Underlay and Moisture Membranes

Underlay and moisture membranes are a very important component of any laminate flooring installation. The underlay is usually placed directly on top of the sub-floor and forms a light cushion between the sub floor and the laminate. It also helps smooth out any small unevenness on the sub-floor and provides some degree of sound deadening and insulation - depending of the quality and type of underlay employed.

In addition to the underlay there is normally a need to fit a second protective layer under the laminate. This is referred to as the Moisture Membrane and role is to help prevent the ingress of moisture or rising dampness into the wood laminate.

Sometimes, the underlay and the moisture membrane are combined into one composite material referred to as a “combination underlay”. In South Africa most sub floors are concrete, and if the concrete slab is in direct contact with the ground, it may draw moisture out of the soil into the slab. Therefore, the selection of a quality Moisture Membrane is a very important matter.

What is vital that the membrane be manufactured using a virgin plastic (that is first time used plastic with no recycled component), this ensures that there is no degradation of the membrane. Recycled plastic is unacceptable because it does, by law in South Africa, contain a bio-degradable component, which will effectively cause the membrane to break up and degrade under the dark floor, rendering it useless.

BLACK PLASTIC is often found in use as a membrane; take care because the likelihood is that this is a re-cycled plastic. Plastic for membranes should be clear or at best slightly milky in colour to be sure that they are made from virgin plastic. Always ask for proof or origin of the raw materials used for membrane manufacture.

Failure to fit the correct quality of underlay and membrane can result in a failed installation. All laminate manufacturers will automatically reject any warrant claim, resulting from the use of the incorrect membrane material. So selection of the correct membrane is critical if one is to avoid problems later.

Sound Reduction

Noise absorption or reduction, especially on an upper-floor, is important to help deaden footstep sound being transmitted to the room below. It is also useful in quieter areas such as bedrooms or home office where a quieter environment is desirable. Acoustic types of underlay come in a variety of soft or hard components.

Softer variations consist of cork, foam, felt, fibre or rubber. Whilst cork provides a high quality of sound absorption and is insect repellent, however cost is a serious restriction to its common use.

Rubber sheet is a good option as a quality reasonably priced product that performs well at all levels and makes for an excellent installation. This is highly recommended for our more expensive products where the cost variance between the standard expanded foam and rubber is a relatively small additional cost.