Screed flooring is used in countless commercial and industrial buildings worldwide (like schools, offices and warehouses) because of its versatility and its smooth, level surface finish. Screed flooring, however, can pose problems during installation, and failure to give the right care and attention can lead to issues like cracking and curling. But how do these issues occur, and how can these be prevented?
Wright Minimix are commercial concrete and screed flooring specialists with over 34 years’ experience supporting both trade and residential projects throughout the UK. As such, we believe we are best placed to explain to you all about screed cracking and curling, and how this can be prevented on your screed floor. Read on to learn more, along with how we can be trusted to design and install your screed floor.
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Why does my screed crack?
Typically common over larger areas, cracks can occur in awkward positions on your screed floor due to shrinkage as it dries naturally.
These cracks can also occur if there is too much water in the screed, as over-saturated screed can lead to excessive shrinkage and more cracking.
Why does my screed curl?
Curling or “lipping” of the screed happens when water moisture evaporates from the top part of the surface, meaning it will shrink and dry faster than the lower parts of the screed. This results in an upward curling of the screed.
Ways to prevent your screed from cracking or curling
We advise on considering the following to stop your screed from cracking or curling:
Mix the right proportions – BRE Drop Hammer Test
Mixing the right amount of cement and water in a screed mix is fundamental to preventing cracking or curling. Too little cement or water can mean your screed may not develop the required strength, whilst screed mixed with too much cement or water is more liable to cracking or curling.
We advise performing a BRE Drop Hammer test (whereby you drop a hammer down into the screed and measure the resulting indentation) to determine if your screed is strong enough to withstand weight bearing loads and foot traffic.
Add steel mesh for stress relief
Unbonded or floating screed are found to have a higher risk of curling and cracking at the joints. To reduce the risk, we recommend designing stress relief by adding and reinforcing steel mesh at the mid-depth of the screed.
Adequate screed thickness
We also advise deciding on the thickest screed possible for your project. This is because curling is more likely to be found in thinner unbonded screeds than thicker ones, as the thicker screeds have more strength to resist the curling forces.
Curing is a method of retaining the water in the screed for a period of time (normally seven days) to stop the screed from drying out too quickly and prevent excess evaporation of moisture from the surface.
This can be achieved by applying a polythene layer, but due to environmental and health and safety issues of using such material, the practice of curing is rarely used nowadays.
Sufficient drying time
You should allow the remaining water from your screed to escape before the installation of your moisture sensitive floor is complete. Although this could take a long time, it’s important to refrain from forced drying as this is a major cause of excessive drying shrinkage that in turn will cause cracking and curling.
Should you be working on a time sensitive project, we recommend a modified fast drying screed which is designed to dry in a more controlled, quicker manner whilst preventing curling or cracking. These screeds also provide the added benefit of doing away with the process of polythene curing.
Wright Minimix are experts specialist concrete and floor screeding
Wright Minimix are one of the UK’s leading suppliers of high quality liquid screed flooring, concrete blocks and ready mixed concrete. Our expert team of experienced concrete contractors have a wealth of knowledge and pride themselves on giving great practical advice across our commercial and residential clients.