Concrete Finishes: Exposed, Board-Marked and Polished

Concrete is the most common structural material in Indian buildings and, for most of its life, the most hidden. It is cast, plastered, putty-coated, painted, tiled and clad until nobody can tell what holds the building up. Over the last decade that has changed. Homeowners ask for a raw concrete ceiling in the living room, cafés want board-marked walls, offices ask for polished concrete floors, and architects across India continue the tradition of exposed concrete established here in the 1950s and 1960s. Concrete, it turns out, can be a finish.

But exposed concrete is unforgiving. With plaster, a mistake in the formwork is hidden by 12–20 mm of sand and cement; with exposed concrete, every tie hole, joint, honeycomb, colour change and grout leak is the final surface. Many Indian projects that set out to achieve exposed concrete end up painting it grey, or covering it with a concrete-effect texture, because nobody planned the pour as a finish. The other common failure is the opposite: a beautiful wall that stains, grows algae and lets in water after two monsoons, because it was never sealed or detailed for rain.

This article explains the three main families of concrete finish — exposed (fair-face) concrete, board-marked concrete and polished concrete — how each is made, what to specify, what goes wrong, and what each costs, with indicative October 2026 prices consistent with this site's other materials guides. It also compares them with the lookalikes: microcement, cleaned and sealed slabs and concrete-effect paints.

From Roman vaults to Indian modernism

Concrete itself is ancient. Roman builders used a concrete of lime, volcanic ash and rubble to build vaults and domes, the most famous being the Pantheon in Rome, completed in the second century and still standing. Modern concrete begins with Portland cement, patented in England by Joseph Aspdin in 1824, and with reinforced concrete, developed in France in the second half of the nineteenth century. For most of its first century, reinforced concrete was treated as a structure to be hidden behind stone, brick or render.

The idea of concrete as a finished surface owes most to Le Corbusier, who used the French term béton brut — raw concrete — for the board-marked concrete of the Unité d'Habitation in Marseille, completed in 1952. India then became one of the great laboratories of exposed concrete. Le Corbusier's Capitol Complex at Chandigarh, and his buildings in Ahmedabad — the Mill Owners' Association building and Villa Shodhan, among others, both from the 1950s — showed board-marked concrete, deep sun-breakers and sculptural roofs in an Indian climate. The Chandigarh Capitol Complex is part of the UNESCO World Heritage listing of Le Corbusier's architectural work, inscribed in 2016. A generation of Indian architects, including Balkrishna Doshi and Charles Correa, went on to build in exposed concrete and brick across the country.

The finish families at a glance

It helps to separate finishes by when the surface is made. Fair-face and board-marked concrete get their surface from the formwork at the moment of casting; nothing is added afterwards except cleaning, minor repairs and a sealer. Power-floated and polished concrete get their surface from mechanical work on a horizontal slab — trowelling while it sets, or grinding after it hardens. Treated finishes such as sandblasting and bush-hammering remove the outer skin of hardened concrete to expose aggregate. Coatings such as microcement, concrete-effect plaster and paint are not concrete finishes at all: they are thin layers that look like concrete.

Exposed concrete starts with the mix

Concrete that will be seen must first be good structural concrete. In India that means design to IS 456, which sets minimum grades by exposure — M20 for mild, M25 for moderate and M30 for severe exposure, with higher grades for very severe and extreme conditions — and minimum cover to reinforcement that increases with exposure, from about 20 mm in mild conditions up to 75 mm in extreme ones. The structural engineer fixes these. Exposed concrete adds a second set of requirements: consistent colour, a dense skin and a surface free from honeycombing and large blowholes.

Consistency is the key word. Every pour for one visible surface should use cement from the same source and, ideally, the same batch, the same sand and aggregate, the same admixture and the same water–cement ratio, because each of these changes the colour. A ready-mix plant that supplies the whole job from one source is easier to control than site mixing. Fine materials matter: a mix with enough fines and a well-graded aggregate fills the face of the formwork without leaving voids. Admixtures that improve workability without adding water — plasticisers and superplasticisers — make dense, well-compacted surfaces easier to achieve.

Fair-face concrete: formwork, ties and joints

Smooth fair-face concrete is usually cast against film-faced plywood — birch or hardwood plywood coated with a phenolic film — or against steel forms. Film-faced plywood in India is commonly 12–18 mm thick in 1220 × 2440 mm sheets. Each sheet joint and each form tie leaves a mark, so the formwork must be drawn like a facade: sheet layout, tie hole grid, construction joints and chamfers are designed in elevation and agreed before carpentry starts. A typical layout uses whole sheets in a regular pattern with tie holes at regular centres, often 600–900 mm, aligned with sheet joints. Tie holes are left as neat recessed cones or plugged with matching mortar or plastic caps — the choice is part of the design.

