Short answer: yes. Concrete is one of the better substrates for a mineral finish, because it is rigid, dense and does not move much once it has cured. Venetian plaster, Marmorino, lime and microcement all go over it. The questions that decide whether the job succeeds are not about the finish at all. They are about how dry the concrete is, what is on its surface and where it is going to crack.
Three things to establish first
Is it dry? New concrete carries a great deal of water and gives it up slowly. A slab or a wall that looks dry can still be releasing moisture from the inside for months. A finish bonded to it before that has finished will blister, stain or lose its bond. We take a moisture reading with an instrument and work to the limit in the technical data sheet for the product being applied, not to a rule of thumb about how many weeks it has been. Poured concrete in a new extension is the usual case: it needs its full cure, then a reading, then the finish.
What is on the surface? Fresh concrete has a weak, dusty skin called laitance where the fines rose to the top as it cured. Older concrete may have curing compound, paint, adhesive residue from a previous floor, oil or years of dust. None of that is something to bond to. The surface is mechanically prepared, usually by grinding, until it is sound, open and clean, then vacuumed. On a wall that has been painted the paint comes off or is tested for adhesion and keyed, depending on what it is.
Where will it crack? Every concrete slab has joints, either cut into it deliberately or formed where one pour stopped and another began. It will also hairline crack elsewhere as it shrinks. A rigid finish a few millimetres thick cannot bridge a moving crack. Live joints are carried through to the finished surface as a deliberate line, positioned where it reads as intentional. Dormant shrinkage cracks are filled and, on floors, bridged with mesh in the base coat. We would rather see the slab and decide than promise a blank surface and deliver a crack.
Microcement on concrete floors
This is the most common pairing we are asked about and the most straightforward. Microcement is applied at around three millimetres over a primer that is matched to the porosity of the concrete, with a fibreglass mesh in the base coat that shares out the stresses of drying and gives the finish some tolerance of movement. Over a power-floated slab the surface is ground first to give the primer something to hold. Over a rough or uneven slab a levelling compound goes down before the system, because microcement follows every undulation beneath it rather than filling them.
If the slab has underfloor heating, the commissioning cycle has to run before we start. We have written that sequence out in full. Skipping it is the single most common cause of a cracked microcement floor.
Venetian plaster and Marmorino on concrete walls
Polished plaster wants a flat, stable, uniformly absorbent base, which raw concrete is not. Blockwork and poured walls are rarely true enough to take a burnished finish straight off. Their absorbency also varies from patch to patch, which shows through a thin lime finish as a change in sheen. So the build-up is a bonding primer, a base coat to bring the wall flat and even out the suction, then the Venetian plaster or Marmorino coats over that. Where a concrete wall is very uneven a plasterboard lining or a full float is the honest answer. We will say so at the survey rather than try to lose a bowed wall in polish.
Exposed concrete has a look of its own that people sometimes want to keep. That is a different conversation: a sealed, honed concrete finish rather than a plaster over it. We can talk through both at a design visit.
Lime and clay plasters on concrete
The case for a breathable plaster is that it lets moisture pass through the wall. Concrete does not, so putting lime or clay over a dense concrete wall does not make the wall breathe; it gives you the texture, the depth and the healthy surface of a mineral plaster on a substrate that is managing moisture in its own way. That is fine as long as everyone understands it. Where the concrete is below ground or in contact with damp, the moisture strategy has to be resolved in the structure first, because no plaster fixes a wet wall from the room side. Lime goes over concrete with a suitable bonding coat; clay needs a clay-compatible primer and a base coat with fibre. Both need the surface clean and keyed.
Outside
Concrete rendered walls, garden walls and pool surrounds take our exterior-grade finishes, which are formulated to be frost-stable and to cope with wetting and drying. The preparation is the same: sound, clean, dry, joints respected. The difference is that the moisture reading matters even more, because an exterior wall is never as dry as an interior one and the finish has to be chosen with that in mind. Our exterior and pool systems are described here.
What we ask before quoting
How old the concrete is, whether it is a floor or a wall, whether it is power-floated, painted or bare, whether there is heating in it and any history of damp. A photograph of the surface and one of any cracks helps. From that we can usually say what the preparation will be and whether a levelling coat or a base coat is needed before the finish. The quote then reflects the substrate rather than a guess.
Our floor build-up is here, the technical hub has the substrate guidance and if you have a slab or a wall you are not sure about, send us a photograph and a postcode and our design team will be in touch.