No subfloor is perfectly level, but any signs of unevenness and high or low spots must be remedied.
Please follow these requirements:
- Subfloor unevenness cannot be greater than 3/16 of an inch over a 10 foot span or 1/8 inch over a 6 foot span
- Not slope more than ½ inch per 6 feet (25 mm per 1.8 m)
- Be structurally sound
Making a substrate level
- Concrete substrate: use a portland cement or gypsum based floor patch
- Plywood substrate: use a portland cement based floor patch
Before installing flooring over existing ceramic tile
Use a portland cement based floor patch to fill the grout joints and raise any low spots to level.
Is a flat subfloor important with the types of flooring installation listed below?
Glue Down LVT flooring
Yes. It measures only 2-3 mm thick. Thin and flexible, it telegraphs imperfections in the subfloor not remedied before installation.
No. Rigid vinyl planks like Sound-Tec and SurfaceGuard float over minor subfloor imperfections. They mask subfloor unevenness. However, because of the precisely milled clip system, a flat substrate is recommended for support.