An uneven cured surface is usually caused by inconsistent mixing between batches, working the material with a rake or trowel after it began to set, an underlying subfloor that wasn't checked for level first, or pouring too small a batch to cover a large area within the working time.
How to Check If It's Actually Not Level
Use a long straightedge or laser level across the room in multiple directions. A small amount of variation is normal and often within the flooring manufacturer's tolerance; document the high and low points before deciding whether the floor needs correction.
Common Causes
- Inconsistent batch mixing: Slightly different water ratios between batches change flow and final height.
- Working the material too long: Self-leveler needs to flow on its own — over-raking after it starts to set can leave rake marks and ridges.
- Subfloor wasn't checked first: A self-leveler corrects moderate unevenness, but severe structural dips may need a preliminary patch or additional lifts.
- Pour interrupted or too slow: If a batch starts to set before the next is poured, a visible seam or step can form between sections.
Fixing High Spots
Small high spots can often be sanded or ground down once the pour is fully cured, using a floor grinder with dust control. Confirm the flooring manufacturer's flatness tolerance before grinding, since some tolerance is normal and expected.
Fixing Low Spots
Low spots are usually corrected with an additional thin lift of self-leveling compound once the base layer has cured enough to accept another pour, following the manufacturer's re-coat guidance and priming between lifts if required.
Preventing It Next Time
Measure and pre-mark the room's low and high points before pouring, prepare all batches to the same measured water ratio, and pour continuously across a room rather than working long sections between batches. For larger rooms, consider working with a second person so mixing and pouring can happen in parallel.
Frequently Asked Questions
Is a small amount of unevenness after pouring normal?
Yes — most flooring manufacturers specify an acceptable flatness tolerance (often within 1/8–3/16 in over a set distance), so minor variation is expected and not necessarily a failed pour.
Can I just add more self-leveler on top to fix low spots?
Usually yes, once the existing layer has cured to the point the manufacturer allows another lift, and after any required priming between layers.
Related Guides
Sources & References
- Flooring manufacturer flatness tolerance specifications
- Self-leveling compound manufacturer re-coat and lift guidance