How to Fix Sagging or Uneven SPC Flooring Over Time
SPC flooring is dimensionally stable, but that does not make it immune to unevenness. If you notice sagging areas or a wavy surface months after installation, the cause is almost always the subfloor. This guide explains why it happens and how to fix it.
Why SPC Flooring Becomes Uneven
SPC planks are rigid. They do not conform to subfloor shape. If the subfloor has dips or bumps, the planks bridge over them. Over time, foot traffic causes the planks to settle into these depressions. The result is a visible sag.
Common causes include:
- Subfloor was not leveled before installation
- Plywood subfloor panels are different thicknesses
- Concrete slab has settled or cracked
- Moisture has caused the subfloor to swell in one area
- Poor subfloor preparation was hidden by thick underlayment
The rigid core of SPC actually makes this problem worse. Flexible LVT would follow the subfloor contour and not show the unevenness as visibly.
How to Identify the Problem Area
Walk the floor and mark all sagging or uneven areas. Press down on the sagging area. If it moves, the planks are not fully supported underneath. Use a long straight edge across the floor. Any gap between the straight edge and the floor indicates a low spot.
Check if the sagging is limited to one section or spread across the room. Localized sagging is usually caused by a subfloor defect in that specific area. Widespread unevenness indicates the whole subfloor was not prepped properly.
Solutions for Minor Sagging
For minor sags of less than 2mm, the cause may be natural subfloor movement. Wood subfloors expand and contract with seasons. The sag may resolve itself when humidity returns to normal levels.
Do not attempt to fill the gap by injecting foam or leveling compound under the planks. This can lift the planks and create a bump instead of a dip.
Solutions for Moderate Sagging
For sags of 2mm to 5mm, the floor needs to be lifted and the subfloor leveled. This requires removing the planks in the affected area.
1. Lift the planks starting from the nearest wall
2. Mark each plank with its position and orientation
3. Remove the planks until the sagging area is exposed
4. Check the subfloor for dips or damage
5. Apply self leveling compound to fill low spots
6. Allow the leveling compound to cure completely
7. Reinstall the planks in the same order and orientation
Floor leveling compound cures within a few hours. The planks can be reinstalled the same day in most cases.
Preventing Sagging During Installation
Sagging is preventable with proper subfloor preparation:
1. Check subfloor flatness before installation. Use a 2 meter straight edge. Fill any gaps over 3mm
2. Screw down loose plywood panels before installation
3. Check for squeaks and fix them, they indicate movement
4. Use the thinnest possible underlayment. Thick underlayment masks subfloor problems but does not fix them
About PROLEADER
PROLEADER provides detailed subfloor preparation guidelines with every SPC flooring order. Contact us for installation guides and technical support.
