What is the difference between concrete and screed – this is the question many people ask themselves who want to build a foundation, lay a terrace or simply inform themselves about building materials. Confusion often arises because concrete is used for foundations, but screed also comes to the floor.
There is also the term concrete screed. So what is the difference between the two terms or is it the same in the end? This guide is intended to help you
What is the difference between concrete and screed? In short: one is defined by ingredients, the other by the area of application.
What is concrete?
As already explained in the last guide to the question How long does concrete have to harden? concrete consists of granular stone such as gravel or sand, cement (which in turn consists of clay and lime), mixing water and, if necessary, other additives, binders or catalysts. In short, concrete is a moist mixture of rock, clay and lime.
When drying and curing concrete, there are chemical processes that lead to a crystalline bond.
This makes concrete hard and ideal for foundations and as a building material for other applications. There’s even concrete furniture! However, concrete is not the last layer for foundations, especially in the residential property sector, before laminate, tiles, parquet, linoleum, carpet, carpeting or the like can be applied to the floor. Because before the screed is needed…
What is screed?
Screed is the covering and straightening layer which is placed on the concrete foundation and levelled off. Screed can consist of similar components to concrete, but there are different types of screed. In other words: concrete is defined by its components; screed is defined by its function.
These types of screed exist:
- Cement screed (CT)
- Mastic asphalt screed (AS)
- Synthetic resin screed (SR)
- Calcium sulphate screed (CA)
- Magnesite screed (MA)
Not all types of screed use water, which is a big difference to concrete. This is because it requires water in order to become the resistant building material that many people appreciate and use.
The individual types of screed explained briefly
In the following, the five types of screed mentioned above will be examined in more detail. This gives you the opportunity to get a more precise picture of screed and make the difference to concrete.
Cement screed is a covering and straightening layer also called CT according to DIN EN 13 813. Cement screed is also called concrete screed, as the ingredients are approximately the same. Sand and cement are used, for example in a mixing ratio of 3:1.
The sand has a grain size of less than 8 mm, in some cases a maximum of 4 mm. Water is also used for mixing the mixture. Just like rapid concrete, there is also a rapid screed subtype for cement screed.
This has various additives which favour or accelerate the hardening process.
Mastic Asphalt Screed
Mastic asphalt screed is also called AS and, contrary to the above example, has nothing to do with water. This type of screed consists of the ingredients bitumen, sand, chippings and stone dust.
The mixture is heated to 230°C for pouring and spreading or for spreading mastic asphalt screed. The advantage of this screed is its resistance to water and steam.
The mixture also has a low thermal conductivity. Together with its impact sound insulating character, this type of screed often appears to be ideal for attics. Moreover, it is quickly ready.
However, there are also disadvantages: before wood, linoleum and other floor coverings are applied, a barrier layer must be created in order to avoid chemical interactions. Mastic asphalt screed should also not come into direct contact with mineral building materials.
Mortar water, for example, which has a highly alkaline character, is harmful to the mixture of substances. For masonry or other mortar applications, there must therefore be a separating layer between the mortar and mastic asphalt screed.
Synthetic Resin Screed
The synthetic resin used for synthetic resin screeds is usually epoxy resin. However, other plastics can also be used. Synthetic resin screed is not often used, which is partly due to its high price. Only if extremely short drying times are necessary or an increased dynamic load capacity is to be expected during subsequent use.
Although the advantage is that the screed is resistant to water, it is also discredited. Bisphenol A, one of the hardeners that can be used in synthetic resin screed, has fumes that make man infertile.
Calcium Sulphate Screed
Calcium sulphate screed is also colloquially called gypsum screed, because instead of cement as in concrete, calcium sulphate hemihydrate is used as binder. If this comes into contact with water, calcium sulphate dihydrate, i.e. gypsum, is formed.
The term anhydrite screed is also common. Sometimes calcium sulphate screed is preferred to cement screed, especially on larger surfaces. Because a lowering at the edges or the middle is to be expected here less. However, this screed is more susceptible to moisture, especially to permanent moisture with the risk of mould.
The last of the five screeds is the magnesite screed, which was formerly often called stone wood. Magnesite was mainly used for screeds after the Second World War, as cement was only sold / distributed rationed.
Therefore, the mixture of magnesia and magnesium chloride can be found in many corresponding old buildings. Instead of sand, wood was used as chips or flour. This is also the reason for the biggest disadvantage of this screed: a high susceptibility to moisture and wetness. For the garden and the terrace it is absolutely nothing!
What does the term useful screed mean?
Useful screed refers to screeds that are used directly as flooring without the application of floor covering. Especially in industry and halls (warehouses, trade fairs, machine halls), no further floor covering is applied to the concrete or cement screed.
To make this type of substrate durable for a long time and to reduce maintenance to a minimum, you can use concrete sealing as a successful method, among other things. In addition to the corresponding screeds, our products and processes can also be used directly for concrete. If you have any questions, please contact us or one of our user partners.
Difference between concrete and screed – Summary
If you were simply looking for an answer to the question“What is the difference between concrete and screed? We hope that we have been able to help you in your search for answers on the subject of construction, house and garden.
Further details, DIN codes, procedures, advantages and disadvantages of the individual screeds can also be found on Wikipedia and the sources listed there. This encyclopedia entry helped this article. If you have further questions on the subject of concrete and are looking for answers, visit us from time to time – this guidebook area is constantly being expanded!
We hope that now all questions are answered and that you have all necessary information for the construction of the desired underground. If you are looking for further information on concrete, building, sealing and similar topics, please have a look at our other articles.