Levelling screeds are high quality products designed for internal flooring applications from modest house extensions and self builds to major commercial, residential, education and healthcare developments.
These types of screeds can be used as a monolithic topping to structural concrete or more commonly as a bonded, unbonded or floating construction.
Levelling screeds that are cement based are typically described or specified according to their volume of cement to aggregate (0/4 – sharp sand) for example 1:3, 1:4 and 1:5. These products have a lower water content that most cement based mixes (concrete and mortar) in order that they can be formed to the required level and finished to give a durable and flat / planar surface that is ready to receive the final flooring finish.
Levelling screeds are typically applied to a ground supported concrete slab or precast concrete floor units. Increasingly these screeds are laid as floating floors onto thermal or acoustic insulation.
Screeds are produced under tightly controlled factory conditions; they are delivered to site ready to use and sufficiently retarded. They are produced with guaranteed mix proportions and thoroughly mixed to overcome any potential problems relating to site mixing.
Cement-based screeds can be finished to suite the proceeding floor finish with either a roughened surface or a smoother polished surface. Increasingly these screeds are used in conjunction with underfloor heating systems and services such as IT cabling in which the pipes and cable ducts are embedded in the screed. Cement based screeds can benefit from the inclusion of steel mesh fabric or polypropylene fibres to control drying shrinkage characteristics.
Pumpable self-smoothing screed, based on calcium sulphate of either the hemi-dydrate or anhydrite form, can provide significant additional benefits including:
For further information on screed availability and technical details contact an MPA Mortar member.
The type of screeding mortar used will depend on the required strength and end use. Levelling screeds are designed for a number of applications and to receive a final flooring, the thickness of the screed is governed by the method of construction being used. To achieve the optimum performance from a levelling screed a high standard of workmanship is essential.