Cementitious levelling screeds
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.
The benefits of factory-produced screeds include:
- Accurate cement content
- Consistent cement strength class
- Consistent finished product strength
- Reduced on site labour costs
- Reduced wastage and pilferage
- Guaranteed end performance Technical advice and test date available upon request
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:
- Scale of application, up to 2000 m2 per day
- Provide a finer surface finish
- Can be installed to precise level
- Have reduced section thickness due to greater flexural strength
- Have significantly less movement joints due to its minimal drying shrinkage
- Improved thermal efficiency when used with underfloor heating systems
- Self compacting
- Reduced curing
- Can be force dried, reducing programme times
For further information
For further information on screed availability and technical details contact an MIA member by clicking here.