There are different methods for securing hard underlays to the subfloor, depending on the materials involved.

The manufacturer's recommendations should always be followed, unless you know for a fact that an alternative method will achieve an acceptable result and would be approved by the manufacturer in the event of a warranty claim.

Below are some common types of fixings used with hard underlays.

Staples

Staples are used in conjunction with adhesive to fix hard underlays to timber or wood-based subfloors.

They are generally 22 mm minimum length, and are galvanised or copper etched and resin coated.

Nails

Nails are used when fixing to soft subfloor timbers, such as radiata pine and Baltic pine, because they have better holding power than staples.

They are generally 25 x 2 mm diameter and often ring grooved.

Adhesives

Adhesives include neoprene type wallboard, construction grade or PVA adhesives.

They are used in conjunction with stapes or nails when fixing to structural sheet flooring, such as plywood, particleboard and fibre cement.

Screws

Screws are often used with thicker plywood or fibre cement underlay sheets, or when fixing to unusual substrate materials such as steel.

Their length will depend on the thickness of the underlay and holding power required.

Specialty fasteners

There are various fasteners available for fixing underlay sheets to concrete subfloors, such nylon anchors (above left) and split drive anchors (below left).

Many of these fasteners are referred to by their brand name.