How Do You Lay Underlay Tiles?
While the term "underlay tiles" is not standard for flooring underlayment, which typically comes in sheets (like plywood or fibre-cement board) or rolls, the process of laying sheet underlayment (often used as a stable base before installing tiles over a timber floor) involves specific steps to ensure a proper foundation. Based on common practices for sheet flooring substrates, here's how you approach installing underlayment sheets.
Installing the correct underlayment is a critical part of preparing a subfloor for tiling, particularly over existing timber floors. Sheet underlayment provides the necessary rigidity and smooth surface required for tile adhesive and grout lines. Follow these steps for effective installation:
1. Prepare the Subfloor
Before laying any underlayment, ensure your existing timber subfloor is clean, dry, level, and securely fastened. Address any squeaks, loose boards, or significant unevenness.
2. Plan Your Layout
Determine the best starting point and layout for your underlayment sheets to minimize cuts and optimize material use.
3. Lay the Underlayment Sheets
This is where the specific guidelines for sheet flooring substrates come into play:
- Direction: Sheets are laid perpendicular to the direction of the main flooring substrate, such as timber floorboards.
- Joint Offset: It is crucial as joins must not coincide with the joints in the timber floor. A minimum offset of 100mm is required between the underlayment sheet joints and the timber floor joints. This helps prevent weakness and potential cracking of the finished tile floor along the subfloor joints.
- Wall Gap: Ensure the edges of the underlayment sheets are 3mm back from walls and other fixed vertical surfaces. This allows for slight expansion or movement.
4. Secure Sheets Temporarily
To prevent the sheets from shifting out of place while you complete the layout or before permanent fastening:
- Temporary Fix: Temporarily fix each sheet with two or three nails to avoid movement.
5. Permanent Fastening (Manufacturer Specific)
While the reference mentions temporary fixing, sheet underlayment typically requires permanent fastening according to the manufacturer's instructions. This often involves specific screws or nails spaced at recommended intervals across the sheet and along edges. Consult the underlayment product documentation for these critical steps.
Why This Process Matters
Following these steps ensures that the underlayment creates a strong, stable, and uniform surface for your tile installation. Laying perpendicular and offsetting joints distributes load effectively, reducing stress on the subfloor and the final tile layer, which helps prevent common issues like cracked tiles or grout lines over time.
Properly installed sheet underlayment is an essential foundation for a successful and durable tiled floor, especially when placed over a timber subfloor.
