Home · Render & decorative plaster
Render & decorative plasterRender is the only part of your facade you will still be looking at thirty years from now. Yet the conversation is usually about colour and nothing else. This page sets out what else matters: which type of render suits your facade, what each grain size does, why dark shades are not always possible, and where cracks and green growth come from.
What sets one render apart from another is the binder. It determines whether your facade can breathe, how well it repels water, how flexible it is and how long the colour lasts. No single type wins on every count — the question is which one suits your substrate.
| Type | Breathes | Repels water | Flexible | When to choose it |
|---|---|---|---|---|
| Silicone resinsiloxaneStandard on EPS | Good | Very good — water beads off | Yes, the least prone to cracking | The usual choice on external wall insulation with EPS. It combines water repellency with sufficient vapour transport and a wide colour palette. |
| Silicatepotassium silicateOn wool or old masonry | Very good | Good | Limited | Naturally alkaline, which discourages algae and mould. Often chosen with mineral wool insulation. It calls for craftsmanship and the colour palette is more restricted. |
| Mineral renderlime- or cement-boundRenovation | Very good | Moderate | Little | Breathable and ecological, common in thicker coats on solid masonry. Less advisable on EPS: barely flexible, so a higher risk of cracking. |
| Acrylic / synthetic resindispersionLimited | The least of the four | Good | Yes | Film-forming and inexpensive, with the widest choice of colours. It is precisely that film that makes it less suitable on a facade that needs to release moisture. |
Classification according to the Belgian ETICS Manual and the product documentation of the system suppliers. Exact performance varies from brand to brand and is set out in the technical data sheet of the chosen system. One rule always applies: insulation, reinforcing mortar and finish come from the same system holder — mixing them voids the approval and the guarantee.
Grain size shapes the look of your facade even more than colour does. It also determines how forgiving the facade is of unevenness — and how quickly it gets dirty.
| Grain | Look | Requires | Dirt sensitivity |
|---|---|---|---|
| < 0.5 mmsmooth render | Crisp and almost flat, architectural | A perfectly flat base coat; usually finished with an additional silicone resin paint | Low, but every unevenness and every repair stays visible |
| 1.0 – 1.5 mmfine grainMost chosen | Modern and crisp, the current standard | A flat, carefully levelled base coat | Low to medium |
| 2.0 mmmedium grain | The classic middle ground, a little more relief | Less critical about small irregularities | Medium |
| 3.0 mm and coarsercoarse grain | Rural, rustic, plenty of shadow play | Little — it hides the most | The highest: a coarser texture holds on to more dirt and algae |
In Belgium, 1.0, 1.5 and 2.0 mm are the common grain sizes, with 1.5 mm the most widely used. Beyond the grain, the way it is applied also shapes the look: a scraped texture gives fine horizontal or circular grooves, a floated finish a closed, flatter surface. We bring samples to the site visit, because judging a grain on a screen simply does not work.
This is the point where the conversation stalls at many facade companies, and where disappointment sets in when it only comes up afterwards. On an insulated facade there are limits to how dark you can go.
The Belgian ETICS Manual puts it plainly: the lightness value of the colour must be higher than 20%. That value runs from 0 (black) to 100 (white) and describes how much light — and therefore heat — a colour reflects.
Some system suppliers apply stricter limits, for instance a minimum of 30 for mineral render and 20 for silicone resin. Which shades are possible with your system is set out in the technical data sheet. We lay that sheet next to the colour sample instead of guessing.
A dark colour absorbs the sun's heat. On a solid brick wall that heat is carried away by the mass behind it. On an insulated facade it cannot be: behind the render sits insulation, so the heat stays trapped in a layer just a few millimetres thick.
The result is large temperature swings between day and night, expansion and contraction, and eventually cracks. EPS itself starts to deform above 80 °C — a temperature a black facade reaches in summer sun.
Then there are two routes. The first is a finish with heat-reflective technology (TSR), where the colour looks dark but takes up far less heat — it exists, it costs more, and not every colour can be made in it. The second is dark accents instead of a dark facade: a plinth painted dark, dark window surrounds or brick slips in a deep shade, on a facade plane that stays light.
What we will not do is carry out your colour and leave the consequences to you. If a shade is not possible, we say so before the quotation and we look together for the closest one that is.
These are the two things people ring us about. Neither is inevitable, and neither is solved by putting paint over it.
A well-applied render lasts twenty to thirty years. What it needs is not a major intervention but attention at the right time.
Walk around your house and look out for the first green growth, hairline cracks and damage to the plinth. Buildwise has a free maintenance checklist for exactly that. What you spot early is a small job; what you leave for three years is a facade renovation.
At limited pressure and with a product suited to your type of render. How often depends on the orientation and the surroundings: a north-facing facade under trees needs attention more often than a south-facing one on open fields. There is no fixed interval.
After a clean, a water-repellent treatment can protect the facade for several years against moisture uptake and therefore against new algae growth. It is not a layer you can see and it changes nothing about the colour.
A sound render with a faded or dated shade does not need replacing: clean it, stabilise it where necessary, and apply a vapour-permeable facade paint over it. That is a fraction of the cost of new render — more about this on the facade painting page.
Small cracks are filled and painted over with a vapour-permeable system. With large or recurring damage, repairing does not help: the problem then lies underneath and has to be solved first.
Climbing plants, shrubs against the wall and a gravel strip that splashes: all three keep the bottom metre of your facade wet. Half a metre of distance does more for your render than any product.
Render straight onto masonry is possible, provided the substrate is stable, clean and rough enough. Old paint has to come off completely — render never bonds durably to paint. Smooth substrates such as concrete always need a bonding primer.
Render without insulation costs roughly €40 to €80 per m² excl. VAT. With insulation you are looking at €110 to €150 per m². The gap seems large, until you see what both include: the same scaffolding, the same substrate preparation, the same reinforcing layer, the same finish, the same detailing around every window. Only the insulation board is added.
So you pay for the most expensive items either way. If you do it now without insulation, you will pay for them again in fifteen years when you do decide to insulate — and you will have missed fifteen years of savings. Render without insulation is a defensible choice if your facade is already insulated or if, structurally, not a centimetre can go outwards. In every other case we tell you honestly that it is a missed opportunity.
Not sure whether external insulation is possible on your home? The choosing insulation page sets out when external, cavity or internal insulation is the right route, and when we advise against external insulation.
Work out your indicative price online first. At the free site visit we bring samples along and hold them against your facade, in your light.
VediWorks is one of Vedi Group's four companies. Interior painting, a post-construction clean or maintaining shared areas: one contact, the same crews, the same standard.
