anhydrite screed cracking causes, prevention, repair, and maintenance tips

What Do You Need to Know About Anhydrite Screed Cracking?

Anhydrite Screed Cracking refers to the formation of fractures or splits within anhydrite screed, a type of flooring solution made from a gypsum-based compound. These cracks can vary in size and severity, from minor hairline fractures to more substantial splits that compromise the integrity of the flooring. 

Anhydrite screed is prized for its quick installation time, smooth finish, and efficient thermal conductivity, making it a popular choice for underfloor heating systems. However, improper installation, environmental factors, or material inconsistencies can lead to cracking, which undermines the durability and aesthetic appeal of the floor. Addressing these cracks promptly is essential to maintain the functionality and longevity of the screed.

What is Anhydrite Screed and Why is It Used?

Anhydrite Screed, known for its quick drying time and easy application, is a popular choice for flooring in both residential and commercial projects. This type of screed, made from a calcium sulfate binder, offers several advantages, including a smooth finish and excellent thermal conductivity, making it ideal for use with underfloor heating systems.

However, like any other material, it is not immune to issues, with cracking being one of the most common problems that can arise during or after the installation process. Understanding the causes, such as shrinkage, thermal movement, or improper mixing, as well as implementing effective prevention methods like controlling environmental conditions and ensuring proper installation techniques, is crucial.

Additionally, knowing various repair techniques for anhydrite screed cracking is essential for maintaining a durable and long-lasting floor. Regular maintenance and early intervention can help mitigate these issues, ensuring the flooring system remains functional and aesthetically pleasing for years to come.

What Causes Anhydrite Screed to Crack?

Anhydrite screed cracking can occur due to several reasons, each contributing to the weakening of the flooring. Understanding these causes can help in prevention and ensuring a long-lasting, durable surface.

Cause Description
Insufficient Drying Time Covering the screed before it has adequately dried, leading to shrinkage and cracking.
Rapid Environmental Changes Sudden shifts in temperature or humidity during installation or drying can cause the screed to expand or contract too quickly.
Overloading Placing heavy loads on the screed before it has fully dried or hardened can create stress fractures.
Poor Installation Practices Inadequate compaction or uneven thickness can lead to weak spots that crack under pressure.
Incompatible Water Ratio Using too much or too little water in the mix can cause improper curing and shrinkage, leading to cracks.

Insufficient Drying Time

One common cause is insufficient drying time. Anhydrite screed requires a specific period to dry and cure properly. If the screed is covered before it has adequately dried, this can lead to shrinkage and subsequent cracking. The recommended drying time must be adhered to, taking into account factors such as thickness and environmental conditions.

Rapid Environmental Changes

Sudden shifts in temperature or humidity during installation or drying phases can cause the screed to expand or contract too quickly, leading to cracks. For instance, exposure to direct sunlight or rapid cooling can induce stress within the material. Employing measures to control the environment during installation can mitigate the risks of rapid environmental changes.


Overloading the screed before it is fully dried or hardened can also create stress fractures, compromising the surface. This is particularly critical in high-traffic areas or where heavy equipment is placed. Ensuring the screed has reached its full strength before subjecting it to loads is essential for maintaining its integrity.

Poor Installation Practices

Poor installation practices further contribute to anhydrite screed cracking. Inadequate compaction or uneven thickness during the installation process can create weak spots that are prone to cracking under pressure. Additionally, failing to follow manufacturer guidelines and recommended installation techniques can exacerbate these issues.

Incompatible Water Ratio

Finally, an incompatible water ratio during mixing can severely affect the screed’s integrity. Using too much or too little water can cause improper curing and shrinkage, leading to the formation of cracks. Maintaining the correct water-to-screed ratio is crucial for achieving the desired consistency and strength. It is advisable to follow precise measurements and mixing instructions to ensure optimal results.

Prevention of anhydrite screed cracking relies heavily on careful planning, adherence to guidelines, and control over environmental and procedural variables. By paying attention to these details, one can ensure a smooth, durable, and long-lasting flooring solution. 

How Do I Prevent Screed From Cracking?

