We insulate the facades of houses and blocks of flats from the outside across the province of Málaga — the system that quotes in Spain call SATE (Sistema de Aislamiento Térmico por el Exterior, known in the standards as ETICS) — and the final layer is the one most debated at home. Here are the options — renders of four types, stone, ceramic and brick —, what each one requires and a limit that is rarely mentioned before you choose: the colour.
What goes underneath the finish — insulation, mesh and detailing — is covered in what external wall insulation is and what it is made of.
Before colour and texture there is a bigger decision: whether the facade ends in a seamless coat or in pieces. It changes what goes underneath, what it can withstand and what can be done later.
A thin layer of finishing mortar spread over the base coat, with no visible joints and the colour mixed right through. It is the most widely used option, and it comes in a huge range of colours and textures. What you choose is its type — that is what the next section is about — and the texture, which comes from the tool.
Pieces bonded one by one onto a base coat that is more heavily reinforced than the one under a render. It is used more and more, and since 2018 it has had its own European assessment document. It stands up very well to knocks and is easy to keep clean in the face of pollution; on the other hand, the pieces have limits on size, weight and height.
The Spanish association of mortar and insulation-system manufacturers, ANFAPA, groups them like this: acrylic, siloxane, cement or lime, and silicate. They are not paints: they are a layer of finishing mortar a few millimetres thick — the data sheet of one of them gives 1.5 to 2 —, with the grain size setting the texture and the thickness.
Acrylic resins with aggregate in a range of sizes. It is one of the most widely used because it is very elastic, so it moves with hairline cracks instead of showing them, and because of its wide colour range. It repels rain and lets vapour through, though less than the other three.
When you want durability and a surface that dirt does not cling to.
An acrylic with polysiloxanes added. It keeps the acrylic’s advantages and gains breathability: vapour gets out more easily, and it performs very well against rain. The data sheets we have read also mention self-cleaning and protection of the render against algae and fungi.
On facades exposed to heavy rain and in coastal areas.
Mineral-based. It is the one that lets the most vapour through and the one chosen so that the appearance holds up over the years. It has a consequence that shows later on: the acrylic and siloxane renders whose data sheets we have read cannot be applied over silicate.
When letting the wall breathe and keeping the colour come first.
The traditional hydraulic mortars. They let vapour through well and perform excellently against the sun’s radiation. They are chosen for the natural look of a mortar wall, and they suit an old house that you want to keep looking like one.
In the restoration of traditional buildings.
Within each type, the texture comes from the tool: spatter, just as it comes out of the machine; knock-down, flattened with a trowel; or floated, worked over with a float. And the grain size governs the thickness, because the coat is spread as thick as its aggregate. Facade paints, which share resins with these renders but are a different product, are covered in painting your facade.
A dark colour absorbs more heat: the surface gets hotter and the colour deteriorates sooner, and on an insulated facade, what is underneath feels it too. Here it matters more than in the north: a south- or west-facing facade spends the whole summer in the sun. That is why some data sheets put a number on it.
Light reflectance value
20 is not black: it is a mid grey
20
Where the limit starts
50
Halfway up the scale
85
The data sheet’s example
Each grey is the one that reflects that percentage of the light. On screen it is an approximation: the number that counts is the one given next to each shade on the colour chart.
“It is recommended not to use dark colours on large areas of facade when they have a Light Reflectance Value ≤ 20, or a Total Solar Reflectance (TSR) ≤ 25” (our translation, like the other quotations from Spanish data sheets on this page). The first figure measures the light the colour reflects; the second, all of the sun’s radiation, including the part you cannot see.
The same data sheet advises especially against them on a system with EPS (expanded polystyrene), “as this could deform due to excessive overheating”, and excludes from the warranty any colours that do not comply. And ANFAPA’s guide on ceramic finishes asks the same for tiles: assess their colour and how much light they reflect according to where the building is, which way it faces and what insulation it has.
On the colour chart, next to each shade. On the chart for that data sheet, an 85 beside the colour is its light reflectance, and Xb30 means a total solar reflectance above 30. If the colour you like does not come with that figure, ask for it before you decide.
