Designed by Thomas Stent and Augustus Laver,[2] the West Block is an asymmetrical structure built in the Victorian High Gothic style, with load bearing masonry walls, all clad in a rustic Nepean sandstone exterior and dressed stone trim around windows and other edges, as well as displaying a multitude of stone carvings, including gargoyles, grotesques, and friezes, keeping with the style of the rest of the parliamentary complex.

After the entries were narrowed down to three, then Governor General Sir Edmund Walker Head was approached to break the stalemate and the winner was announced on 29 August 1859.

The departmental buildings, Centre Block, and a new residence for the Governor General were each awarded separately and the team of Thomas Stent and Augustus Laver, under the pseudonym of Stat nomen in umbra, won the prize for the first category.

Scaffolding and protective sheeting were erected in order to prevent falling blocks from striking pedestrians and cars below and a restoration project was immediately implemented.

Multiple underground levels as well as planned tunnel connections to other Parliament Hill buildings were constructed out of dug-out bedrock under the West Block during the extensive renovations.