Polished Concrete Floors in London Homes: Design, Specification & Costs 2025

POLISHED CONCRETE IS NOT PAINTED OR COATED CONCRETE — IT IS CONCRETE THAT HAS BEEN MECHANICALLY GROUND AND POLISHED TO INCREASINGLY FINE GRADES OF DIAMOND-IMPREGNATED PAD, CREATING A SURFACE THAT IS INTEGRAL TO THE CONCRETE ITSELF RATHER THAN APPLIED ON TOP.

THE POLISHED CONCRETE PROCESS:

1. CONCRETE PLACEMENT AND CURING: FRESHLY PLACED CONCRETE SLAB, MINIMUM 75MM THICK (TYPICALLY 100-125MM FOR A DOMESTIC FLOOR OVER INSULATION). MIX DESIGN IS CRITICAL: STRUCTURAL CONCRETE C25/P (MINIMUM) WITH CONTROLLED W/C RATIO (TYPICALLY 0.45-0.50) TO MINIMISE SURFACE POROSITY. COLOURED AGGREGATES OR INTEGRAL PIGMENTS (LANXESS BAYFERROX IRON OXIDE PIGMENTS) CAN BE ADDED AT MIX STAGE TO ACHIEVE SPECIFIC COLOUR TONES (GRAPHITE, WARM GREY, BUFF, TERRACOTTA). CURING: MINIMUM 28 DAYS BEFORE GRINDING BEGINS — ATTEMPTING TO POLISH TOO EARLY RISKS A WEAK, DUSTY SURFACE.

2. GRINDING (COARSE TO MEDIUM): DIAMOND-IMPREGNATED METAL-BOND DISCS (GRIT PROGRESSION: 16/30 → 50 → 100/150) REMOVE THE SURFACE LAITANCE (WEAK CEMENT-RICH TOP LAYER) AND EXPOSE THE AGGREGATE. THE AGGREGATE EXPOSURE LEVEL DETERMINES THE FINAL APPEARANCE: — CREAM POLISH (VERY LIGHT GRIND): SURFACE LAITANCE REMOVED ONLY, AGGREGATE BARELY VISIBLE — UNIFORM CEMENT-COLOUR SURFACE — SALT-AND-PEPPER (MEDIUM GRIND): 2-3MM OF CONCRETE REMOVED, AGGREGATE TIPS JUST VISIBLE — FULL AGGREGATE EXPOSURE (HEAVY GRIND): AGGREGATE FACES FULLY EXPOSED — TERRAZZO-LIKE APPEARANCE

3. DENSIFICATION: A LITHIUM SILICATE OR SODIUM SILICATE DENSIFIER (PROSOCO LITHIUM HARDENER, DEGUSSA SIKAFLOOR LITHIUMPLEX, ASHFORD FORMULA) IS APPLIED TO THE GROUND SURFACE. THE SILICATE REACTS WITH FREE CALCIUM HYDROXIDE IN THE CONCRETE TO FORM CALCIUM SILICATE HYDRATE — HARDENING THE NEAR-SURFACE ZONE AND MAKING IT MORE RESISTANT TO ABRASION AND WATER PENETRATION.

4. POLISHING (FINE TO ULTRA-FINE): REZIN BOND PADS (GRIT PROGRESSION: 200 → 400 → 800 → 1500 → 3000) REFINE THE SURFACE TO THE DESIRED SHEEN LEVEL: — MATTE (400 GRIT): SUBTLE SHEEN, HIDES MARKS WELL, MOST PRACTICAL FOR HIGH-TRAFFIC AREAS — SATIN (800 GRIT): MOST POPULAR LONDON RESIDENTIAL SPECIFICATION — SEMI-GLOSS (1500 GRIT): HIGHER REFLECTIVITY, SHOWS MARKS MORE READILY — HIGH GLOSS (3000 GRIT): MIRROR-LIKE SURFACE — IMPRESSIVE BUT HIGH MAINTENANCE IN A DOMESTIC KITCHEN

5. SEALING: A PENETRATING SEALER (PROSOCO JOINT+WIDENER GUARD, LARSEN CONCRETE GUARD, OR CADDISH SOLUTIONS NANO PROTECT) IS APPLIED TO PROTECT AGAINST WATER, OIL, AND ACIDIC FOOD STAINS (THE PRIMARY WEAKNESS OF POLISHED CONCRETE IN KITCHEN ENVIRONMENTS).

