For those not working in the construction industry and to the untrained eye, it may be difficult to both understand and / or recognise the difference between concrete and floor screeds.
Something that is very odd given that both materials are made from the same basic ingredients; cement, aggregates and water.
The basic chemistry is the same for both concrete and screed – the cement and water forms a paste and coats the surface of the sand or the aggregates, and the cement paste hardens by a process called hydration, forming a hardened mass of high strength and durability.
However, the size of aggregates used is different, the grade of the cement used is different, the mix consistency and finish is different – because both materials intended use is very different!
Concrete has a much coarser mixture than screed, consisting of larger, hard-core aggregates, which are the key element that gives it its durability and makes it strong and long lasting.
Applying a semi-dry cementitious type of screed
Because concrete has the potential to hit very high strengths, it is used across the construction industry for structural purposes – including floor slabs. It is the most used man-made material in the world.
Screed however is a smoother mix, which consists of considerably less aggregates to that of the mix used for concrete.
Screed is usually applied on top of the concrete slab and is most commonly used as a finishing layer on internal floors or to level the floor prior to final floor coverings carpet, tiles, natural stone, linoleum, wood flooring, resin coatings etc.
Screeds are required when a colourful or functional floor is needed rather than a bare concrete surface. For industrial purposes, or commercial locations, which will undergo frequent traffic, a more robust screed is required than is used in DIY or residential projects.
Most screeds are used for internal purposes only, often covering heating systems, acoustic or thermal insulation. Polymer-modified screeds can be installed in external locations, as they are hardwearing, water resistant and able to withstand a more rigorous environment.
Screed covering a heating system
Traditionally screeds are sand and cement mixtures, blended and applied on site. However these are often unpredictable as the ratios and properties cannot be exactly determined and so can lead to a weak flooring layer liable to crack, peel or collapse without warning.
To counter this unreliability there are a number of proprietary screeds and kits available on the market offering enhanced strength and a faster application speed that will react more predictably.
12 thoughts on “Concrete vs Floor Screeds: What is The Difference?”
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So how do one screed on plain concrete
Hi, thanks for your comment. The application method will differ depending on the type of screed being installed. This blog post looks at how to apply semi-dry cementitious type screeds (https://bit.ly/2Af6rul).
Cheers,
Dan
Hi,
Is screed suitable for a final finish in a home? It has been suggested to me that a typical screed is not as hard wearing as concrete and therefore more suitable to covering with engineered flooring, tiles, etc. Our architect has specified “concrete screed” as the final floor finish and I’m not sure he knows himself whether it’s screed or concrete.
Can you help shed light on the subject.
Thanks
Hi Andrew
The term screed is often confusingly used to refer to both a finish and an underlayment and this is true for cementitious (or concrete) screeds as well. This is an example of a cementitious screed finish (http://bit.ly/2QWGZNk) and this post is on cementitious screeds as an underlying layer to bond the final coating to the substrate (http://bit.ly/2RQGdGo). I would say that it’s not impossible to use it as a finish in a home, however we more commonly see people go for a polished concrete type finish if this is the type of look/feel you’re after. This post goes into a bit more detail on polished concrete (http://bit.ly/2Rz2xFb). Unfortunately given the large number of different screeds and concrete out there and the cross overs between the two, we’d advise talking to the product manufacturer before applying it to make sure that it’ll be right for the task at hand. Hope that helps a bit.
Kind regards,
Dan
It got me when you said that concrete is more durable which is why it will last longer. I will definitely pick this for the flooring of our home as well as the other parts to give me peace of mind. As of now, we are still waiting to be approved to the loan that we are applying for, so we can have our dream home custom-built. Thanks for the information anyway!
I like how you mentioned that getting concrete flooring is a good idea since it lasts longer–even more so if there’s a top layer of screed applied atop it. At the same time, there’s also the choice of either leaving the floor as it is or using screed to make the floor much more colorful–while at the same time maintaining functionality. If I had the chance to get concrete flooring then I would do it since I’m looking for something durable that can last a long time.
Hi, i have applied screed and less than a week later it has cracks which sound hollow when tamping, i had planned to acid stain it, what do i do to fix the cracks?
Hi Jaqueline
The cracking sounds like it could be shrinkage cracking, which tends to happen if the applied screed hasn’t cured properly. Crack repair materials are available, such as PHS (http://bit.ly/2JrZrxh), which can be used for both crack repairs and stitch pinning to rebond a screed that is not fully bonded to the underlying base. However the repair will be visible, this isn’t a problem if the screed is simply being used to level the floor prior to applying a finish, but if you’re intending to stain the screed and leave it exposed then this could be a consideration.
Kind regards,
Dan
I also encountered cracks on screeds. For future applications, can you give suggestions on how to prevent cracks? Thank you.
Hi Philip
Thanks for your question. As it happens, we’ve got a white paper that looks into screed application and how to avoid problems like cracks. Click here to read the white paper – http://bit.ly/2IapyaQ
Cheers,
Dan
Hi,
I am getting an extention done and I was wondering if there is a need to screed once the foundations and concrete floor is complete. The area will be a dining area where i will be putting down a laminate floor. Will there be a need for screed to be done if the concrete floor is level?
Many thanks.
Hi Paul
Thanks for your question.
If the concrete is of a high quality and you do not require a screed to level out the substrate, add strength or cover insulation/underfloor heating and if the laminate will bond to the concrete then it is likely that you don’t need a screed in this instance.
Kind regards,
Dan