What is an underlay?
An underlay is a thin layer of material that essentially acts as a middle layer between your subfloor and the hardwood floor or carpet that you are about to install. There are different types of underlay that can be used with hardwood flooring, depending upon your needs and requirements. The most popular uses for underlay are for thermal resistance and sound proofing.
Underlays for thermal resistance
Underlays which are designed for thermal resistance all have a tog rating. The higher the tog, the more effective the underlay is in providing warmth and insulation. When using hardwood flooring with an underlay, a good tog rating to provide adequate thermal resistance is 1.0 tog. However, different floor coverings require underlays with different tog ratings, for example, an underlay used with a carpet should be at least 2.5 tog.
Underlays for sound proofing
Underlays which are designed for sound proofing all have a decibel (dB) rating. The higher the rating, the more sound reduction they will provide. A sound proofing underlay has two jobs; reduce the noise in the room itself and reduce any transference of sound to rooms below. When using hardwood flooring a good quality sound proofing underlay would have a rating of around -25 dB, whereas a standard sound proofing underlay would be approximately -19 dB. If using a carpet then it is recommended that the sound proofing underlay has a rating of between -39dB and -46dB.
Underlays for underfloor heating
Underlays for underfloor heating have been designed to have a low tog rating to provide the least thermal resistance allowing the heat from the underfloor heating to transfer to the hardwood floor. An underlay specifically designed to be used with underfloor heating should have a tog rating of approximately 0.35 tog.
Is a thicker underlay better?
No, the thickness of the underlay does not make any different to the thermal resistance or sound proofing. You should always look at the tog or decibel rating.
Does the colour of the underlay make a difference?
No, the colour of the underlay does not make any different to the thermal resistance or sound proofing. You should always look at the tog or decibel rating.
Can I use an underlay to level out my subfloor?
No, an underlay should never be used to level out an uneven subfloor. Separate products are available for this. For further information about preparing your subfloor, please see: ‘How to prepare my subfloor before installing hardwood flooring.’
