Microcement
Thin cementitious coating for seamless floor and wall finishes; requires stable substrate and sealing for durability.
What is microcement, and how does it differ from a polished-concrete finish?
Microcement is a thin cementitious coating (2-3 mm) composed of Portland cement, fine sand, polymers, and pigments, mixed on site and troweled onto prepared substrates. Unlike a polished concrete floor, which grinds an existing structural slab over weeks, microcement is an overlay that works on screeds, tiles, or wood subfloors. Both create a seamless, industrial aesthetic, but microcement is faster, cheaper, and lighter, ideal for retrofits. Terrazzo offers similar aesthetics but is heavier; microcement excels where speed or weight is a constraint.
What substrate preparation is critical for microcement success?
Substrate preparation is the leading cause of failure if skipped and determines whether microcement will adhere or delaminate. The substrate must be solid, stable, dust-free, and dry. Over a screed, the substrate must cure for at least 3-4 weeks and be bone-dry; any residual moisture causes bubbling and edge delamination. All existing cracks must be injected with epoxy or cementitious repair mortar and allowed to stabilize; cracks will propagate through the microcement if the underlying substrate continues to move. Paint, wax, sealers, and any contaminants must be stripped by grinding or chemical stripping; dust remaining on the surface prevents the primer from bonding properly. A substrate-specific primer (typically polyurethane or epoxy) is then applied as the critical adhesion interface; this step is non-negotiable and is the single largest factor in adhesion success. Environmental conditions matter: apply only in 10-25°C air temperature and 40-75% humidity; above 75% humidity or below 10°C, the primer and microcement cure too slowly or incompletely, and adhesion fails.
How does microcement perform over underfloor heating?
Microcement and radiant floor heating are compatible if thermal cycling is completed first. The heated screed must undergo 4-6 weeks of cycles at operating temperature (20-22°C) before microcement is applied, allowing the substrate to reach final dimensions. If applied to a thermally unsettled screed, temperature-driven expansion and contraction cause cracking. Avoid cooling below 15°C or heating above 27°C during the first 7-10 days of curing. Once cured, normal radiant cycles pose no risk; the screed's thermal mass insulates the thin finish. For passive-house projects with stable heating, integration is smooth; conventionally heated homes with seasonal temperature swings carry higher cracking risk.
Why does microcement crack over screeds, and how is cracking minimized?
Cracking results from substrate movement: screeds undergo micro-movements months after curing, especially with underfloor heating or moisture fluctuations. When the screed expands or contracts even 0.5 mm over 5 m, the rigid microcement cannot absorb the strain and fails in tension. Thermal gradients create differential shrinkage and stress concentrations. Cracking is minimized by: (1) waiting for full substrate stabilization, (2) completing thermal cycles before application, (3) applying control joints every 4-5 m, (4) using flexible primer and formulations, and (5) maintaining stable curing conditions. Hairline cracks following joint patterns are cosmetic; large irregular cracks indicate poor substrate stability or primer adhesion.
How is microcement sealed, and why is sealing mandatory?
Unsealed microcement absorbs water, oils, and dyes, causing permanent staining and degradation. Sealing begins 2-3 weeks after application, once the finish has fully cured. Penetrating sealers (polyurethane, epoxy, or acrylic) are applied in two coats, filling micro-voids and creating a water-repellent barrier. Solvent-based sealers resist stains better but release VOCs; water-based options are lower-odour but slightly less durable. In kitchens and bathrooms, hard-wearing polyurethane is added for scratch protection. Sealed surfaces tolerate spills and humidity but are not waterproof; wet rooms are not recommended. Resealing every 2-3 years in high-traffic areas or 5 years in low-traffic spaces maintains protection and restores non-slip grip.
How does microcement compare to polished concrete and terrazzo as a finish?
