Do I need to use an underlay under my railway track?

It is not essential to use an underlay for your layout, but it is definitely a good idea as the underlay will help to suppress the noise of your trains when running around the layout.

The underlay absorbs vibrations of the train running so you get to enjoy a quieter layout. This is especially important as baseboards are usually made of wood with a deep cavity underneath, making sound reverberate.

The other reason why you may want to want use underlay is cosmetic. The underlay raises the track which makes it look more like the real thing as real track sits on a bed of ballast.