Do I need a Foundation for a Wall to Replace old Asbestos Building? All manner of questions and solutions to problems and issues surrounding the subject of brickwork, blockwork and stonework

[Mightygrecian]

I intend to replace an old asbestos out building with a new one built with brick and timber. My question is, as I have an existing concrete base do I need to dig foundations for a wall measuring approx 2-2.5 meters high or just build on what I already have?