The Natural History Museum was Waterhouse's first attempt at this relatively new medium. He boldly decided to face the entire building in terracotta, the first example of such cladding. By the 1890s terracotta had become a regular ornamental feature on steel framed buildings in both Britain and USA, but at this time Waterhouse was a pioneer.

Waterhouse liked the medium for its durability, cheapness and washable qualities. As an artist he also liked the variety of colours and tints produced from firing. Another possible reason for his choice, particularly in light of general opposition to the medium and preference for carved stone, was that unlike stone terracotta was structural as well as a facing material.

Justifying the use of ornamentation

To work within the museum's tight budget it was useful to argue that the ornament could not be rejected as it served a structural role. Stone on the other hand is carved after construction therefore it would be easy to withhold funds for such decoration. The use of terracotta was also in keeping with other buildings in South Kensington, in particular Cole and Fowke’s South Kensington Museum.

Waterhouses's working drawings

This drawing of 1875 is an excellent example of a working drawing. It includes a plan, section, elevation, perspective detail, and moulding profiles, giving as much detail as possible to enable the structure to be built. Working drawings are used on-site, hence they can become soiled and damaged as this example shows.

The drawing also demonstrates Waterhouse's attention to detail, and in particular his concern with materials. On it he notes how the materials used for the main staircase must match as closely as possible, and draws attention to possible problems with shrinkage of the terracotta.