Microcement itself rarely cracks; the substrate beneath it does. A thin coating at 0.3–5.5 mm follows every movement in its base, so cracked screeds, hollow tiles and skipped mesh reappear as lines in the finish. Correct preparation, embedded fibreglass mesh and respected movement joints prevent almost all of it.
Why the question keeps being asked
Search for microcement and cracking appears in the first row of questions. The concern is reasonable: a seamless finish a few millimetres thick, spread across whole floors, invites the suspicion that it must split somewhere.
Most of the evidence behind the worry comes from three places — DIY applications, cheap products applied outside their data sheets, and substrates that were never surveyed. None of those is an argument about the material. They are arguments about how it was used.
The honest answer has two halves: why cracks happen, and what a repair really looks like when they do. This article covers both, because a specifier deserves the second half as much as the first.
The material is not the usual culprit
Cemher's Microdur Plus records an adhesion strength above 6 N/mm², compressive strength Class C50 and impact resistance above 25.5 Nm — figures from EN test standards, not brochure copy. A correctly built system is a hard, well-bonded skin, and fibreglass mesh is embedded in the first base coat as standard.
What the material cannot do is resist geometry. At 0.3 to 5.5 mm applied thickness it is a finish, not a structural layer, and it follows whatever the substrate does — a point we make just as bluntly about thickness. If the base moves, the finish reports it.
That is the correct diagnosis for nearly every cracked microcement photograph online: a substrate crack telegraphing through a thin coating. The line was already in the building. The finish merely published it.
The real causes: substrate, preparation, system
Substrate movement is the first cause. Green concrete still shrinking, screeds that were never cured, hollow or drummy tiles, boards that flex underfoot — each moves more than a bonded finish can absorb. The survey exists to catch them before the first coat, not after.
Poor preparation is the second. Dust, grease, paint residues and damp all weaken the bond, and a finish that has partially debonded will crack at the boundary of the loose area. Substrate condition, consolidation and dryness are stated requirements on the data sheet, not suggestions.
The wrong system is the third. Applying outside the 10 to 30°C window, skipping the mesh, rushing coats, or using a product somewhere its limits exclude — a non-immersion microcement in a pool being the classic — produces failures the material was never going to survive. Choosing correctly is covered across what microcement is and is microcement waterproof.
Mesh, joints and the discipline that prevents cracks
The fibreglass mesh embedded in the first base coat distributes stress so that small, inevitable micro-movements never concentrate into a visible line. It is part of the Cemher build-up, not an optional extra, and its absence is one of the commonest findings in failed work by others.
Movement joints are the second discipline. Where the structure has a joint, the finish must respect it — carried through and expressed, never plastered over. A movement joint hidden under a seamless finish does not stop moving; it simply chooses where the crack will be.
The rest is sequencing: coats at their stated intervals, sanding between, sealing 24 to 48 hours after hardening at below 5% moisture. None of it is exotic. All of it is why professional installation matters more with microcement than with almost any finish, on floors especially.
Wet areas: where moisture and movement meet
Bathrooms add one more mechanism. If water reaches the substrate from behind — a missing membrane, an unsealed junction — the base can swell, soften or move, and the finish above it cracks or delaminates. The failure gets blamed on the microcement; the cause was the tanking.
That is why a wet room is specified as a system: membrane beneath, waterproof-in-mass finish above, sealed face on top. The full build-up is in microcement bathrooms.
Going over existing tiles deserves the same caution. Sound, well-bonded tile is an acceptable substrate for Microdur Plus; hollow tile is a crack waiting for a finish. The tap test and what follows it are covered in microcement over tiles.
The honest repair story
No cementitious finish repairs invisibly, and it would be dishonest to claim otherwise. A hairline that appears over a substrate movement can be filled and re-sealed, but a patch in the middle of a panel will read as a patch — colour is mixed per batch, and a small area trowelled later never quite matches a large area trowelled earlier.
The professional approach is to repair to natural breaks. A wall panel, a floor zone between joints or thresholds can be re-coated as a whole, and the new surface then reads as one plane again. That is a manageable, local intervention — not a rip-out.
This is one genuine difference from clay plaster, which re-wets and reworks seamlessly, as we describe in what clay plaster is. Microcement trades that repairability for hardness, water resistance and floors. Every finish is a set of trade-offs; this is microcement's.
It is also worth saying what repair is usually for. On a well-prepared substrate, what needs attention over the years is usually the sealer — a scratch or a stain — rather than the microcement itself: face maintenance rather than failure.
Specifying crack-resistant microcement in Saudi Arabia
Conmarble supplies and installs the Cemher microcement systems with our own applicators, and the crack question is settled where it should be: at the substrate survey, before anything is mixed. At King Fahad Cultural Centre in Riyadh the finish runs across atrium floors, stairs and the grand hall — large, trafficked planes that depend on that discipline.
If a substrate worries you, send photographs and drawings through the enquire page, or message the Riyadh office on WhatsApp at +966 56 808 8273, and we will tell you plainly whether it is ready. Wellness, in Every Surface.