The question is really about sequence
Cleaning and coating are often quoted as alternatives — as if a building chooses one. They are not alternatives. They are two steps of the same operation, and the order is not negotiable.
Clean, then coat. Always.
Why coating a dirty facade fails
A modern facade coating is not paint. The formulations that work on tile, stone and render are penetrating: a silane or siloxane that travels into the pore structure of the substrate — typically 5 to 15 mm — and lines those pores so water beads rather than wicks in.
That mechanism depends entirely on contact with the substrate.
Between the coating and the substrate on an uncleaned facade sits: atmospheric particulate, traffic film, biological growth, mineral deposits from years of rain runoff, and in coastal areas salt. Each of those is a barrier to penetration.
The outcome is threefold, and all three are bad:
- Patchy penetration. The coating goes deep where the substrate is exposed and barely at all where it is not.
- Reduced service life. A coating specified for 7–12 years does not deliver that if it never bonded properly.
- Sealed-in contamination. The dirt is now under a hydrophobic layer. The next clean cannot reach it.
That third point is the expensive one. Coating over dirt does not defer the cleaning; it forecloses it.
The interval between the two
This is where projects most often go wrong in the other direction — cleaning properly, then coating too soon.
A pressure wash puts a considerable volume of water into a porous substrate. Pores that are full of water cannot admit a penetrating sealer. Coat too early and the product sits on the surface instead of travelling into it, which produces the same shallow-bond problem as coating over dirt.
How long is enough depends on material, weather and how much water went in. In dry conditions, at least a day; after heavy washing or if rain intervenes, longer. It is a site call, not a calendar rule — which is why we survey moisture rather than working to a fixed gap.
The practical scheduling consequence: cleaning and coating a whole building is a one-to-three-day operation, not a same-day one.
What coating actually does
Being precise about this avoids disappointment.
It slows soiling. A hydrophobic surface sheds water, and water carries the dirt off with it. Rain does more of the cleaning, so the interval between washes lengthens.
It reduces water absorption. Less water in the substrate means less freeze-thaw stress, less efflorescence, less of the moisture that drives tile debonding from behind.
It resists UV degradation. Slows the breakdown of the surface and, on rendered or painted facades, colour fade.
It does not repair anything. It will not bridge a crack, re-bond a hollow tile, or stop water entering through a failed joint or a defective sealant line. Those are repairs, and they belong before the coating — because coating over a defect makes the defect harder to find and no less active.
The right order, in full
- Survey. Establish what is actually wrong — cracking, hollowing, joint failure, water ingress paths. See facade health check.
- Repair what the survey found that needs repairing.
- Clean. Remove everything the coating would otherwise be applied over.
- Dry. Let the substrate reach a moisture content that admits the coating.
- Coat. Formulation selected for the substrate — silane for most masonry, siloxane emulsion where drift resistance matters, modified acrylic where budget or tinting governs.
Skipping step 1 is common and expensive. It produces a beautifully clean, well-coated facade with an unaddressed crack behind it, and a rediscovery two years later.
What it is worth
On a sound facade, coating extends the interval between cleaning cycles and slows the deterioration mechanisms that lead to tile detachment. On a facade with unaddressed defects, it is a cosmetic expense that makes the next survey harder.
The survey is what tells you which one you have. Book an asset assessment or call +886-2-7733-7678 — and see facade waterproof coating for the formulations and how they are applied.
