The method for installing ceramic tiles depends strictly on the type of surface on which the flooring is being laid.
There are two main types of base:
1. cement surfaces
2. existing flooring
The first step is to prepare screed, a horizontal element made from water, cement and inert minerals. The flatter and more high quality the screed, the greater the aesthetic result and the durability of the floor.
How do you prepare screed?
Bonding screed Elements that bond to the supporting surface, ideal if there is only a thin surface on which to place the screed (less than 35mm). It is advisable to place an adhesive grout on the surface (synthetic rubber latex and the binding agent used to make the screed). The fresh screed mix will be placed on the fresh grout (this is called "fresh on fresh"). Isolating screed Screed that lies above an isolating layer, attached to the supporting structure; has a thickness of 35/40mm. Isolating screed is a preferred solution to adhesive screed, provided it is thick enough, as it is unaffected by bending and deformation of the supporting structure. First, the isolating layer must be laid; then one layer of the compressible material along the walls (such as expanded polystyrene). In order to create floating isolating screed, an electro-welded mesh will have to be inserted through the centre due to the low mechanical strength and the high compressibility of the isolating material. To make heated isolating screed, add super-plasticising admixtures to the screed (or special cement binders/premixed mortar), that are designed to incorporate heating coils. How to spread the screed? Properly spreading the screed is essential to getting a flat layer to lay the new tiles on. If the screed contains pipes, it is necessary to guarantee a thickness of no less than 2.5 cm; place a wire mesh over the pipes to avoid cracks. After making levelling strips, spread the screed compress and level the mix. Finish spreading the surface with the necessary tools, being careful not to overdo it in order to avoid problems such as bleeding.
Before laying the new tiles, check that the supporting surface is:
- resistant to mechanical stress, guaranteed by solidity across the whole depth of the screed.
- cleaning: it will be necessary to remove any elements that could compromise the bonding of the new flooring (grease, oil, plaster, paint, etc.).
- no cracks, it is imperative to seal any cracks/splits that may be present in the screed before laying.
- left to dry, i.e. the screed must have completed its hygrometric shrinking (period of 7-10 days per cm thick) before laying, to avoid creating cracks after laying which could cause it to detach or break.
Make sure that the existing flooring is free of cracks and properly bonded to the underlying surface. Then clean the flooring well with a solution of caustic soda and water or a dilute alkaline detergent. Decide if any sanding is necessary.
If the old floor is not perfectly bonded to the underlying surface, it is essential to remove the tiles that are about to detach, and to seal the cracks with a filler. Then clean the existing flooring and fill the cracks created with a fast-setting cement compound.