What Is Screed and How Is It Different From Concrete?

screed versus concrete

In construction, there are two different types of materials used to create finished forms and floors: screed and concrete. While the process for mixing and handling these materials may be similar, both have different applications and use cases.

Here is some basic information about screed, how it’s different from concrete, and when it’s best to use it.

How Is Screed Different Than Concrete?

Screed and concrete are very similar in their ingredient makeup. Although both finished products are made from aggregate, cement, and water, what makes them different is the size of the aggregate used in the mix, along with the cement grade and consistency.

Screed is a much smoother mix that contains fewer aggregates than concrete and is most typically used as a top layer for finished floors. Concrete contains a more abrasive mixture of aggregates and cement and is mostly used for structural jobs where strength is the primary importance.

How is Screed Applied in Construction?

There are several ways screed can be applied after it has been mixed. In many cases, the screed is directly bonded to a finished concrete slab to provide a smooth finish. However, screed can also be placed unbonded to a surface using a damp proof membrane or over certain types of insulation. In some cases, reinforcements are laid in the form of glass mesh or polypropylene to create a robust and secure bond.

Screed mixtures can be prepared ahead of time at a mixing factory or managed on site. Screed can vary widely in composition depending on the application its being used in and how quickly it needs to set up. When using screed with underfloor heating systems, a different thickness of the screed will need to be put in place before allowing it to set fully.

What Are the Types of Screed?

When applying screed in construction projects, three main types are used: bonded, unbonded, and floating.

Bonded

Bonded screed is attached directly to the concrete substrate through the use of a bonding slurry. This type of screed is used in thinner applications where there is more dependence on the structural integrity of the concrete.

Unbonded

Unbonded screed is not bonded directly to the concrete but instead is molded to a moisture-proof membrane on top of the concrete. These types of screed are often referred to as “structural toppings” and are typically 40mm – 75mm in thickness.

Floating (With or Without Underfloor Heating)

Floating screed has become a popular solution for homes with heated and insulated flooring. Floating screed has an additional layer of thermal insulation and heating elements between the base of the concrete and the screed and rests unbonded from the substrate. This type of screed is the thickest of all three categories and is usually 65mm – 75mm+ in depth.

Laying screed under concrete in Columbia, SC is an essential step to providing smooth and even surfaces to uneven or potentially unsafe sub-bases. It can be used in both commercial and residential projects and is suitable for all types of flooring.

Family owned and operated since 1969, Knight’s Companies is a concrete company in Columbia, SC. Knight’s upholds the highest standards in all aspects of the business, and will complete commercial concrete jobs other companies won’t even quote.