How to Avoid Cracks in Microcement
This video demonstrates the correct technique to use to avoid cracks forming in the surface when applying microcement. Cracks in the surface that look like cracks in egg-shells usually occur when the microcement has been applied too thickly. The guidance below explains how to resolve this issue if it has already happened.
How Can I Tell if Microcement has Been Applied too Thickly?
Microcement is intended to be applied very thinly. It is at its strongest when applied no thicker than the grain size. And it doesn’t have the body for a thick application, so if it is applied thickly, it will crack in an egg shell pattern.
Cracks in the surface that look like cracks in egg-shells usually occur when the microcement has been applied too thickly. They may be across the whole surface or just in the corners where there is a build up of product.
How to Avoid Cracks in the Microcement Surface
Microcement needs to be applied in very thin coats – no thicker than the grain size. The best way of achieving this is to trowel a section down then go back over it with the trowel, blending it into the previous section and taking any excess off with your trowel as you go. Each coat should be its less than 1mm thick and completely follow the contours of the surface that its being applied to, no thicker. And you should hear the scraping of the trowel over the surface.
This especially applies to the corners, work up to internal corners, and when you reach the edge, run your finger down the corner, squashing the product into edge, then gently trowel any excess product away in both directions.
What Can I do if the Microcement has Cracked?
If you have already applied the microcement and it is too thick. It will need a really good sand back so it is completely flat, across the whole area and right into the corner.
Ideally, you need to sand it back enough until you have removed all of the cracks. You can then continue to apply the coats using the correct technique. You may need to apply additional coats of base coat or top coat, depending on what stage you are at currently.
The surface should be smooth and free from any visible signs of cracking before you seal. We wouldn’t recommend sealing the microcement until the surface is free from cracks and you are completely happy with the appearance.