Wood-floating of cement floors

Very often we are called out to give advice on the coating of cement floors. The proud new owner of the building shows us the power- floated floor. Many times the floor is as smooth and shiny as a mirror. Unfortunately this is not ideal for coating, as the surface has been rendered totally impervious to coating penetration. The first step required in term of surface preparation is then to roughen the surface so that it resembles 100 grit sand-paper. This will ensure good adhesion and penetration into the substrate, and prevent the coating delaminating from the substrate. Impact of a heavy object falling onto the coated surface, or a vehicle - even a pallet-jack – turning sharply, can cause the coating to come away from a very smooth surface if no penetration has been possible. The best method of roughening a smooth surface is by floor grinder. These can be hired by the hour from construction equipment hiring businesses. They create a lot of dust, but do the job very well. It is best to vacuum up the dust using an industrial vacuum after this process is complete. Ensure that the entire floor, including edges right up to the walls and hollow spots, are evenly abraded.

An alternative method is to acid etch the floor, but the drawbacks far outweigh the reduced cost of this approach. Strong acids are hazardous chemicals and should never handled without the correct training and Personal Protective Equipment. Acid fumes generated are highly corrosive – both to the applicators and to electrical distribution boards. The acid tends to lie in hollows on the surface, leaving high spots untreated. The floor needs to be rinsed off after etching – leaving it wet and therefore unsuitable for immediate coating. We do not sell acids used for this application due to these limitations.

 

Below is a photo of a floor topping being wood trowelled for later coating.

 

The moral of the story is that if you are screeding a floor that will be coated at a later stage, save yourself some money and have it wood-floated to a rough finish.