new coating and shortens its life. A properly prepared façade, on the other hand, gives a result that lasts and reduces future maintenance costs.
Cleaning, stripping, specific treatments: each step matters and needs the right products. This complete guide sets out the method recommended by SCALP SAS for preparing a façade properly before repainting.
Step 1 - Assess the condition of the façade before any treatment
Before choosing a product or a method, a visual survey of the façade is essential. It determines the level of intervention needed and avoids treatment mistakes.
Step 2 - Façade cleaning: removing dirt and deposits
If the existing coating is sound and in generally good condition, a ‘simple’ clean is enough to prepare the surface. The aim is to remove all dirt, pollution deposits, grease and marks that could affect the adhesion of the new coating.
SCALP FACANET PAE
SCALP FACANET PAE is a heavy-duty cleaner specially designed to remove all types of dirt from façades. This no-rinse, chlorine-free product can be overcoated after 48 hours. It offers a fast, effective way to restore soiled surfaces to their original condition.
This cleaner is ideal for stone, brick, cement, fibre cement, concrete, and cement-based and organic renders.
Professional No-Rinse Facade Cleaner – SCALP FACANET PAE
SCALP FACANET PAE is a professional, no-rinse cleaner designed for fast and effective facade cleaning on roofs, walls, floors, and facades. Its powerful, pH-neutral formula removes urban deposits such as soot, dust, and fine particles while preserving the natural look and integrity of the surface.
This versatile cleaner is suitable for a wide range of materials, including natural and reconstituted stone, brick, concrete, fibre cement, and hydraulic or organic plasters. For large or hard-to-reach areas, SCALP FACANET PAE can be applied using drones, offering fast, uniform, and safe coverage without the need for rinsing.
SCALP PRONET
SCALP PRONET is a multi-purpose façade cleaner designed for cleaning and degreasing external walls before a coating or protective treatment is applied. It works in depth to remove all common dirt from substrates such as cladding, façades, walls and floors. Its targeted action rids surfaces of atmospheric pollutants, grease and other residues that could affect the adhesion of a new coat.
Degreaser and cleaner for facades – SCALP PRONET
Step 3 - Stripping old paint and coatings
Stripping is essential if the façade has several layers of paint, flaking areas or a degraded coating. It provides a clean, stable substrate and better adhesion for the new coating.
SCALPEX SD NG: ultra-fast masonry paint remover for textured coatings, adhesives and graffiti
SCALPEX SD NG is an ultra-fast stripper, specially formulated to remove thick textured masonry coatings, thin films, adhesives, inks, varnishes and graffiti. This high-performance product works on a wide variety of substrates such as plaster, concrete, stone, brick, glass mosaic, timber and mineral renders.
Thanks to its viscosity, it is particularly suited to vertical surfaces such as façades and external walls.
Professional Paint Stripper for Façades – SCALPEX® SD NG
SCALPEX® SD NG is an ultra-fast chemical paint stripper designed for the rapid and safe removal of waterproofing systems, RPE coatings, thin paint films, adhesives, inks, varnishes, and graffiti. Free from methylene chloride, NMP, and NEP, this high-performance paint stripper remover delivers effective action across a wide range of substrates, including plaster, concrete, stone, brick, glass mosaic, wood, and mineral coatings.
Its optimised gel viscosity ensures excellent adhesion on vertical surfaces, making it the ideal paint remover for façades, exterior walls, and architectural elements.
SCALPEX SD+ : flash-action stripper for textured coatings and thin films
SCALPEX SD+ is a flash-action stripper. It strips thin films in just 15 minutes, waterproofing coatings from 30 minutes and thick textured coatings from one hour. Its exceptional speed makes it ideal for projects that need rapid repainting.
This stripper is compatible with a wide range of substrates, such as plaster, concrete, stone, brick, glass mosaic, timber and mineral renders. Its optimum viscosity prevents runs, making it ideally suited to vertical surfaces such as façades and external walls.
Ultra-Fast Gel Paint Remover for Façades – SCALPEX® SD+
SCALPEX® SD+ is an ultra-fast gel paint stripper designed to efficiently remove paints, waterproofing systems, thin RPE coatings, and graffiti from a wide range of exterior surfaces, including render, concrete, stone, brick, wood, and mineral substrates.
