Waterproofing for facades, walls and exterior walls all along the Málaga coast. A damp stain on the wall that faces the street can have three different causes, and only one of them is fixed by treating the facade from the outside. Here is how to tell them apart, where rain really gets in and what can be done in each case.
What the levante (the easterly wind) and the salt air do to a facade, and what yours is made of, is covered on the facades page.
All three leave a stain, and from inside the house they are hard to tell apart. But each one is fixed in a different place, and mistaking one for another means paying for a job that does not stop it.
It gets in from outside, almost always at a detail or a junction and rarely through the middle of a sound stretch of wall. The stain shows on the inside of the wall that faces the street, grows after rain and dries out over the following days. This is the one that waterproofing the facade fixes.
A damp band at ground level, at the same height all along the wall, which does not depend on whether it has rained. It is water from the ground rising by capillary action. The Spanish Building Code (Código Técnico de la Edificación, CTE) stops it with a waterproof barrier at the base of the wall, and no product applied on the outside, higher up, will hold it back.
Black spots in the corners, behind furniture, around the windows. It does not come from outside: it is the vapour from the house settling on the coldest part of the wall. Waterproofing the facade does nothing for it.
If what you have is black spots in the corners, look at how mould forms on a cold wall, not at the facade.
The Building Code, in its document on protection against damp, devotes a whole section to what it calls puntos singulares (critical details): the places where the facade is interrupted or finished off. That is where the rain usually gets in.
The critical details
Water gets in at the edges and junctions, not through the open wall
Diagram, not to scale. At the bottom, in ochre, water rising from the ground by capillary action: it is stopped with a barrier at the base of the wall, and waterproofing the outside will not cure it.
The measurements are those of Documento Básico HS 1, the Building Code’s section on damp. They are a way to look at an existing facade and see what it is missing.
When the window is set back from the outer face of the wall, the standard requires the sill to be finished with an external sill sloping outwards at 10° or more, a drip on its underside at least 2 cm away from the wall, and each end built at least 2 cm into the jamb. A flat sill, or one with no drip, leaves the water running down the wall just below the window.
Above, a drip on the lintel so that water does not run underneath to the frame. All round, the joint between the frame and the wall sealed with a bead set into a groove in the wall, between two parallel edges. A bead of silicone stuck on the outside, over the paint, is not what the standard describes.
The roof-terrace parapet is finished with a coping sloping at 10°, drips set 2 cm off the wall face and the joints between pieces sealed. A cornice or eaves projecting more than 20 cm has to be waterproof on top and have a drip at the edge: otherwise the water it collects ends up on the wall below.
When a railing or a pole is fixed into a horizontal surface of the facade, the joint between the fixing and the building has to keep water out: sealed, with a rubber gasket or with a metal cover piece. It happens, for example, with railings fixed from above into the edge of a balcony.
To stop water from the ground rising, the Building Code requires a waterproof barrier across the full thickness of the wall more than 15 cm above the outside ground level. And if the facade is porous, a plinth more than 30 cm high, in a material that absorbs less than 3%, sealed at the top against the facade, to take the splashback.
None of these faults is fixed with a product on the open wall. The detail is put right, and then, if need be, the surface is treated.
The Building Code does not treat every facade the same. It asks each one for a degree of impermeability, from 1 to 5, according to two things about the place where the building stands: how much rain falls on average, by zone, and how much wind it gets.
The wind exposure is worked out from the height of the building, the wind zone and the surroundings. And this is where the coast counts: the standard puts in the most exposed terrain class, alongside open country, land at the “edge of the sea or of a lake with a clear area of water in the direction of the wind at least 5 km long”. An urban area, by contrast, falls into the other class.
For a building up to 15 m tall, the table gives a wind exposure grade of V3 in an urban area and V2 at the edge of the sea, whatever the wind zone. It is the standard putting into numbers what anyone who lives on the seafront already knows.
That degree is met by the wall as a whole: the outer coating, the cavity or the insulation, the thickness of the brick leaf, its joints and the render on the inside. That is why a facade is not “waterproofed” just with what is put on top of it.
For exposed brick, stone or concrete that you want to keep on show. It soaks into the pores and repels rain without forming a film or changing the look. It has clear limits, and the data sheet we have read spells them out: it does not bridge cracks, it does not work against water under pressure or on horizontal surfaces, and it does not replace the main waterproofing of the wall.
A render or a paint that covers the whole wall. The Building Code does not ask for it to be watertight at all costs: it asks for adhesion, for it to follow the movements of the substrate without cracking, and for enough vapour permeability that it is not damaged by vapour building up between it and the wall. Waterproof to rain, open to vapour.
Often the facade needs nothing on the open wall: it needs a sill with its drip, a properly sealed coping or a window-frame joint redone. It is the least glamorous job and, when that is where the water gets in, the only one that stops it.
The data sheet we have read asks for a sound, dry, clean surface with no paint on it; a three-day wait if it has been washed; cracks wider than 0.3 mm sealed beforehand; at least two coats, the second before the first has dried; and protection from rain for the first four hours, at 20 °C. Not in strong direct sun, and not in strong wind.
Which paint repels water without trapping vapour, and which one closes hairline cracks at the cost of breathing less: it is all explained on the facade painting page. And if there are cracks, before anything else, how they are read and repaired.
Water travels inside the wall before it shows, and the stain can appear a long way from where it entered. That is why you look outside first, above the stain: the sill, the lintel, the balcony above, the parapet. Treating the wall without having found the way in is spending money in the wrong place.
The Building Code measures what a facade has to withstand from the rainfall of the area and its exposure to wind. A building at the water’s edge, with open water in front of it in the direction of the wind, falls into the most exposed terrain class. The same block two streets back, in an urban area, falls into the other one.
“Facade waterproofing” can mean a water repellent, a paint or repairing three window sills. To compare, ask for each offer to set out the product, the area and which specific points are repaired first. If it names none, it is worth asking why.
Only if that damp is rain getting in from outside. If it is water rising from the ground by capillary action, or vapour from the house condensing on the cold wall, waterproofing the outside will not get rid of it. That is why the first step is knowing which of the three it is.
Not without removing it first. The data sheet we have read is clear: other coatings cannot be applied over a treated surface without first removing the protective layer. So if the plan is to paint later on, it is worth deciding that before the water repellent goes on.
It depends on what is there and what you want to see. Exposed brick or sound stone calls for a water repellent, which does not change its appearance. A painted render calls for facade paint, which also covers it. And if the water is getting in at a sill or a joint, neither of them will stop it: the detail has to be fixed.
The Building Code sets out a maintenance table: the coating and the critical details every three years, looking for cracks, detachment, damp and stains; cracks and deformation in the main leaf of the wall, every five. On the coast, it does no harm to check the sills and the edges of the balconies after every storm.
We do not give a price without seeing the facade, because it is not a single job: it can mean treating a whole wall or redoing two window sills. First we find where the water is getting in, and then we give a fixed price for what needs doing.
Send us a photo of the stain from inside and another of the facade from outside, at the same height, and tell us whether it grows when it rains. With that we can start looking for where the water gets in.