Edges need care. A sharp 90-degree corner on concrete chips easily during stripping and use, so exposed edges are usually given a small chamfer of about 15–20 mm, formed by a triangular fillet in the formwork. Construction joints — where one pour meets the next — should run in straight lines along planned rebates or reveals, not wherever the pour happened to stop. Form joints must be tight and sealed with foam tape or sealant, because grout leaking through a gap leaves dark sand-streaked lines and honeycombing. A release agent, applied thinly and evenly, protects the face and helps the forms strip cleanly. Formwork and falsework design follow general guidance such as IS 14687, and must be checked by the engineer for the pressure of the wet concrete, which rises with pour rate and height.

Board-marked concrete: timber that leaves its memory

Board-marked concrete is cast against formwork lined with timber planks, so that the grain, knots and joints of the boards are imprinted in the surface. The planks are usually sawn softwood or pine, about 75–150 mm wide and 18–25 mm thick. Rough-sawn or sandblasted boards give a deep grain; planed boards give a softer pattern. Board widths can be uniform for a calm, striped wall, or mixed for a more rustic look, and boards can run horizontally — the common choice, which emphasises the length of a wall — or vertically, which suits columns and tall narrow walls.

New timber absorbs water and cement paste unevenly, which makes the first casts patchy and darker. Contractors therefore season new boards before the first pour, typically by brushing on a cement slurry and cleaning it off, or by a first use on a hidden element, and they apply a release agent before every pour. Boards are normally fixed to a plywood backing so that the formwork remains stiff and true; joints between boards are kept tight or deliberately formed with a small V-groove so that leaks do not create random dark streaks. The number of reuses is limited — the grain wears and the faces change after a few pours — so a large wall may need a fresh set of boards, which should be prepared the same way.

Treated surfaces: sandblasted and bush-hammered

Where a softer, stone-like surface is wanted, hardened concrete can be sandblasted, which removes the cement skin and reveals fine aggregate, or bush-hammered, which chips the surface with a pointed hammer head to expose coarse aggregate in a rough, granite-like texture. Both hide small variations in colour and minor blemishes, and both make a surface less slippery, but they also reduce effective cover slightly, so the engineer should allow for the depth removed. They work well on plinths, external walls and boundary walls, where a crisp formwork finish would show every knock.

Polished concrete floors

A polished concrete floor is a concrete slab, or a concrete topping laid on a slab, that has been ground flat with diamond tooling, hardened with a chemical densifier, and polished through progressively finer grits until it reaches the required sheen. Unlike a coating, the polish is in the concrete itself. Done well, it is hard-wearing, easy to clean and long-lasting; done badly — on a weak, wet or uneven slab — it dusts, stains and shows every crack.

The process follows a clear sequence. The slab should be well compacted and power-floated, and is usually left to cure for about 28 days before grinding. Coarse metal-bonded diamonds, typically around 30–40 grit, grind the surface flat and expose the chosen level of aggregate. Successive passes with finer metal and then resin-bonded diamonds remove the scratches of the previous pass. A lithium or sodium silicate densifier is applied after the early grinding stages; it reacts with the free lime in the cement to harden and tighten the surface. Polishing continues through finer grits — commonly up to 400 for a matte or satin finish, 800 for a semi-gloss and 1500–3000 for high gloss — and a penetrating sealer or guard protects against stains.

Polished concrete in Indian homes raises three practical issues. First, cracks: concrete shrinks as it dries, and a floor without properly spaced control joints will crack where it chooses, not where the designer would like. Joint spacing is commonly kept to about 24–36 times the slab thickness, so a 100 mm slab or topping gets bays of about 2.4–3.6 m, cut to about a quarter of its depth as early as the concrete allows. Second, stains: oil, turmeric, haldi-kumkum and acids such as lemon juice and vinegar etch or stain an unsealed polished floor, so kitchens and pooja areas need a good guard sealer and quick cleaning. Third, slip: high-gloss concrete is slippery when wet, so bathrooms, verandahs and entrances should use a honed or satin finish with anti-slip treatment.

Exposed concrete in the Indian climate

Exposed concrete behaves differently in Surat's humidity, Ahmedabad's dry heat, Mumbai's coastal air and Delhi's dust. In hot-humid and coastal cities, rain-washed external concrete grows algae and fungus in dark streaks below every ledge, and chlorides from sea air can reach the reinforcement if cover is thin or the concrete porous, leading to rust stains and spalling. In all climates, carbon dioxide from the air slowly carbonates concrete from the surface inward, reducing the alkalinity that protects the steel; dense concrete and adequate cover slow this down. Exposed roofs and west walls also absorb and re-radiate heat — concrete has high thermal mass — so an exposed concrete roof needs insulation above it, and a west wall benefits from shading.