Bonding pieces onto insulation is not like tiling a wall: ANFAPA’s technical guide sets conditions for the pieces, for what goes underneath and for how they are laid. These are the ones worth knowing before you fall in love with a sample.
ANFAPA’s technical guide calls for a tile suitable for facades, in a small format — no larger than 300 × 300 mm —, 10 mm thick at most, no heavier than 20 kg per square metre, frost-resistant, with water absorption below 6% and laid up to a height of 30 m. And even when all of that is met, the final say lies with the technical team of the system manufacturer.
Where a render takes one layer of mesh, pieces take two, or one mesh with fixing anchors. The pieces are bonded with a cementitious adhesive to UNE EN 12004 and the joints are filled with a grout to UNE EN 13888. On top of that, the weight per square metre is validated with load tests under the Código Técnico (the Spanish Building Code), which take into account the height of the building and wind suction.
With slips that imitate facing brick, some ceramic and some flexible, bonded in courses onto the base coat with joints of at least one centimetre that are finished with a damp brush so that no gap is left. Or with a stencil: a self-adhesive template in the shape of the joints that is stuck onto a coat that has already dried, covered with the render and peeled off once the render has dried. Where the template was, the joint remains.
The same guide lists, among the features of a finish in pieces, that it is applied in combination with conventional renders. It makes sense on the ground floor, which takes the knocks, the bicycles and the terrace chairs: pieces below, render above, and an insulation system that does not have to look the same from one floor to the next.
The finishes guide ANFAPA published in 2025 adds glazed finishes to ceramic and stone. In the end, what can go on your facade is decided by the specific system.
One manufacturer specifically recommends siloxane render for facades exposed to heavy rain and in coastal areas, and it is worth making sure whichever one you choose has protection against algae and fungi: some data sheets include it and say so. Salt and the wall that sits underneath the system are another conversation.
What the coastal climate does to a facadeAn insulated facade ends up being repainted, and not with just anything. The data sheets of the acrylic and siloxane renders we have read say they must not be applied over lime, distemper or silicate, so a lime or silicate finish then calls for maintenance that is compatible with it. And the new colour has to pass the same limit as the first one.
The shade varies slightly from one production batch to another, so the data sheets ask for batches not to be mixed on the same section of wall and, on large facades, for the work to be broken up at joints or panels; one of them wants these to be 10 to 15 m². Nor is it applied in direct sun, strong wind or with rain due in the following hours: if it gets wet before it dries, it stains.
How much the finish weighs in the total, along with the insulation, the access equipment and the state of the wall, is explained in the cost of external wall insulation per square metre.
Yes, and over the years it is the normal thing to do: maintaining an insulation system means maintaining its finish. The paint has to be compatible with the render already there and let vapour out just as the render does, and if the finish is silicate or lime, that rules out the paints that cannot go over it. Before choosing, it is worth knowing which render your facade has.
It can come very close. A render can be left as it comes out of the machine, in a spatter finish; flattened with a trowel, in a knock-down finish; or worked over with a float, which is the floated finish. That last one is what one of the data sheets describes as “similar to scraped single-coat mortar”.
For details, yes; on large areas, it is not a good idea. One data sheet for an insulation-system render recommends not using colours with a light reflectance of 20 or less on large areas, advises especially against them over expanded polystyrene (EPS) and excludes from the warranty any that do not comply. And 20 is not black: it is a mid grey.
Yes. As well as finishes in natural or reconstituted stone, there are ornamental finishes for insulation systems that reproduce classical architectural features, such as mouldings or cornices, designed for buildings of historic value. In those cases the finish is decided together with what the town hall will allow.
It depends on the product. One of the data sheets gives it as dry in about 24 hours at 20 °C and 65% humidity, asks you to wait that day before doing anything else on top and puts full curing at about 15 days. In cold, damp weather it takes longer, and that can show in how even the colour is, especially with strong shades.
We do not give figures without measuring, but we can tell you why. A finish in pieces involves more work underneath — double mesh or anchors —, as well as the pieces, the adhesive and the grout; a render is a primer and one coat over the base. Between renders, what changes is mainly the material.
Send us a photo of the facade, tell us which way it faces and what finish or colour you have in mind. We will tell you what fits the system, whether that colour is within the limit and what we would check when we come to see it.