There are several instances in the literature in which particular positions are taken regarding the nature of the floor supporting sensitive equipment such as advanced electron microscopes. Assertions are made that one methodology is better than another at reducing vibrations. However, very little experimental evidence has been provided to support those positions. This paper presents the results of an experimental <i>in situ</i> study of several slab configurations at a single location-the site of a nanotechnology facility that was about to be constructed at the University of Alberta. Three configurations were constructed: (a) a large solid slab of moderate thickness; (b) a smaller slab "island" of greater thickness (900 mm) surrounded by a thinner slab, both resting directly on soil and separated by a gap; and (c) another island of the same dimensions, but resting on four concrete piles. The three locations were instrumented and measurements taken allowing comparison of the performance of these configurations at attenuating ambient vibrations and vibrations due to a nearby heel-drop impulse. The ranking of the three must be based upon excitation type and frequency range of concern.