Béton ciré

Béton ciré: how it is laid, and what separates one system from another

Béton ciré is the opposite answer to the same question a tile answers. Where a terracotta floor is made of hundreds of fired pieces, each with its own colour, béton ciré is one continuous surface — two or three millimetres of mineral coating trowelled over what is already there, with no joint anywhere in it. It is not a paint and it is not a traditional plaster: it is a system — primer, base coats, finish coats, sealer — and that is exactly what makes two quotes hard to compare.

Laid in coats, over a fortnight

A béton ciré is not a coat but a sequence, and most of the calendar is drying. Mercadier publishes its own for the EBC: substrate preparation, first coat, second and third wet-on-wet, sanding, protection, then handover. Nine to fifteen days, preparation and finish included — which is why a job is not judged by how long the trowelling takes.

  • Day 1substrate preparation
  • Day 1 / 2first coat
  • Day 2 / 3second and third coats, wet on wet
  • Day 3 / 4sanding
  • Day 8 / 9protection
  • Day 15back in service

Thickness depends on where it goes, not on the product

This is what a "covers 10 m²" kit quietly skips: the same quantity covers half as much outdoors as it does on a wall. The minimum thicknesses Mercadier publishes for the EBC, on a smooth substrate:

  • 1 mmwall decoration
  • 1.5 mmfloor
  • 2 mmshower
  • 2 mmover tile
  • 3 mmexterior

What actually separates two systems

A headline price per m² says almost nothing until you know the thickness it was worked out at and what the kit contains. The criteria producers publish, and disagree on:

  • Yield in kg/m² per mm2.1 for the EBC against 1.25 for the PMB: at the same thickness the second uses half the material
  • Powder plus binder to mix, or ready-mixedHarmony sells both (TRADIT and ISY) side by side, at different prices
  • Grain"very fine" at Mercadier: the finer the grain, the tighter the surface closes under the trowel
  • Mechanical strengththe EBC states 34–50 MPa in compression and 10–13 MPa in flexion, tested by the CEBTP
  • The protectionmatt, satin or gloss: it is what makes the surface washable, and it is often sold separately
  • Indoor air emissions (VOC)class A+ where the producer publishes it

Comparing two prices honestly

Two producers both say "from €30/m²" and are selling different things. Arcane and Harmony sell the job: their packs are labelled in square metres, primer and sealer included. Mercadier sells the material: a 29.5 kg sack whose area follows from the yield and the thickness, with primer and varnish on top. That is why the catalogue shows both — the stated area where a producer gives one, the calculated area where it gives a yield — and why primers and sealers are listed beside the systems.

Figures quoted from the producers' own published data sheets.

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