Whether vinyl flooring needs underlay depends on the type of vinyl and the subfloor's condition.
'Underlay can provide comfort, insulation, and sound reduction, but in some cases, it's not necessary,' says Andhi from MyProsAndCons. 'If you're laying sheet vinyl over a smooth, well-prepared subfloor, you might not need underlay. But if you're using luxury vinyl tiles or planks over a hard subfloor, an underlay with soundproofing and moisture barrier properties could be beneficial.'
The most important thing is that your floor is completely level before you apply vinyl. Most types of vinyl will glue down smoothly and permanently, so a underlay isn't necessary if you've already got the perfect base.