Whether you're fitting carpet, laminate or wood flooring, underlay is an essential step in achieving a quality finish. Not only does it improve insulation and soundproofing, but it also helps prolong the life of your flooring by providing a stable and even base. In this guide, we’ll walk you through how to lay underlay in compliance with British standards and regulations.

What You’ll Need:

• Underlay (appropriate for your flooring type)
• Craft knife or utility knife
• Tape measure
• Underlay tape or masking tape
• Scissors
• Staple gun or adhesive (for certain types of underlay)
• Knee pads (optional but highly recommended)

Step 1: Prepare the Subfloor

Before you begin, make sure the subfloor is:

• Clean – Sweep or vacuum thoroughly to remove dust and debris.
• Dry – Moisture can damage flooring and underlay. Use a damp meter if in doubt.
• Level – Fill any holes or cracks and sand down raised areas.

Allow any new screed or concrete to cure fully before laying underlay.

Step 2: Choose the Right Underlay

Different floor types require different underlays. For example:

• Carpet underlay tends to be thicker and softer, offering better cushioning.
• Laminate and wood underlay is typically thinner and may include a damp-proof membrane (DPM) or sound insulation layer.

Make sure your underlay is suitable for both your flooring and subfloor type (concrete, timber, etc.).

Step 3: Lay the Underlay

For Carpet:

• Start in one corner of the room and roll out the underlay, rubber side down (if applicable).
• Butt the edges together – do not overlap – and trim to fit the shape of the room.
• Use underlay tape or staples to secure the seams and edges. On concrete subfloors, adhesive may be needed.
• Continue laying in strips until the entire floor is covered.

For Laminate or Wood Flooring:

• Roll out the underlay perpendicular to the direction of the floorboards.
• If the underlay has a built-in DPM, ensure the plastic overlaps the edges by at least 20cm.
• Butt the edges together and tape all seams with waterproof underlay tape.
• Avoid creases or overlaps, as these will affect the final flooring.

Step 4: Check Your Work

• Before installing your flooring:
• Ensure the entire floor is covered, with no gaps or overlaps.
• Check for a smooth, even surface throughout.
• Make sure all joins are securely taped or fastened.

Final Tips:

• Always follow the manufacturer’s instructions for both your underlay and flooring.
• If you're installing underfloor heating, make sure the underlay is compatible.
• Use a moisture barrier if installing over concrete.