How to Level a Wooden Sub Floor?
To level a wooden sub floor, you address high spots (humps) by sanding them down and fill low spots (dips) using a two part latex leveling compound, ensuring no deviation exceeds 6 mm (1/4 inch) over 3 meters (10 feet).
A level sub floor is crucial for the proper installation and longevity of almost any finished flooring material, from hardwood and laminate to tile and vinyl planks. Unevenness can lead to creaks, cracks, or poor adhesion.
Manufacturers recommend that the sub-floor is sufficiently level. Specifically, over a span of 3 meters (10 feet) there should not be any dips or humps greater than 6 mm (1/4 inch). Achieving this standard requires addressing both raised areas and depressions.
Addressing High Spots (Humps and Raised Areas)
High spots or humps on a wooden sub floor are typically caused by irregularities in the wood panels or structural issues beneath.
- Identification: Use a long straight edge (like a 3-meter/10-foot level or a straight board) laid across the floor to identify raised areas.
- Method: Small humps and raised areas can be sanded down with a belt or orbital sander.
- A belt sander is more aggressive and suitable for larger or more significant humps.
- An orbital sander is better for smaller imperfections or smoothing the area after belt sanding.
- Process: Slowly work the sander over the high spot, checking frequently with your straight edge until the area meets the levelness standard. Always wear a dust mask and safety glasses when sanding.
Filling Low Spots (Dips and Depressions)
Low spots or dips are often caused by settling, uneven sub floor panels, or damaged areas.
- Identification: Use a straight edge as described above. Dips will show a gap between the sub floor and the straight edge.
- Method: To level any dips you should use a two part latex leveling compound.
- This type of compound is specifically designed for flooring applications and adheres well to wood sub floors.
- Being "two-part latex" means it likely involves mixing a liquid latex additive with a dry cementitious powder, creating a strong, flexible filler suitable for wood.
- Process:
- Clean the dip area thoroughly of dust and debris.
- Follow the manufacturer's instructions precisely for mixing the two-part compound.
- Pour or trowel the mixed compound into the dip, slightly overfilling it.
- Use a trowel or screed (a straight edge) to level the compound flush with the surrounding sub floor.
- Allow the compound to cure fully according to the product's instructions before proceeding with flooring installation. Drying times can vary based on thickness and humidity.
Summary of Leveling Methods
| Problem | Method | Tool/Material |
|---|---|---|
| High Spots (Humps) | Sanding Down | Belt Sander or Orbital Sander |
| Low Spots (Dips) | Filling with Leveling Compound | Two part latex leveling compound |
By addressing both high and low points using these methods, you can prepare your wooden sub floor to meet the required flatness standard, ensuring a successful and durable finish flooring installation.
