Why do I need to use underlay under my track?

The main reason for using underlay is to help to reduce the noise on your layout. If you run your train on track placed directly on wood, it resonates a lot and this is amplified by the void under the baseboard.

The second reason is by putting underlay under the track, this will raise the track slightly and give a more realistic look when adding ballast.

If you look at the real thing, the ballast is at least 6in (15cm) deep and can be up to 12in (30cm) deep. Obviously, with model railways, we do not need to use ballast for the same reasons, but raising the track will create the same look.