If by tiles you mean each space on the floor - they are standard 1" or 25mm scale spaces. Dwarven Forge pieces are all the same height - and I don't have one handy, but they're taller than the common plaster molds (Hirst Arts etc.) produce. As seen they're just tall enough to hide away most normal 25/28mm miniatures.
In some rooms, as shown in the photos, there is an additional "half-space" against the walls. On some pieces this is not present. Given that 1" or 25mm is a normal size, miniatures fit well, but any larger or very dynamic poses may cause an issue for ya.