The importance of accuracy

Neil Sanders of F. Ball and Co. reveals why accurate moisture testing and management is key to preventing flooring installation failures.

Unmanaged subfloor moisture is one of the most common causes of failure in a flooring installation. Over time, excess moisture can cause irreparable damage to any type of floor covering. If excess moisture isn’t tested for, or correctly dealt with, damp can cause adhesives to de-bond, carpet underlays to rot, wooden floors to warp, and resilient floor coverings to blister, ultimately causing the installation to fail. Usually, this may only be resolved through costly remedial work.

The first stage of any flooring project, whether installing a floor covering in a new building or refurbishing an existing floor, is to take the time to thoroughly assess the composition and condition of the subfloor before specifying the correct subfloor preparation products. Excess subfloor moisture in particular, when left untreated, may also promote the growth of mould, which can cause certain floor coverings to discolour and risk further damage to the floor covering. This can easily be avoided by using modern, waterproof surface membrane systems.

Moisture testing

There are a number of options of moisture measurement tools that can be used to test the moisture levels in a subfloor. Small, hand-held meters which use a non-invasive, pinless radio frequency can be used to detect moisture directly in materials and below wall and floor coverings such as tile, wood and vinyl. Moisture measurement systems can be used for surveying buildings, inspecting a home, drying a building after a flood, or testing concrete moisture for a flooring application.

A calibrated digital hygrometer is a moisture measurement method used to assess subfloor moisture levels as a measure of relative humidity (RH), and will indicate whether a moisture management system is necessary. It incorporates a thermo hygrometer that indicates both relative humidity and air temperature to provide an accurate measure of the moisture levels present in a subfloor.

Measurements should be repeated at various points across the floor as necessary. Once enough time has passed to allow the entrapped air to reach moisture equilibrium with the subfloor, the hygrometer can be switched on and a reading taken.

The readings from the hygrometer should inform the next steps taken. If the readings indicate RH levels of less than 75 per cent (or 65 per cent for wood flooring installations) no further steps need to be taken, as the subfloor is sufficiently dry for the installation to continue as planned. However, if the readings are above 75 per cent or 65 per cent respectively, a waterproof surface membrane must be installed before proceeding with the installation.

There are a number of options available should protection against excess moisture be required. Contractors can use a waterproof surface membrane or loose-lay  isolator membrane to provide a barrier between excess moisture in subfloors and floor coverings, impeding the passage of damp.

Waterproof surface

Leading waterproof surface membranes come in the form of a one-part, two coat water-based system and a two-part single coat system. Waterproof surface membranes impede the passage of residual construction moisture and rising damp from affecting subsequent floor covering installations. This allows for the early installation of floor coverings in fast track building programmes.

A one-part, two-coat waterproof surface membrane system can be used to isolate moisture where RH values are up to 95 per cent. The technology behind these systems means that when cured, a waterproof film is created over the surface of the subfloor, effectively suppressing any excess residual construction moisture. Each coat of the waterproof surface membrane will be dry within 30 minutes, after which the flooring installation can proceed without delay.

Such a system can be used to isolate residual construction moisture where Relative humidity values are up to 98 per cent. They can allow for the early installation of floor coverings in fast-track new build programmes, without having to wait for the concrete subfloor to dry, and provide excellent moisture protection to areas subjected to high levels of damp, or where a large amount of excess moisture is present.

Isolator membranes

Alternatively, a loose-lay isolator membrane can be laid directly onto the subfloor to provide a barrier between moisture and the floor covering. Loose-lay membrane systems are also ideal for use with heritage floors, because the membrane allows a new floor to be adhered to its upper surface while protecting the floor beneath. By acting as a base to receive resilient floor coverings and carpet tiles, loose lay isolator membranes allow durable new floors to be installed and easily removed at a later date, so buildings can be returned to their original state.

An isolator membrane is an impervious loose lay separator sheet designed to be laid over damp or contaminated subfloors prior to the installation of a wide range of sheet vinyl, linoleum, rubber floor coverings and bitumen backed carpet tiles. It provides a moisture barrier over damp subfloors and provides a protective barrier over floors that cannot be prepared by traditional methods due to surface contamination, such as oil, grease or paint, without the use of extensive mechanical surface preparation techniques. The membrane has nodules on the underside to create an airspace allowing vapour to travel to the edge of a room, into a dry wall, or a ventilated area, where it can safely escape.

Unmanaged moisture can cause adhesives to debond, wood floor coverings to warp and other flooring failures that compromise the aesthetic appearance or cause the flooring installation to fail. Accurate moisture testing and management is the best defence against flooring failures.

Neil Sanders is technical director at F. Ball and Co