Change happens to every building, as styles and standards evolve. Where to draw the line between preservation and evolution is a matter of judgement and taste. An example of this was the abatement of asbestos floor tile from a concrete floor in a classic mid century modern residence, by the noted architect Samuel Glaser.

Mid century concrete floor.
Materials go in and out of style, as tastes and building standards change. No material has been more subject to this cycle than asbestos fiber. Strong and lightweight asbestos fiber was added to many construction materials from the nineteenth century through the 1970’s when use tailed off as it was proven that dust from the material causes cancer.
This was not a concern when this house was constructed in 1949. Both the tile itself and its adhesive contained asbestos and were completely abated as part of our addition and renovation project. After removal, we noted that the tile had left a characteristic “shadow” pattern in the concrete.
This shadow, we told the owners, could be polished away. They declined, noting that not only was the pattern interesting, but it was historic, so we kept it. We stained the concrete throughout, in order to coordinate the new and existing flooring and otherwise left the pattern as it was, subtly referencing the original intention of the architect.