An essential guide to screed
Concrete is the world’s most widely used construction material, second only to water. Dating
back to Roman times (The Pantheon in Rome is the world’s largest unreinforced concrete
dome), it is an essential ingredient of global landmarks, buildings and infrastructure. As one
of the UK’s leading producers of ready-mixed concrete products, our experts have prepared
this guide to share their knowledge of concrete including its uses, composition, costs and
sustainability credentials…
Summary of key points:
- Screed is a thin layer of material used to create a smooth and level surface on top of a concrete base
- Screed is commonly used as a base for other types of flooring
- Screed is made of a combination of cement, sand, and water, and is available in different strength grades
- There are three main types of screed: flowing (cementitious), flowing (anhydrite), and semi-dry
- Screed is different from concrete in its composition and function, with screed being smoother and used as a finishing layer, while concrete is denser and designed for strength
- Screed can be a versatile option, with the ability to leave it bare for an industrial look, or add other flooring finishes, and can also have self-leveling and insulating properties, extending the lifespan of the floor.
Read more about our branded concrete mixes which are accredited BES 60001
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:
Flowing (Cementitious)
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.
Flowing (Anhydrite)
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
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.
Conclusion
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.
Frequently Asked Questions
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.
Floating screed is one the three main types of screed and is generally laid on a layer of
insulation, unbonded from the concrete base. Floating screed is used for acoustic or thermal
insulation, or in buildings with underfloor heating.
Latex screed is a self-levelling compound that includes resin. This ensures a smooth,
consistent and level finish on any surface, so is ideal for patching up a bad job! Latex screed
is rapid drying and can be applied to small or large areas. Latex screed does not contain
protein, meaning it is excellent for high safety/hygiene locations such as hospitals, surgeries
and medical centres.
Liquid, or flow, screed is a fast drying, easy-to-apply screed that is suitable for almost all
building projects. Self-levelling and self-compacting, liquid screeds are pumped into place,
allowing for a much thinner coating to match any depth.