All three offer seamless, monolithic aesthetics but differ in cost, speed, and durability. Polished concrete requires an existing structural slab ground over weeks; capital-intensive and slow. Microcement is applied as an overlay in 1-2 weeks and works on any stable substrate. Terrazzo is elegant but heavier and costlier; repairs are labour-intensive. Polished concrete and terrazzo last 20-30 years in residential use; microcement lasts 10-15 years. Microcement excels for retrofits and tight budgets; polished concrete or terrazzo suit new projects where durability justifies cost.
What is the realistic lifespan and maintenance of a microcement finish?
In residential use, microcement remains attractive for 10-15 years; the sealer degrades before the cement itself. Heavy-traffic areas show wear in 5-7 years; low-traffic bedrooms may exceed 15-20 years with regular resealing every 3-5 years. Maintenance is simple: clean weekly with pH-neutral soap; avoid acidic or caustic products. Reseal when water no longer beads on the surface. Unlike vinyl or cork, microcement cannot be sanded or refinished; damaged sections must be removed and reapplied, which is expensive. For owners willing to maintain sealing schedules, microcement delivers an honest, minimalist aesthetic at moderate cost.
| Property | Microcement | Polished Concrete | Terrazzo |
|---|---|---|---|
| Thickness | 2-3 mm | Full slab (150+ mm) | 10-20 mm |
| Installation time | 1-2 weeks | 4-6 weeks (slab + polishing) | 3-4 weeks |
| Can overlay existing surfaces | Yes | No | No |
| Relative cost per m2 | 100% (baseline) | 150-200% | 120-180% |
| Lifespan (residential) | 10-15 years | 20-30 years | 20-30 years |
| Requires sealing | Yes, mandatory | Yes | Yes |
| Best suited for | Retrofits, speed, budget | New construction, durability | Prestige, custom aesthetics |
| Critical Substrate Requirement | Must Meet | Failure Consequence |
|---|---|---|
| Concrete or screed age | Minimum 4 weeks, fully stable | Continued shrinkage telegraphs through, causing cracking |
| Moisture content | Dry (≤ 2% by calcium carbide) | Trapped moisture causes bubbling and delamination |
| Existing cracks | Repaired, injected, substrate stable | Cracks propagate through microcement |
| Surface cleanliness | Dust-free, no paint or sealers | Contamination prevents primer adhesion, causes delamination |
| Thermal cycling (if heated) | 4-6 weeks at 20-22°C before application | Thermal movement after application causes cracking |
| Primer application | Yes; substrate-specific per manufacturer | No primer guarantees delamination and failure |
Frequently asked questions
- What is microcement made of, and how long does it take to cure?
- Microcement is Portland cement, fine aggregate, polymers, and pigments mixed on site with water. It sets in 24-48 hours and reaches full strength in 5-7 days. The polymer content provides flexibility and adhesion that plain cement lacks.
- Can microcement be installed over a moving or cracked screed?
- No. Microcement demands a stable substrate. Any movement from thermal expansion, deflection, or cracks will telegraph through and cause the microcement to crack and delaminate. The substrate must stabilize for at least 3-4 weeks before application; cracks must be injected and repaired.
- Does microcement work with underfloor heating?
- Yes, but the heated screed must thermally cycle at operating temperature (20-22°C) for 4-6 weeks before application. If applied too soon, thermal movement causes cracking. Avoid temperature swings below 15°C or above 27°C during the first 7-10 days of curing.
- How often does microcement need resealing?
- High-traffic kitchens need resealing every 2-3 years; low-traffic spaces every 3-5 years. The sealer degrades before the cement itself. Inspect annually and reseal when water no longer beads on the surface. This is essential maintenance, not optional.
- What damages or stains microcement most easily?
- Acidic and oily substances (vinegar, wine, oils, grease) etch or stain if not sealed. Scratches show readily on matte finishes. While durable for normal residential use, high-wear areas demand frequent resealing. It is less forgiving than sealed stone or tile.
- Is microcement suitable for kitchens, bathrooms, and wet rooms?
- With proper sealing, kitchens work well if resealed every 2-3 years. Bathrooms are challenging due to moisture; wet rooms are not recommended. For comparison, a polished concrete floor or terrazzo offer similar aesthetics with less maintenance.