If you're looking for the practical preparation steps, read Painting a damp wall: step-by-step preparation. Here we focus on diagnosis and how to check the surface is ready.
The mistake of starting with the roller
Painting straight over a damp stain can hide the problem for a while without fixing it. The EPA recommends not sealing or painting materials that are still wet or show biological contamination. Before opening the tin, it's worth knowing whether it's condensation, water ingress or rising damp; each situation calls for different steps first.
Step 1. Identify how and when it appears
A stain near a cold junction may be linked to condensation; a tide mark that gets worse when it rains points to water ingress; damage rising from skirting level calls for looking into how the materials and the ground behave. These are clues, not conclusive proof. Follow-up photos, indoor relative humidity and a check of plumbing help narrow down the cause.
NeutralySalt Primer
Anti-salt treatment: it helps prevent salts (salt deposits) from crystallising on the surface. It lets the wall breathe.1 L and 5 L · 25–30 m²/L
Step 2. Fix the source and check it has dried
Leaks, water ingress or building problems are repaired first, and excess indoor vapour is controlled where relevant. Drying shouldn't be judged only by the wall changing colour. In complex cases, a technician can use measurements suited to the material and compare how they evolve. No one should promise the same drying time for every property.
Step 3. Restore the surface
Poorly bonded films and dust are removed; where there's efflorescence, the salt crusts are removed by hand before choosing a treatment. Dark stains require proper cleaning and moisture control, following the relevant precautions. A surface that looks dry but is powdery isn't ready for the finish either.
Step 4. Choose treatment and primer
On mineral walls with salts, NeutralySalt Primer can be considered within its limits of use. On new, absorbent or weak surfaces, Sellador Total L44 is designed to regulate absorption and improve adhesion. They aren't interchangeable: they're chosen according to the material and the problem observed. Compatibility between coats must be checked before applying them.
Step 5. Apply the intended finish
Pared Seca can be used as a finish on interior walls with condensation and in some sheltered outdoor areas, always on a dry, sound and clean surface and with ventilation maintained. MATE5000 AntiHumedad is for indoors. It's essential to follow the data sheets and respect coats, temperature and times: the finish must not replace repairing water ingress first.
Expected result
Proper preparation improves the conditions for the coating to do its stated job. It doesn't turn a paint into a structural repair system or guarantee that a wall stays dry if water keeps getting in.
Technical and scientific sources
- EPA, A Brief Guide to Mold, Moisture and Your Home
- Historic England, Decontamination: efflorescence
- ASTM D3359-23, Standard Test Methods for Rating Adhesion by Tape Test
Guía escrita y revisada por el Equipo Humix Paint con los datos de las fichas técnicas de cada producto. La pintura actúa en la superficie: si el agua sube del suelo o entra de fuera, primero se trata la causa.
