What Goes Wrong With Microcement, and How to Avoid It

Almost everything that goes wrong with microcement traces back to one of three things: the wrong system, poor preparation, or rushing a step that had a window. Here is the list, with what causes each and whether you can recover it.

Old grout lines showing through

Cause. Core applied straight over tile. Without the mesh and build coat there is nothing to absorb the difference between tile and joint, so the grid reappears as the finish settles.

Prevention. Reinforced over tile, every time. That is what the build coat is for.

Fix. Difficult. Usually means building up properly over the top. Prevention is much cheaper.

Cracking

Cause. Movement underneath reaching the surface — a flexing subfloor, a substrate joint bridged with a rigid finish, mesh omitted where it was needed, or a drummy tile left in place.

Prevention. Deal with deflection before you start, exactly as you would before tiling. Carry structural movement joints through to the finish rather than covering them. Use Reinforced wherever the rules say to.

Fix. A hairline can be repaired. A crack that is still moving will come back until the movement is dealt with, so find the cause first.

Trowel marks and unevenness

Cause. Working past the material’s window, inconsistent pressure, or trying to fix a section that has already started to set.

Prevention. Plan the room before you open a pail — where you start, where you finish, where a natural break falls. Do a sample board first so your hand knows the material before the wall does.

Fix. Usually yes, by sanding and reworking. This is the most recoverable problem on the list, which is why walls are a good place to learn.

Staining

Cause. Sealer skipped, rushed, applied too thin, or not right for the traffic. Remember what the sealer does: the microcement itself is waterproof, but the sealer is what protects the finish from staining and cleaning products.

Prevention. Two coats of sealer on every job, no exceptions, and do not do it at the end of a long day.

Fix. Often recoverable depending on what caused the stain and how deep it went.

Patchy or inconsistent colour

Cause. Batches mixed differently, inconsistent water, or coats applied at different states of dryness.

Prevention. Mix the same way every time and keep a record of exactly what you did. Our mixing ratio calculator is there to keep you honest about it.

Fix. Another coat, mixed consistently.

Debonding or lifting

Cause. Preparation. A contaminated surface, a missed primer, drummy tile left in place, or dust not removed before priming.

Prevention. Clean, sound, primed. Every drummy tile out and filled before you start.

Fix. Cut it out and redo that area properly. There is no shortcut.

A floor that feels slippery

Cause. Finish and sealer chosen without thinking about where they were going. This matters most on a shower floor and on a pool deck.

Prevention. Tell us where the surface is going before you order rather than using the same specification you would use on an interior floor.

The pattern

Five of the seven above are decided before any microcement comes out of the pail. Prep and system choice are the job. The trowel work is the part everybody worries about and the part that is most recoverable.

Which system you need

Core is primer, microcement, sealer. It covers interior walls, bare concrete floors and indoor fireplaces.

Reinforced adds fiberglass mesh bedded into a structural build coat. You need it for anything wet, anything outdoors, and any floor that is not bare concrete. The mesh is what stops movement underneath reaching your finish.

Microvella ships late 2026. Join the waitlist and we will email you the day it is ready to order.

Related: What it can go over · Microcement for painters · Shop the full system