POLISHED CONCRETE IS MOST COMMONLY SPECIFIED AS A NEW SLAB IN A GROUND-FLOOR EXTENSION OR ORANGERY — COMBINING THE STRUCTURAL SLAB WITH THE FINISH FLOOR IN A SINGLE ELEMENT. THIS IS BOTH ITS KEY ADVANTAGE OVER OTHER FLOORING TYPES (NO SCREED LAYER REQUIRED) AND ITS MAIN DESIGN CHALLENGE (THE FINISH QUALITY OF THE CONCRETE CANNOT BE KNOWN UNTIL THE GRINDING REVEALS IT).

SUBBASE SPECIFICATION: — TARMAC TOPBASE TYPE 1 CRUSHED AGGREGATE, 150MM COMPACTED: PROVIDES STABLE BASE — VISQUEEN SUPER FLEXIBLE PLUS 1200 GAUGE POLYETHYLENE DPM (OR 300 MICRON): LAP 300MM AT JOINTS, TURN UP TO ABOVE FINISHED FLOOR LEVEL AT ALL EDGES — INSULATION: PIR RIGID FOAM INSULATION BELOW SLAB IS CRITICAL FOR PART L COMPLIANCE AND UFH EFFICIENCY: - CELOTEX GA4000 100MM (THERMAL CONDUCTIVITY 0.022 W/MK): U-VALUE 0.18 W/M2K BELOW SLAB - KINGSPAN THERMAFLOOR TF70 75MM: COMPARABLE PERFORMANCE, SLIGHTLY LOWER PROFILE - XTRATHERM XT/UF: COMPRESSIVE STRENGTH 200 KPA (SUITABLE FOR DOMESTIC FLOOR LOADING)

UNDERFLOOR HEATING IN POLISHED CONCRETE: POLISHED CONCRETE IS AN EXCELLENT MEDIUM FOR UNDERFLOOR HEATING — ITS THERMAL MASS STORES HEAT EFFECTIVELY AND ITS SEAMLESS SURFACE PRESENTS NO JOINTS THAT COULD BE DAMAGED BY THERMAL MOVEMENT.

RECOMMENDED UFH SYSTEM FOR POLISHED CONCRETE: — NU-HEAT LOOPSTRATE OR UPONOR MLCP 16MM PE-RT PIPE: LAID AT 100-200MM CENTRES ON TOP OF THE INSULATION BEFORE CONCRETE PLACEMENT — PIPE SUPPORTED ON MESH TIES OR REBAR CHAIRS TO HOLD AT 50-75MM FROM THE TOP OF THE SLAB — CONCRETE PLACED OVER PIPE — MINIMUM 75MM ABOVE PIPE CENTRES FOR STRUCTURAL INTEGRITY — MANIFOLD POSITIONED IN AIRING CUPBOARD OR UTILITY ROOM: DANFOSS, UPONOR, OR GIACOMINI MANIFOLD WITH INDIVIDUAL CIRCUIT CONTROLS — DO NOT COMMISSION UFH FOR HEATING UNTIL CONCRETE HAS FULLY CURED (MINIMUM 21-28 DAYS) — PREMATURE HEATING CAUSES CRACKING

CONCRETE MOVEMENT JOINTS: CONCRETE SHRINKS DURING CURING — UNCONTROLLED SHRINKAGE CRACKING APPEARS UNLESS CONTRACTION JOINTS ARE FORMED AT MAXIMUM 4M X 4M BAYS. FOR POLISHED CONCRETE FLOORS, SAW-CUT CONTROL JOINTS (6MM WIDE, 1/3 DEPTH OF SLAB) ARE FILLED WITH FLEXIBLE JOINT FILLER (FOSROC NITOFLEX, SIKA SIKAFLEX-11FC) TO MAINTAIN A WATERTIGHT SURFACE WHILE ALLOWING MOVEMENT.

