An underlay is a thin material that goes in between the existing floor in your property and your hardwood floor. There are many different types of underlay that can be used when fitting your hardwood floor. You will only need to use an underlay if you decide to float (or loose lay) engineered hardwood flooring.
Solid hardwood flooring needs to be fixed into position so must be glued or nailed directly to the subfloor. If you wish to float your engineered hardwood over an underlay you must have a solid, level subfloor like concrete or wooden floor boards (not joists), and you must decide which underlay is best for your needs. The most common uses for underlay are for thermal resistance, sound proofing or underfloor heating. Thermal resistance underlays A thermal resistance underlay will have a tog rating which helps to determine how effective the underlay will be in providing insulation and warmth. Generally, the higher the tog, the more thermal resistance the underlay will have. With hardwood flooring an adequate tog rating would be 1.0 tog.
Sound proofing underlays
Sound proofing underlays will have a decibel (dB) rating which help to determine the amount of sound reduction they will provide. The higher the dB rating, the more sound proofing it offers. Sound proofing underlays have two main jobs. Firstly they will help to reduce the noise in the room and secondly they will help to lessen any sound transferring to rooms below. With hardwood flooring a good quality sound proofing underlay would have a decibel rating of between -19 and -25 dB.
Underfloor heating underlays
here are specific underlays to be used with underfloor heating which have a low tog rating in order to allow the heat from the underfloor heating system to be transferred through to the hardwood. A tog rating of around 0.35 tog would enable this transfer of heat.