The answers are well known. Detail the concrete for rain: drips under every projection, sloping tops on parapets and sills, and no flat ledges that collect water and dirt. Treat the exposed surface with a breathable, penetrating silane or siloxane water repellent, which reduces water absorption without changing the look much; anti-carbonation coatings add protection where the specification calls for them. Inside, use a penetrating sealer that resists stains and fingerprints. Repair tie holes and minor defects with colour-matched mortar trials before the real work. And accept that exposed concrete is a living surface: it darkens when wet and lightens as it dries, and that variation is part of its character.

Costs and how to read a quotation

Exposed concrete is usually priced as an extra over ordinary RCC, because the structure would be built anyway. The extra pays for better formwork, more carpentry and planning time, ties and cones, more careful pouring and compaction, mock-ups, cleaning, repairs and sealing. Polished floors are priced per square foot of floor ground and polished, usually excluding the slab itself. All ranges below are indicative October 2026 figures for Indian cities; several are new to this site and are given as wide bands for that reason. They vary with area, height, access, specification and the contractor's experience — and exposed-concrete experience is worth paying for.

A worked example helps. A 4.2 m long, 3.0 m high board-marked feature wall in a living room has about 136 sq ft of exposed surface. At ₹150–400 per sq ft extra over ordinary RCC, the board-marked finish costs about ₹20,000–54,000 more than a plain wall that would then be plastered and painted — and it saves the plaster and paint. A 600 sq ft living–dining floor in salt-and-pepper polished concrete at ₹120–300 per sq ft costs about ₹72,000–1,80,000 for grinding, densifying, polishing and sealing, on top of a suitable slab or topping. For comparison, the same floor in laid vitrified tile at about ₹85–160 per sq ft would cost about ₹51,000–96,000.

Where concrete finishes are going

Three developments are shaping concrete finishes in India. Better materials — ready-mix concrete with consistent quality, superplasticisers, self-compacting concrete for congested or complex forms, and factory-made precast and GFRC panels — make high-quality exposed surfaces more achievable than in the past. Lower-carbon concrete is gaining attention, using blended cements with fly ash or slag and optimised mixes, though these can change colour and curing needs, so they must be in the mock-up. And thin concrete-look systems, from microcement to concrete-effect plasters, keep improving, which lets designers put the concrete look where real concrete would be impractical — while real exposed concrete is reserved for the places where its honesty matters.

Rules for specifying exposed and polished concrete

• Decide which surfaces will be exposed before the structural drawings are issued, and draw them as finishes.
• Draw the formwork elevation: sheet or board layout, tie holes, construction joints and chamfers.
• Insist on a mock-up panel with the real formwork, mix, release agent and curing, and keep it as the reference.
• Use one cement source, one aggregate source and one mix for each visible element.
• Get workability from plasticisers, not water, and compact with vibrators at close centres.
• Cure for at least 7 days (OPC) or 10 days (blended cement or hot weather), keeping exposed faces evenly moist.
• For polished floors, start with a well-compacted, power-floated slab, plan control joints at 24–36 × thickness and wait about 28 days before grinding.
• Seal every exposed surface: silane/siloxane water repellent outside, penetrating stain guard inside.
• Detail drips and sloping tops so rainwater never runs down the face of external concrete.
• Hire a contractor who has built exposed concrete before, and visit their completed work.

Frequently asked questions

Is exposed concrete good for Indian homes?

It can be, if it is planned as a finish and protected. Inside, an exposed ceiling or feature wall is durable and low-maintenance once sealed. Outside, especially in humid or coastal cities, it needs good cover and grade, drips and sloped tops, and a water-repellent treatment, or it will streak and stain. Exposed concrete roofs must be insulated above, because concrete absorbs and re-radiates heat.

What is the difference between polished concrete and microcement?

Polished concrete is the concrete slab itself, ground and polished with diamond tooling and hardened with a densifier. Microcement is a 2–3 mm decorative coating of polymer-modified cement applied over an existing surface and sealed. Polished concrete needs a suitable new slab; microcement can go over tiles, screeds and walls, but depends heavily on the base and the applicator.

How much does a polished concrete floor cost in India?

Indicatively, in October 2026, about ₹120–300 per sq ft for grinding, densifying, polishing and sealing a suitable slab, and about ₹180–350 per sq ft for an exposed-aggregate finish, excluding the slab or topping itself. Prices vary with area, flatness, gloss level and city.

Can an existing RCC slab or wall be made into exposed concrete?

Sometimes. Removing plaster from an existing slab or wall reveals concrete that was never cast to be seen: expect tie marks, patches, honeycombing and colour changes. It can be cleaned, repaired and sealed for an honest industrial look at about ₹40–100 per sq ft, but it will not look like planned fair-face concrete. Check with a structural engineer before removing plaster near damaged or corroded areas.

Does polished concrete crack?

All concrete shrinks as it dries, so cracks are likely unless control joints are planned. Joints at about 24–36 times the slab thickness, cut early to about a quarter of the depth, together with good curing, keep cracks mostly in the joints. Hairline cracks may still appear and are usually considered part of the material's character.