When applied correctly, self levelling compound can transform an uneven subfloor into a smooth, professional-grade surface, ready for any type of floor covering. However, many DIYers and even experienced contractors make critical mistakes that can lead to unsatisfactory results, wasted time, and costly repairs. If you’re planning to use a self levelling compound for your next project, here are seven common mistakes to avoid and how to do it right.
1. Inadequate Subfloor Preparation
A smooth final result begins with a clean and properly prepared subfloor. Failing to do so is one of the most common reasons for a self-leveling compound job gone wrong.
Why it matters: Dirt, dust, oils, and debris prevent proper adhesion of the compound, leading to cracking, bubbling, or peeling.
How to avoid it:
- Thoroughly clean the subfloor using a vacuum and degreasing cleaner.
- Remove all loose materials and existing adhesive residues.
- Fill in any visible cracks or holes with a patching compound before pouring.
2. Skipping the Primer or Using the Wrong One
Primer is not optional. It plays a critical role in ensuring proper adhesion between the subfloor and the self-leveling compound.
Why it matters: Without a primer, the compound may absorb too quickly into the substrate, weakening its bond and leading to premature failure.
How to avoid it:
- Always use a manufacturer-recommended primer.
- Apply evenly and allow sufficient drying time as specified on the label.
- Don’t rush—some primers require multiple coats, especially on porous surfaces.
3. Incorrect Mixing Ratios
Precision matters when it comes to mixing self-leveling compounds.
Why it matters: Overwatering or undermixing can compromise the integrity of the compound, resulting in poor flow, lumps, or soft spots.
How to avoid it:
- Use clean, cold water and follow the manufacturer’s exact water-to-powder ratio.
- Mix with a drill and paddle mixer to ensure a smooth, lump-free consistency.
- Never add water after the initial mixing period.
4. Poor Pouring and Spreading Techniques
The way you pour and distribute the compound affects the final result more than you might think.
Why it matters: Uneven pouring and improper spreading can create air pockets, ridges, and inconsistent thickness.
How to avoid it:
- Pour the compound in a continuous motion to avoid cold joints.
- Use a gauge rake or smoother tool to help distribute it evenly.
- Work quickly and efficiently most compounds begin setting within 10-20 minutes.
5. Ignoring Temperature and Humidity Guidelines
Environmental conditions can make or break your leveling project.
Why it matters: Excessive humidity or extreme temperatures can alter curing times, affect consistency, and cause the compound to fail.
How to avoid it:
- Check the product label for optimal temperature and humidity ranges (typically 50°F to 70°F).
- Use fans, dehumidifiers, or heaters as needed to create a stable environment.
- Allow extra drying time if conditions are less than ideal.
6. Pouring Too Thick
It may be tempting to correct deep dips all at once, but over-pouring is a recipe for disaster.
Why it matters: Thicker layers can crack or settle unevenly during the curing process.
How to avoid it:
- Follow manufacturer guidelines on maximum pour thickness (often around 1/4 to 1 inch per layer).
- For deeper leveling, use multiple layers with proper curing time in between.
7. Not Allowing Enough Drying and Curing Time
Patience pays off rushing to install flooring can ruin all your hard work.
Why it matters: Walking on or installing flooring over a partially cured surface can cause indentations, bonding failure, or uneven flooring.
How to avoid it:
- Let the compound cure fully before walking on it (typically 4–24 hours, depending on the product).
- Wait the full recommended time before installing the final flooring layer.
- Test moisture levels if installing sensitive materials like hardwood or vinyl.
Final Thoughts: Set Yourself Up for Success
Self levelling compounds can be a powerful tool when used correctly. By avoiding these common mistakes and following manufacturer instructions to the letter, you can ensure a smooth, durable, and professional-looking finish that stands the test of time.
If you’re unsure or working with a complex subfloor, consider consulting a flooring professional for guidance.
Need help choosing the right self-levelling compound or tools for the job? Leave a comment below or contact us for personalized recommendations.