POLISHED CONCRETE OFFERS A MUCH WIDER RANGE OF AESTHETIC CHOICES THAN MANY HOMEOWNERS REALISE — FROM THE STANDARD GREY CEMENT PALETTE TO CUSTOM COLOURS AND EXPOSED DECORATIVE AGGREGATE EFFECTS.

COLOUR OPTIONS:

NATURAL GREY (DEFAULT): STANDARD UK PORTLAND CEMENT (HANSON, TARMAC, CEMEX) PRODUCES THE STANDARD WARM GREY TONE MOST ASSOCIATED WITH POLISHED CONCRETE. THE EXACT SHADE VARIES SLIGHTLY BETWEEN CONCRETE POURS AND CANNOT BE PRECISELY SPECIFIED — THIS NATURAL VARIATION IS CONSIDERED PART OF THE MATERIAL'S CHARACTER.

PIGMENTED CONCRETE: LANXESS BAYFERROX IRON OXIDE PIGMENTS ADDED AT MIXING STAGE: — CHARCOAL/GRAPHITE: BAYFERROX 330 + 318 (IRON OXIDE BLACK + RED) — 1.5-3% BY WEIGHT OF CEMENT. PRODUCES DEEP GREY-CHARCOAL FLOOR WITH STRONG URBAN QUALITY. — WARM BUFF/LIMESTONE: BAYFERROX 920 (IRON OXIDE YELLOW) — PRODUCES WARM HONEY-LIMESTONE TONE. POPULAR IN PERIOD PROPERTY EXTENSIONS. — TERRACOTTA: BAYFERROX 130 (IRON OXIDE RED) — WARM TERRACOTTA TONE. POPULAR IN MEDITERRANEAN-INFLUENCED KITCHEN SPACES. CAVEAT: PIGMENTED CONCRETE STILL SHOWS TONAL VARIATION — NEVER EXPECT PERFECTLY UNIFORM COLOUR ACROSS A LARGE FLOOR.

EXPOSED AGGREGATE OPTIONS: IF AGGREGATE EXPOSURE IS THE DESIGN INTENT ("SALT-AND-PEPPER" OR FULL TERRAZZO EFFECT), THE AGGREGATE SPECIFICATION MATTERS: — WHITE LIMESTONE AGGREGATE (DOLOMITE): BRIGHT WHITE CHIPS IN GREY MATRIX — VERY POPULAR IN LONDON HIGH-SPEC EXTENSIONS — GRAVEL AGGREGATE (THAMES GRAVEL): WARM BROWN/GREY FLINT — STANDARD, NATURAL — WHITE MARBLE CHIPS (BIANCO CARRARA CRUSHED): LUXURY AGGREGATE FOR TERRAZZO-STYLE EFFECT — COLOURED GLASS AGGREGATE: ADDED AT SURFACE (NOT IN MAIN MIX) BY SEEDING ONTO FRESHLY PLACED CONCRETE — CREATES GLITTERING ACCENT POINTS IN THE POLISHED SURFACE

THE MOST COMMON CONCERN ABOUT POLISHED CONCRETE IN DOMESTIC SETTINGS IS STAINING — PARTICULARLY IN KITCHENS, WHERE RED WINE, COFFEE, OLIVE OIL, AND ACIDIC FOODS ARE PRESENT. UNDERSTANDING THE STAINING RISK AND MITIGATION STRATEGIES IS ESSENTIAL BEFORE SPECIFYING.

