A well-laid floor screed should provide a solid and level base for your flooring. However, if you’ve noticed that your floor screed feels spongy or soft underfoot, it could be a sign of underlying issues. A spongy screed not only affects the durability of your flooring but may also indicate a deeper problem that needs attention. In this blog post, we’ll explore the common causes of spongy floor screeds and what you can do to fix them.
Common Causes of a Spongy Floor Screed
Insufficient Curing Time
One of the main reasons floor screed feels soft is that it hasn’t had enough time to cure properly. Screed typically takes at least 24–48 hours to dry for light foot traffic and up to 28 days to fully cure, depending on the thickness and type used. If the screed is walked on too soon or has been covered before it has cured completely, it may remain weak and soft.
Incorrect Mix Ratio
The strength of floor screed depends on the correct mix of cement, sand, and water. If the mix is too wet or has too much sand and not enough cement, it will result in a weak screed that feels spongy. This is particularly common in DIY screeds or where the mix hasn’t been prepared correctly.
Poor Compaction
Screed needs to be compacted properly during installation to remove air pockets and ensure a solid, even surface. If the screed isn’t compacted properly, voids can form beneath the surface, leading to a spongy or bouncy feel.
Inadequate Substrate Preparation
Before laying screed, the substrate (the surface underneath) needs to be properly prepared. If there is dust, debris, or a lack of bonding between the substrate and the screed, the screed may not adhere correctly, leading to instability and a soft feel underfoot.
Use of an Incorrect Screed Type
Not all screeds are suitable for every application. Some lightweight or self-levelling screeds may not have the required strength for high-traffic areas. If the wrong type of screed has been used, it may not provide the necessary durability and could feel spongy over time.
Moisture Problems
Excess moisture beneath the screed can weaken its structure, making it feel soft or unstable. This is particularly common in areas with poor damp-proofing or where water ingress has occurred after screeding. Moisture can lead to delamination, where the screed separates from the substrate.
Issues with Underfloor Heating
If your screed has been laid over underfloor heating, an improper heating-up process may cause problems. Heating should be introduced gradually, following the manufacturer’s guidelines. If the screed has been heated too quickly, it can lead to expansion and contraction issues, making it feel unstable or spongy.
How to Fix a Spongy Floor Screed
Identify the Underlying Cause: Before making any repairs, it’s essential to determine why the screed feels spongy. Checking moisture levels, mix consistency, and bonding can help diagnose the issue.
Allow Proper Curing: If the screed is simply not fully cured, allowing it more time to dry and harden may resolve the issue. Avoid heavy foot traffic and covering it too soon.
Apply a Screed Hardener: For slightly soft screeds, applying a screed hardener can help reinforce the surface and improve durability.
Remove and Reapply Screed: In cases where the screed is severely spongy due to poor mixing, compaction, or incorrect application, removing the affected area and reapplying a properly mixed screed may be the best solution.
Improve Substrate Bonding: If poor adhesion to the substrate is the issue, reapplying the screed with a bonding agent can ensure a more stable and secure base.
Address Moisture Problems: If excess moisture is the cause, identifying and fixing the source of dampness—such as improving drainage or applying a damp-proof membrane—will help prevent further issues.
Preventing Spongy Screed in the Future
To avoid spongy screed problems in the future, follow these best practices:
Use the correct mix ratio for the screed type.
Ensure proper compaction during installation.
Allow adequate curing time before applying any flooring.
Properly prepare the substrate before screeding.
Follow the correct heating process if using underfloor heating.
Summary
A spongy floor screed is a clear sign that something isn’t right, whether it’s due to improper curing, poor mixing, or moisture issues. By identifying the cause and taking the right steps to fix it, you can ensure your flooring remains solid and durable for years to come. If you’re unsure about the condition of your screed, it’s always best to consult a professional to avoid costly repairs later.
Need expert advice on floor screeding? Get in touch today to ensure your screed is laid correctly the first time!
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