To prevent cracking in anhydrite screed, it’s essential to follow best practices during preparation, installation, and curing. Here are some practical tips:

  • Ensure Thorough Drying: Allow sufficient time for the screed to dry completely before applying any covering or subjecting it to load. This can sometimes take several weeks depending on the thickness and environmental conditions, so it’s crucial to be patient.
  • Maintain Stable Conditions: Keep environmental conditions stable during installation and drying, avoiding rapid changes in temperature and humidity. Large fluctuations can cause the screed to expand or contract too quickly, leading to cracks.
  • Avoid Premature Loading: Do not overload the screed until it has reached the recommended strength and moisture content. Premature loading can compromise the structural integrity of the screed and lead to long-term issues.
  • Adhere to Best Practices: Follow proper installation methods, including adequate compaction and ensuring an even thickness throughout. Uneven application can cause weak points that are susceptible to cracking under pressure.
  • Correct Water-to-Screed Ratio: Use the appropriate amount of water during mixing to avoid shrinkage and ensure proper curing. Too much water can make the mixture too fluid, leading to potential shrinkage, while too little can make it too stiff, affecting the curing process.
  • Regular Monitoring and Maintenance: Regularly check the screed for any signs of cracking or damage, and conduct maintenance as needed. Early detection can prevent minor issues from becoming major problems.

What are the Methods of Preventing Anhydrite Screed Cracking?

When cracks do appear in your anhydrite screed, addressing them promptly and effectively is key to preventing further damage. Here are the methods to repair anhydrite screed cracking:

Crack Type Repair Method
Hairline Cracks Apply a suitable filler or jointing compound to seal the cracks.
Larger Cracks Use a two-step process: fill the crack with a repair mortar, then apply a compatible sealant to prevent future cracking.
Significant Damage In cases of extensive damage, partial or complete replacement of the affected screed may be necessary.
Underlying Issues Identify and address the root cause of cracking to prevent recurrence.
Professional Assistance Seek expert advice to ensure effective and lasting repairs.

What Are Some Real World Examples and Case Studies for Anhydrite Screed Cracking?

screed cracking causes, prevention, repair, and maintenance tips

Apart from the theoretical causes and prevention techniques of anhydrite screed cracking. There must be some clear understanding of anhydrite screed cracking through some practical examples. Let us guide you through the whole process with some simple case studies: 

Case Study 1: Residential Building

Location: Residential building in a temperate climate.

Issue: Anhydrite screed cracking was observed after only a few months of installation.

Cause: Rapid change in environmental conditions from warm and humid to cold and dry.

Solution: Repair involved filling the cracks with a compatible repair mortar and sealing with a suitable sealant, followed by adjusting environmental controls to ensure stable conditions for proper drying.

Case Study 2: Commercial Space

Location: Commercial space with heavy foot traffic, including retail areas and corridors.

Issue: Anhydrite screed cracking and damage within a year of installation.

Cause: Overloading and high point loads on the screed before it had fully dried and reached the required strength.

Solution: Partial replacement of the damaged areas with a focus on proper compaction during installation and stricter control of access until the screed had fully dried and hardened.

Case Study 3: Industrial Facility

Location: Industrial facility with anhydrite screed used in production areas.

Issue: Extensive cracking observed across the production floor, affecting operations.

Cause: Inadequate compaction and uneven thickness during installation, leading to differential drying and shrinkage.

Solution: Complete replacement of the anhydrite screed with improved installation practices, including more careful compaction and ensuring even thickness.

Why Call a Professional for Anhydrite Screed Cracking Solutions?

Hiring a professional for anhydrite screed cracking solutions is crucial, and experts like The London Screed Company have the knowledge and tools for the job. Here’s why:

Experience and Expertise

Professionals have years of experience and know the best ways to fix cracks, ensuring long-lasting repairs.

Proper Tools and Materials

They use advanced tools and high-quality materials for quick and effective repairs, preventing future issues.

Saves Time and Effort

Professionals complete the job faster and with less hassle, freeing you to focus on other tasks.

Prevents Further Damage

Experts avoid mistakes that could worsen your floor’s condition, ensuring the problem is fully resolved.

Quality Assurance

The London Screed Company offers a quality guarantee, ensuring the job is done right and any issues are fixed without extra cost.


Professionals handle hazardous materials and heavy equipment safely, reducing the risk of accidents.

In summary, calling The London Screed Company for your anhydrite screed cracking solutions brings experience, the right tools, and a quality commitment, ensuring your floor is in the best hands.