If you're carrying out a double bond installation, you will lay the underlay first and then set out the working lines for the tiles on top of the underlay.

On the other hand, if you're doing a direct stick, you will skip the underlay installation and start setting out for the tiles on the subfloor surface (see the next lesson).

Before you apply adhesive to the subfloor to stick down the underlay, you'll need to plan the layout of the material and trim it to size.

You'll also need to give the underlay time to acclimatise to the humidity in the room, and 'relax' as its moisture content adjusts to the surrounding air.

Depending on the product and the manufacturer's recommendations, the acclimatisation period might be three hours or even overnight.

Installing the underlay

Trim the underlay to fit around the perimeter walls, and make sure any seams are butted neatly.

Fold one half of the underlay back on itself to expose the subfloor underneath.

Pour a quantity of adhesive on the floor and spread it with a notched trowel.

Make sure you use the correct trowel size, as specified by the adhesive manufacturer.

Remember to hold the trowel at 60 degrees to maintain the right consistency, and go right to the edges and into corners.

Wait for the adhesive to 'tack up', and then carefully lay the folded-back underlay into position on the adhesive.

Use the same procedure on the other half of the underlay.

Then trim in the underlay around the perimeter.

Most underlay manufacturers recommend that you use a roller - generally 25 to 35 kg - to roll out any bubbles or wrinkles.

Work from the centre towards the perimeter of the floor area and apply a smooth, even pressure.

Make sure the underlay seams are tight but not overlapping.