Preparation of the substrate:
- Determining the condition of the substrate – according to several criteria, such as levelling, strength of the surface layer, its moisture and porous structure. Cracks and other available defects are also taken into consideration. With regard to the flatness of the screed, the aim is to achieve the statutory tolerances.
- Separate the self-levelling compound from the surrounding walls and vertical structures by means of expansion strips with a minimum thickness of 5 mm.
- First, the substrate shall be primed.
- A fresh screed is applied onto the fresh primer. For this purpose, the following components are used: 1: 1 screed mix ratio of cement and 0-4 mm grain-size sand, diluted with water, 1:1 ratio (or as shown on the package)
- It is still among the most commonly used; it is considered reliable and durable. Portland cement is used as a binder material, while quartz sand, fine-grained gravel and / or expanded clay are used as a filler.
- All components are mixed with a construction mixer until a homogeneous mixture is obtained.
- Application and levelling: The smoothing is carried out with a plastic float. The thickness of traditional soluble screeds must be at least 30 mm, with variations of up to 50 mm. The thinner screeds begin to separate from the base and flake off.
There are two main disadvantages of cement-sand screeds:
a) The long amount of time required for the screed to dry and gain maximum strength.
b) The surface is not perfectly flat and an additional finishing layer is required.
- Applying tape or expanded polystyrene on the walls of the premises (5-10 mm thick), which will serve to absorb the emerging temperature stresses between the floor and the walls. They are attached to the walls with the help of a tacker.
- Setting the datum levels (“finished floor”) – level markers are placed on the walls (for example, with nails set at every 1.0-1.5 m), and on the floor – movable tripods are used throughout a squared area at fixed points every 2 x 2 m. The level that the tripods should control is set with the help of their removable screws. The datum level is selected so that the screed coating is at least 25-30 mm.
- The self-levelling screed is applied by machine or by hand.
- Additional levelling is carried out with the help of a wire fabric lath, spiked floor layer screed shoes or a spiked This is done three times, the last treatment on the surface (smoothing), starting from the inside towards the outside direction when leaving the room.
- On average 24 hours after the application, a screed surface becomes solid and you can walk on it. During this period, it must be protected from rapid drying (for example, the area should not be exposed to direct sunlight or ventilation/draught).
- Two days after applying the screed, the surface is sanded with a floor sander in order to remove the putty that has dried on the surface. This allows for faster and more even drying of the screed as well.
- Before laying parquet and other moisture-sensitive finishing coatings, the humidity of the screed should be checked.