This type of screed is made from calcium sulphate, sand, water and other chemicals, these materials combined form a liquid screed. This screed is poured through a hose and then levelled with dappling bars. Using this type of screed it is imperative that the floor area and edges are insulated making it fully waterproof. This type of screed is good for larger floor areas as it is quick process, however a longer drying time needs to be allowed.
Sand & Cement.
Mixed with sand, cement and water this type of screed can either come ready mixed direct from plant or it can be mixed on site. Added fibres is recommended to reduce any crack to the surface.
Sand & Cement Enhanced.
This is sand & cement screed but with added chemicals. These added chemicals improve the standard of the sand & cement screed, giving it extra strength and quicker drying time. Again, like the normal sand & cement screed, this can come ready mixed direct from plant or it can be mixed on site.
This is similar to the calcium sulphate screed, using cement rather that calcium sulphate. This type of screed is not as common as the other screeds, however, it is very fast drying and is known to be much stronger.
Expansion and Control.
Large floor areas will need to have expansion joints fitted to allow for the screed to expand and contract avoiding any cracking in the screed.
Where screed works will need to be carried out over a period of two days, day joints will be fitted to avoid any cracking.
If you are thinking about finishing the floor with marble, stone or a rigid tile, the expansion provisions need to be taken into consideration. A de bonding bedding layer can be installed on top of the screed before floor finishes are installed.
Screed and Surface Levels.
All screeds have to be installed to the British Standard level of flatness. A gap under a straightedge anywhere on the surface cannot be more than:
Reinforcing Mesh / Fibres.
D49 mesh or fibres are used to reinforce screed (sand cement types) to avoid cracking.
Screed Treatment for Floor Finishes.
A sealer may be required before installing your floor finish. Be sure to check with the floor manufacturer before hand.