How Long Does Screed Take to Dry Before Tiling?

When planning a tiling project, one of the most important questions to ask is, how long does screed take to dry before tiling? The drying time of cement screed can make or break your flooring installation. Laying tiles on a screed that hasn’t dried fully can lead to serious problems such as lifting, cracking, and moisture-related damage, meaning you'll have to redo the lot! This is why understanding the screed drying process is a vital part of successful floor preparation, lets find out more about drying times and things to look out for before tiling.

​What is a Floor Screed?

A floor screed is a thin, top-layer material applied over a concrete subfloor to provide a level base for finishing materials such as tiles, wood flooring, or carpet. It creates a smooth finish that ensures a stable and even surface for the installation of flooring. The quality of the screed surface is fundamental to the long-term performance of the finished floor, if your screed fails your expensive new flooring will too. Depending on the project requirements, different types of screed may be used. These include traditional cement-based screeds and modern liquid screeds such as anhydrite screeds. The choice of material and application method directly influences how long the screed takes to dry, which in turn affects the overall project timeline.

​Types of Screed and Their Impact on Drying Time

The type of screed plays a major role in determining how long the screed drying period will be. Traditional cement-based screeds are known for their strength and versatility but generally require longer drying times. On average, a cement-based screed dries at a rate of about 1mm per day for the first 40mm of thickness, under ideal conditions.

On the other hand, liquid screed, often made from calcium sulphate, is self-leveling and allows for faster application and smoother finishes. These screeds are popular for large surface areas and projects on tighter schedules. In some cases, liquid screeds can be completely dry and ready for tiling in as little as 20 days, provided that proper drying conditions are maintained.
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In addition, screeds may be categorised based on how they interact with the substrate. Bonded screeds are applied directly onto the base, while un-bonded and floating screeds are laid over a separating membrane or insulation layer, respectively. Projects that incorporate underfloor heating often use floating screeds, which adds complexity to the drying out process.

​Factors That Greatly Affect Screed Drying Time

At Concrete In Cornwall, we understand that the screed drying time is greatly affected by environmental and situational conditions. Key among these are ambient humidity, temperature, and ventilation. High humidity levels slow down moisture evaporation, keeping the screed damp for longer. In contrast, warm temperatures and dry air can help accelerate the drying phase.

Good ventilation plays a critical role in speeding up the screed drying. We often recommend opening windows to allow moisture to evaporate naturally, especially after the initial 48-hour curing period, when the screed should not be disturbed. Without proper airflow, trapped moisture may remain within the screed surface, prolonging the overall drying time.
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The thickness of the screed also determines how long it takes to dry. Thicker layers retain more moisture, which takes longer to evaporate. At Concrete In Cornwall, we advise that additives can be used to modify drying characteristics, but they must be used correctly, according to manufacturer instructions, to avoid weakening the floor screed.

​The Screed Drying Process in Detail

The process of drying begins with an initial curing stage, typically lasting 24 to 48 hours. During this phase, the screed should not be walked on or exposed to mechanical stress. This early stage allows the material to harden and form its structure.

Following the initial cure, the screed floor enters the main drying out process, where moisture evaporates gradually from the material. For cement-based screeds, this may take around 28 days, though the exact screed drying time depends on both internal and external conditions.
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When underfloor heating is present, it can be activated to speed up the drying. However, the heating system must be commissioned carefully, typically starting at a low temperature after seven days and then increasing gradually over a 7–10 day period. Abrupt temperature changes can damage the screed surface and lead to cracks or weak spots.

​Moisture Testing Before Laying Tiles

Regardless of the time elapsed, moisture testing is essential before proceeding with laying tiles. Even if a screed floor appears dry, it may still contain residual moisture that can compromise adhesion or cause damage to the finished flooring.

Several methods can be used to assess moisture content. Surface moisture meters provide a quick check, though they may not always reflect deeper moisture. More accurate results come from hygrometer testing or core sampling, which measure internal levels and give a clearer picture of whether the screed is completely dry.
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The target moisture content will depend on the type of screed used. For cement-based screeds, the safe threshold is generally around 0.5% CM, while anhydrite screeds require lower levels, typically around 0.3% CM.

​Risks of Tiling Too Early - Don't do it!

Laying tiles on a screed that hasn't dried properly can have costly consequences. The adhesive may fail to bond, or the tiles could become uneven due to shifting or shrinking of the screed. In worst-case scenarios, weak spots or cracks may develop in the screed surface, undermining the entire flooring structure.
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Moisture trapped under tiles can also lead to the development of mold or mildew, especially in bathrooms and kitchens. These issues can be expensive to fix and may require the floor to be removed and relaid entirely. That’s why allowing adequate screed drying time is not just a recommendation—it’s a necessity.

​Estimating Screed Drying Times for Your Project

Creating a realistic estimate for how long your screed to dry will take is crucial for planning. As a general rule, plan for about 1mm per day up to 40mm in thickness for cement-based screeds. For liquid screeds, you might expect quicker drying, but only under controlled conditions with proper ventilation and temperature regulation.
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If you're working with underfloor heating, add time for the commissioning process and consider a heat-cool cycle before laying tiles. Always follow the manufacturer’s guidelines for both the screed and the tile adhesive to ensure compatibility and optimal performance.

Conclusion

In summary, if you're wondering how long does cement screed take to dry before tiling, the answer depends on the type of screed, environmental conditions, and project specifications. While 28 days is a good average benchmark for cement-based screeds, anhydrite screeds or liquid screeds may dry faster. No matter what, always test for moisture content before proceeding with tiling. Rushing this step can lead to significant structural issues and costly repairs. By understanding the screed drying out process in depth, you'll be better equipped to make informed decisions and achieve a durable, professional result in your next flooring project.