STAINING RISK ASSESSMENT: — RED WINE AND COFFEE: WILL STAIN UNPROTECTED POLISHED CONCRETE WITHIN MINUTES — A PENETRATING SEALER (PROSOCO JOINT GUARD OR NANOSEAL) PROVIDES A 30-MINUTE CLEAN-UP WINDOW. WIPE IMMEDIATELY. — OLIVE OIL AND COOKING OIL: PENETRATES SLOWLY — A GOOD SEALER PROVIDES ADEQUATE PROTECTION IF WIPED WITHIN 1-2 HOURS. — ACIDIC FOODS (LEMON JUICE, VINEGAR): ETCH CEMENT MATRIX IF LEFT IN PROLONGED CONTACT — EVEN SEALED SURFACES ARE NOT FULLY IMMUNE. ALWAYS WIPE IMMEDIATELY. — MUDDY FOOTPRINTS, EVERYDAY GRIME: NO ISSUE — POLISHED CONCRETE IS RESILIENT AND EASY TO CLEAN WITH A NEUTRAL PH CLEANER (FILA CLEANER OR LITHOFIN MN WASH+CLEAN).

SEALER RE-APPLICATION: PENETRATING SILANE/SILICONE SEALERS (NANOSEAL, PROSOCO) SHOULD BE REAPPLIED EVERY 2-5 YEARS DEPENDING ON TRAFFIC. TOPICAL ACRYLIC OR POLYURETHANE TOPCOATS (E.G. SIKA SIKAFLOOR 20N PURCEM TOPCOAT) CAN ALSO BE APPLIED OVER THE POLISHED SURFACE — PROVIDING HIGHER STAIN RESISTANCE BUT A LESS NATURAL, MORE PLASTIC APPEARANCE AND NEEDING FULL RE-APPLICATION WHEN WORN.

CLEANING PROTOCOL: — DAILY: VACUUM OR SWEEP TO REMOVE GRIT (GRIT PARTICLES DRAG ACROSS THE SURFACE AND MICRO-SCRATCH THE POLISH OVER TIME) — WEEKLY: MOP WITH DILUTED NEUTRAL CLEANER (FILA CLEANER 1:10 DILUTION IN WARM WATER) — AVOID: BLEACH, ACID CLEANERS, STEAM CLEANERS (ALL ATTACK THE SEALER OR CEMENT MATRIX)

POLISHED CONCRETE IN LONDON COMMANDS A SIGNIFICANT PREMIUM OVER STANDARD FLOOR FINISHES — REFLECTING THE SKILL AND EQUIPMENT REQUIRED FOR THE GRINDING AND POLISHING PROCESS.

COST GUIDE (SUPPLY AND FIT, PER M2):

NEW GROUND-FLOOR SLAB WITH POLISHED CONCRETE FINISH: — CONCRETE SLAB (100MM C25/P, STEEL MESH, DPM, INSULATION): £50-£75/M2 — POLISHING TO SATIN FINISH (800 GRIT, SEAL): £60-£95/M2 — TOTAL NEW SLAB + POLISHED FINISH: £110-£170/M2

POLISHING AN EXISTING CONCRETE SLAB (RETROSPECTIVE POLISH): — ASSESSMENT AND SURFACE PREPARATION: £15-£25/M2 — GRINDING AND POLISHING TO SATIN (800 GRIT): £55-£85/M2 — TOTAL RETROSPECTIVE POLISH: £70-£110/M2 CAVEAT: NOT ALL EXISTING SLABS ARE SUITABLE FOR POLISHING — THE CONTRACTOR MUST ASSESS SURFACE QUALITY, POROSITY, AND AGGREGATE DISTRIBUTION BEFORE QUOTING.

COMPARATIVE COSTS (PER M2, SUPPLY AND FIT): — POLISHED CONCRETE: £110-£170/M2 — PORCELAIN TILE (600X600MM QUALITY, BAL ADHESIVE): £80-£130/M2 — ENGINEERED OAK (TED TODD, BOEN 138MM): £80-£140/M2 — NATURAL STONE (KANDLA GREY SANDSTONE, MANDARIN STONE): £90-£160/M2 — VINYL/LVT (AMTICO FORM, KARNDEAN KORLOK): £40-£80/M2

TYPICAL EXTENSION EXAMPLE: 25M2 NEW REAR EXTENSION POLISHED CONCRETE FLOOR (INCLUDING INSULATION, SLAB, UFH PIPE, AND POLISHED FINISH): £5,000-£8,000 TOTAL.