Thanks to its innovative “flash effect” formula, it softens coatings in just 15–60 minutes depending on thickness. Ready to use, this gel paint remover is simple to apply with a brush or airless sprayer. Odourless and DCM-free, SCALPEX® SD+ is ideal for rapid, high-performance stripping on vertical façades and exterior walls.
SCALPEX AQUA 50 : water-based, biodegradable stripper
SCALPEX AQUA 50 is a water-based stripper formulated to remove building paints, thick textured coatings and façade waterproofing systems quickly. It works fast even in extreme weather, with an application temperature range from -5 °C to 50 °C.
SCALPEX AQUA 50 stands out for its ability to remove a thin film in just 20 minutes, a façade waterproofing system in 30 minutes to 1 hour, and a thick textured coating in 2 to 4 hours.
Ultra-Fast Wall Paint Remover Gel – SCALPEX® AQUA 50
SCALPEX® AQUA 50 is a professional wall paint remover gel designed for rapid paint removal on walls and exterior façades. It efficiently eliminates paints, textured coatings (RPE/RSE), waterproofing films, and thin layers from concrete, render, brick, and stone.
Its highly gelled, water-based formula adheres perfectly to vertical surfaces, making it ideal for façades, cladding, siding, and other exterior walls. Thanks to its ultra-fast action, coatings can start softening in as little as 20 minutes, making it the go-to solution for outdoor renovation and maintenance projects.
Step 4 - Treating specific problem areas: efflorescence, salt deposits and graffiti
Some areas of a façade can have localised problems which, if not treated before painting, will reappear through the new coating.
Efflorescence and salt deposits: causes and treatment
Efflorescence, sometimes called ‘salt bloom’, appears as whitish deposits on mineral surfaces, particularly concrete, stone and brick. The deposits come from mineral salts carried in water that migrates to the surface and evaporates. The problem is often made worse by damp or rising damp.
Salt deposits of the nitrate type, meanwhile, are crystalline deposits produced by the chemical reaction between salts present in the building materials and moisture. Both problems are often linked to damp or rising damp.
Recommended solution: SCALP NDS 72
To remove efflorescence and neutralise salt deposits, SCALP NDS 72 is the ideal efflorescence remover.
- Targeted, effective action: this product quickly removes the whitish deposits on walls and neutralises alkaline substrates, leaving a sound surface.
- Optimum preparation: applying SCALP NDS 72 provides a clean, stable base, improving the adhesion and life of the paint.
- Versatile: SCALP NDS 72 can be used on concrete, stone and brick façades and other mineral surfaces, indoors or out.
Efflorescence remover & brick salt treatment – SCALP NDS 72
SCALP NDS 72 is an efflorescence remover designed to eliminate white salt deposits and neutralise alkaline residues following cleaning or stripping operations. Its powerful acidic impregnating formula delivers fast, deep action, ensuring mineral surfaces are fully stabilised and ready for finishing treatments.
This professional solution is particularly effective for treating efflorescence on brick, concrete, plaster, and stone, restoring the appearance of façades while improving coating adhesion and long-term durability.
What Causes Efflorescence in Bricks and Masonry ?
Efflorescence in bricks occurs when moisture carries mineral salts to the surface of porous materials. As water evaporates, visible white deposits form, affecting both appearance and substrate performance.
If left untreated, efflorescence on brick and masonry can:
- Damage surface appearance
- Prevent proper adhesion of paints and coatings
- Lead to recurring moisture-related defects
- Weaken porous building materials over time
SCALP NDS 72 penetrates deep into the substrate to dissolve salts, neutralise alkaline residues, and stabilise the surface to help prevent recurrence.
Step 5 - Final check of the substrate before applying the new coating
Once cleaning, stripping and specific treatments are complete, a careful check of the whole surface is essential before applying the undercoat and the final masonry paint.
What the final check should cover
- Cracks: any unfilled crack can worsen under thermal cycling and let water in behind the coating; render repair should be completed first
- Weak or friable areas: an unstable substrate must be consolidated (stabilising primer, filler) before anything is applied
- Uniformity of the surface: stripped, treated or repaired areas must have the same level of porosity to ensure even absorption of the coating
- Dryness of the substrate: the façade must be completely dry before painting (residual moisture under 5 % depending on the product)
A well-prepared façade means a repaint that lasts. By following these five steps, you give yourself an excellent result and long-lasting protection against the weather.
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