How to Lay Carpet: Floor Preparation, Underlay and Stretch-in Installation

Laying carpet requires method but remains within the reach of any patient DIYer. The key to a successful installation lies in the floor preparation, the choice of a good underlay and the use of the right knee kicker. In this guide, we explain how to lay carpet from A to Z: substrate diagnosis, planning the strips, stretch-in installation on gripper strips and finishing the seams for a clean floor, free of creases and bubbles.

Preparing the floor before laying the carpet

The substrate must be clean, dry, flat and stable. On a concrete floor, fill the cracks with filler powder and treat rising damp with a primer. On a wooden floor, check that no board is loose and screw down any that move. A floor with holes deeper than 3 mm must be levelled with a self-levelling compound before installation. Finally, vacuum carefully: even the tiniest grain is felt under the carpet and causes visible bumps.

The essential equipment

• A utility knife with a reinforced blade and spare blades (very sharp)
• A knee kicker and a protective knee pad
• Gripper strips (U or L shaped) and a hammer
• An underlay (foam or felt) and seam joining tape
• A tape measure, chalk or marker, a folding rule
• A 2 m aluminium straightedge for straight cuts
• A seam iron or a joint roller for joining the strips

Laying the underlay and planning the strips

Roll out the underlay in the direction of the room, without overlapping, and tape the strips together. On concrete, add a vapour barrier. Then plan the carpet: always start from a straight reference wall and lay the first strip along the axis of the room, leaving 5 to 8 cm overhanging on each wall. The strips are all laid in the same direction, taking account of the pile direction: run your hand over the carpet, the pile should "flow" in the direction of the natural traffic flow of the room.

Fixing the gripper strips

The gripper strips are laid 5 mm from the walls, pins facing the carpet, along all the walls and posts. Nail or screw them depending on the substrate, joining them end to end. At doors and passages, you need a threshold strip: this is what receives the carpet for a clean finish at the doorway. Check that all the pins are well raised towards the inside of the room: a flattened pin tears the carpet during installation.

Laying and stretching the carpet

1. Unroll the first strip over the whole room, letting it overhang 5 to 8 cm on the walls.
2. Press the carpet onto the pins of one wall with the palm of your hand or a trowel, without cutting it yet.
3. Stretch the strip towards the opposite wall with the knee kicker, pushing in successive small strokes of 5 to 10 cm.
4. Mark the corner in pencil by pressing into the angle, then cut along the wall with the utility knife leaving a 5 mm gap.
5. Fold the carpet back into the corner and hook it onto the pins of the gripper strip.
6. Repeat the operation strip by strip, then trim the excess using the straightedge and a new utility knife blade.

Joining the strips and finishing the corners

For an invisible seam between two strips, overlap them by 2 cm, cut through both thicknesses together with the utility knife against a straightedge, then remove the offcuts. The two strips then fit together perfectly. Stick a heat-activated seam tape under the joint and run the seam iron at 120 °C along the seam. For the wall corners, make a V-cut from the edge of the carpet to the corner point, fold over, stretch and cut: the result is clean with no crease.

The mistakes to avoid

• Laying the carpet on a damp or poorly levelled floor: damp rises and makes the underlay buckle.
• Ignoring the pile direction: strips laid in opposite directions look striped.
• Cutting the carpet too tight: 5 cm of overhang is better than a bad seam.
• Neglecting the 24-hour relaxing time: the creases reappear at the first change in temperature.
• Using a blunt utility knife: it tears the backing of the carpet instead of cutting cleanly.

Laying carpet is within the reach of a motivated DIYer, provided the preparation is serious and the kicker is used correctly. Prepare the floor, plan your strips, let the carpet relax then stretch it in small successive strokes: you get a smooth, warm, comfortable floor. For a large room or a staircase, the best option remains calling in a professional fitter: the equipment and know-how make the difference on complex cutouts.