Crack next to expation joint

Most people I’ve spoken to regarding their CemCrete of Weber coloured/decorative cement project are worried about the product cracking once installed.

There are two reasons for cracks forming in a cementitious finish:

• Cracks forming as a result of movement in the substrate – i.e. the floor slab or the wall moving because of inadequate reinforcing of the structure or excessive ground movement, unsupported or badly supported roofing structures, etc. and
• Dry-shrinkage of the newly applied finish; where the product loses moisture too quickly because of heat or direct sunlight, inadequate curing, or the use of too much water during the mixing process. In this case the finish itself shrinks as it dries out, and creates cracks.

Obvious structural crack. Wht do you do to fix this?

In the case of movement in the substrate, there is very little that can be done about it, apart from reinforcing the substrate itself by utilising some engineering methodologies like tying the parapet walls together to keep the structure from pushing out, or reinforcing the foundation – all of these things are extremely difficult and expensive once the structure has been built.

The fact of the matter is; any finish – whether it’s paint or tiles or cement or whatever – gets ‘stuck’ onto the structure in some way, and if there is movement inside the structure, the finish will crack.

When it comes to dry-shrinkage, the game changes a little. Here it depends on what time of the day the product was applied; whether it was applied in direct sunlight, or in the shade; whether it was cured during the initial drying period; whether the applicator could have put certain additives into the product to give it a little more flexibility and to fill the ’molecular voids’ left by the evaporating moisture; and a whole list of other factors.

How do you avoid this from happening?

At Creative Touches we take all of these factors into account when looking at your proposal, as well as during your project. And we communicate this with you along the way.

As a standard, we use Poly propylene fibres inside our screeds, as well as latex to allow for some movement. We also don’t use usual river sand as the screed, but crusher dust that does not contain any clay. We use certain membranes to decrease the chances of structural movement creating cracks in the finish – especially when we are aware of structural problems – and we always, always, always cure our products.

To conclude, it is not possible to entirely avoid cracks, it is however possible to greatly reduce the occurrence of cracks, and to minimise their effect.

Just another reason why your journey should start with us.

CemCrete CreteCote floor done by Creative Touches

About the author: Michael Pretorius is an experienced interior designer and owner of Creative Touches interiors. For more information you can visit www.creativetouches.co.za or call him directly on 082-392-3336