Ensuring Screed Compatibility with Adhesives and Floor Materials

It is essential to ensure that the screed chosen for any project is suitable for and compatible with the floor finish that is going to be applied on top of it. All screeds can be used with most floor finishes but that is not to say that all screeds are ideal. Not every screed is the same, and some will make the application of the floor covering more difficult and potentially with a higher risk of failure.

Any liquid screed should provide a good standard of levelness and surface regularity, and so will provide a good base for floor finishes.

Cement-based liquid screeds, such as Cemfloor, offer further advantages in that they simplify the installation process and remove any potential risks of incompatibility with the cement based adhesives and levellers that will be used on top of them.

The very reliable and speedy drying of cement based materials also removes an area of concern or potential delay.

In this blog, we will explore the advantages of cement-based liquid screeds, and the best practices for ensuring a high standard and risk free installation. Let’s discover how cement-based liquid screeds can enhance the performance of your floor installations, setting the stage for successful projects and satisfied clients.

Compatibility with Cement-Based Adhesives

When it comes to choosing a screed for your floor installation project, compatibility with adhesives is a critical consideration. Tile adhesives, vinyl adhesives, levellers and, in fact, almost anything that we want to apply to a screed are, in almost all cases, cement based.

Cement materials do not behave well when in contact with gypsum, which other types of flow screed contain. Whilst contact between the two types of material can be prevented by suitable and correctly applied priming there is always some risk that a reaction will take place at the interface that will both destroy the adhesion and, much worse, expand to push the floor finish from the screed.

Cement-based liquid screeds remove this risk completely since they contain no gypsum and, perhaps to state the obvious, cement is compatible with cement.

Installing Screed: When To Apply The Covering & Adhesives

In addition to their compatibility with cement-based adhesives, cement-based liquid screeds offer the advantage of fast and predictable drying properties and, in the event of an extremely fast programme, the possibility to force dry.

This allows for a more efficient installation process, reducing project timelines and minimising delays.

Force drying is done by applying controlled heat and airflow to the screed to cause more rapid movement of moisture from the screed and so a shorter overall drying time. This enables installers to proceed with subsequent steps, such as applying floor coverings, in a shorter time frame.

It must be said though that, with the already fast and reliable drying times of cement based screeds such as Cemfloor, this process is rarely necessary. It’s good to know that it’s possible though when time is short.

Under normal circumstances, cement-based liquid screeds require the screeded area to be sealed for 24 to 48 hours when the installation is complete. After this the room’s doors and windows should be opened to allow ventilation to assist in the drying process and the screed will be ready for foot traffic.

After 7 days full site traffic can be resumed and commissioning of underfloor heating or force drying can be commenced if needed.

Moisture Content

Before moisture sensitive floor finishes such as, for example, vinyl or timber are installed, the moisture content of the screed should be checked to ensure that it is adequately dry.

Usually, the required moisture content can be obtained from the appropriate British Standard or from the manufacturer of the floor finish.

Typically the moisture content would need to be a maximum of 2.5% (by weight) for a cement based screed such as Cemfloor but would need to be as low as 0.5% for an anhydrite / gypsum based screed.

There are a several test methods that can be used to ascertain the moisture content of a screed and there is much debate on which are suitable and which is the best.

Of all the methods however, only one is currently recognised by British Standards and, until this changes, we are required to ascertain the relative humidity of a pocket still of air trapped in contact with the screed.

For many floor finishes this must be no higher than 75% which does correlate approximately with the “by weight” % figures as above.

Preparing The Surface: No More Grinding

Unlike most calcium sulphate based/gypsum screeds, cement-based alternatives do not produce a laitance layer at their surface during installation. This results in a surface that does not need to be sanded down or ground for this layer to be removed.

There is no doubt that failure to remove laitance has resulted in many problems with floor finishes.

There has always been a temptation to just ignore the fact that the sanding should be done, saving a costly and hoping that it will be OK.

Unfortunately it won’t be OK, not sanding the laitance will cause debonding. Cement based materials sidestep this risk entirely by the simple fact that there is no laitance to remove and so no cost to do so.

It should be pointed out that the process of removing the laitance is not the same as the process of preparing a floor screed for the final floor finish. This final preparation will be necessary for any screed including a cement based screed or a gypsum screed from which the laitance has already been removed. The degree of preparation needed will depend on the exact finish to be applied but will vary from nothing at all to a light abrasion.

It’s important to note that some coverings may come with bespoke manufacturer guidelines which require the screed to be worked further in order to be mechanically prepared for the surface material. This will be required, no matter which screed type is used.

Conclusion

The compatibility of cement-based liquid screeds with adhesives and other overlayments, their reliable and quick drying properties and their ability to be force dried make them an excellent choice for efficient and successful floor installations and savings in programme time.

Cemfloor Approved Installer Program

That's why we created the Cemfloor Approved Installer Program, aimed at assisting screed installers in consistently delivering success and quality to their customers through Cemfloor products. 

Tailored to your needs, this 1-hour training course focuses on essential guidelines for installing Cemfloor's cement-based liquid screeds and meeting manufacturer standards time and time again.

Cemfloor has built a strong reputation as a trusted manufacturer and provider of screeds, specialising in high-quality cement-based liquid screeds for projects ranging from domestic to commercial sites.

With Cemfloor products and our unwavering commitment to quality, installers can confidently install floors, knowing that the product is always of the highest standard, carrying both UKCA and CE marks. 

Join the Cemfloor Screed Installer Program today and become part of a growing community of skilled professionals dedicated to delivering quality-driven projects to their clients.