What is screed?
Screed is a thin layer of material that is poured or laid over a concrete base to create a smooth and level surface. It can be left bare e.g. for warehouse or industrial flooring where scuff marks are to be expected, but is more commonly covered with a decorative final floor such as carpet, tiling, laminate, vinyl, stone or wood.
What is screed used for?
Screed is designed to provide a sturdy, smooth and even surface. Once a concrete subfloor has been laid, screed is typically used to provide a flat layer for other types of flooring to be laid directly onto, but it can also help to even out a floor, ensuring it is clean, safe and level.
Screed is extremely durable and able to withstand heavy footfall and constant usage, meaning floors are protected and should last longer. It is available in a range of strength grades depending on the application. Screed is also highly insulating and is therefore often used on top of damp proof membranes or underfloor heating systems.
What is it used for?
Screed consists of a combination of cement, sand and water, with the ratio of sand varying to suit the application. For instance, a sharp sand is used to make fine screed whereas for more industrial, heavy-duty requirements, a coarse aggregate is added to create a thicker layer. Screed’s consistency is similar to concrete but is much smoother, making it an ideal finishing layer.
The different types of screed
You’ll find there are three main types of screed. These are:
Cementitious flowing floor screed, such as Cemfloor, is delivered in truck mixers and placed in-situ by pumping. Easy to install and self-compacting, cementitious flowing screed is designed for use over thermal or acoustic installation as it improves efficiency by eliminating drafts, preventing pipes from freezing and creating a moisture barrier.
Free flowing floor screeds made with a high quality Gyspol anhydrite, specially graded sands and selected additives are placed by pump or chute and allow for rapid installation, strength gain and setting, significantly reducing construction programme times. Self-compacting and high performance, flowing anhydrite screed, such as Highflow Rapide, is also self-curing and requires no membrane after installation, making it ideal for all construction types including traditional masonry, lightweight steel frame, timber frame and high strength.
Semi-dry screeds, such as Screedform, are cement-based and produced under factory conditions to achieve a range of strength grades and enable reduced drying times. Suitable for placement as a subfloor above and below DPC level, semi-dry screeds can be used for bonded, unbonded or monolithic applications including residential, commercial and public buildings. Semi-dry screeds are ideal for areas prone to wet conditions such as bathrooms, en-suites, changing rooms and swimming pool surrounds.
What is the difference between screed and concrete?
While screed and concrete are both made from a cement, sand and water mix, their differences lie in their composition and function. Concrete is designed for strength and is therefore denser and courser. Screed is used as a finishing layer so has a thinner, smoother consistency.
Why use screed instead of concrete?
Screed offers versatility; you can leave as is for an industrial appearance, or top with other flooring finishes to suit the space. It can also have both self-levelling and insulating properties, and can extend the lifespan of your floor. Available in semi-dry or flowing screed, it is typically for use in thin sections when compared to concrete.
It’s important to distinguish where screed can bring real benefit to your project. With a variety of applications from domestic properties to city construction, screed can achieve optimum end results.