What this work covers
Self-levelling compound is an underlayment, not the finished floor. It flows across shallow irregularities before vinyl or SPC is installed. The word self-levelling can be misleading: weak dust, skipped primer, excess water, trapped air, or rushed curing can leave a surface that looks flat but cracks or powders under the final flooring.
When this work is needed
Use it where shallow waves or small level changes would telegraph through thin flooring or prevent rigid boards from sitting evenly. Deep depressions, actively moving cracks, and major falls are not solved by simply pouring more compound; those conditions need their own repair and level design.
Decide before pouring
Measure the actual floor and finished height before choosing the area and quantity.
- Whether the whole floor or only measured problem areas will be treated
- Highest and lowest points, average pour thickness, and required material quantity
- Clearance at thresholds and beneath doors after the new flooring is added
- Product, water ratio, working sequence, and the time the area must remain closed
Check in the quote
Material use changes with thickness, even when the floor area stays the same.
- Are the treated area, average thickness, and material quantity all stated?
- Are crack repairs, high-spot removal, vacuum cleaning, and primer included?
- Will door and threshold clearance be checked before the pour?
- Are bubble removal, curing protection, and a final flatness check included?
If you have floor photographs, straightedge readings, or a quote, I can help decide where self-levelling is justified and what preparation is missing.
What to check on site
Check all three stages before the final floor hides this layer.
- Substrate Cleanup and Primer Complete
The base should be free of dust and weak fragments. Repair cracks and high points first, then confirm that primer covers the full area and has reached the condition required by the product. - Leveling Pour and Bubble Removal Complete
Mix to the measured water ratio rather than adding water by eye. Adjacent batches need to be poured continuously, then rolled while workable to release trapped air. - Curing and Inspection Complete
A dry-looking surface may still be weak underneath. Keep traffic off for 24 to 48 hours, check the cured plane with a straightedge, and repair soft, hollow, or cracked areas before flooring begins.
Where problems usually start
- The layer lifting and cracking Dust or missing primer prevents the new compound from bonding to the base, so edges release and cracks spread.
- A surface that crushes under load Extra water makes the mix easier to spread but reduces cured strength until it powders beneath the finished floor.
- Craters left in the surface Air that is not released bursts at the surface and leaves pits that can show through thin sheet flooring.
- Cracks during curing Strong draughts or forced air dry the surface faster than the body of the pour, creating shrinkage stress.
Once the final floor is laid, this layer becomes difficult to inspect. Confirm both hardness and flatness rather than judging cure from colour alone.
Record the original floor, product and water ratio, pour thickness and time, curing conditions, and final straightedge check.
Timing and records
Allow about 4 to 8 hours for preparation and pouring, followed by a separate 24 to 48 hours of curing. Large areas may require more workers so wet edges can be joined before the mix begins to set.
Keep a room-by-room record of area and thickness, product quantity, substrate preparation, pour photographs, curing completion, and final flatness.
Start with the condition of the existing floor, then set the tolerance required by the flooring that will cover it.