The houses of Donegall Street are in the, well proportioned, simple style common to Georgian architecture with the main detailing being reserved for the door surrounds. Also typical of Georgian townhouses, Donegall Street homes are spread over four floors with three above ground and one below (although at the rear all four floors are at ground level).
As brickworks opened around Belfast in the latter part of the 18th century it began to replace stone in the creation of new homes, a feature that would continue into the Victorian period. Stone had been employed as it could be sourced locally and now brick was available locally too.
Windows of Georgian townhouses were usually proportioned according to the hierarchy of function behind. Living space had large windows and sleeping and servants space had small windows. This is not the case in Donegall Street but can be seen here. As there was no electricity to light these spaces larger windows were used to allow in maximum levels of light.
Using brick from a local source is more sustainable than using imported brick that will have travelled long distances.
Building with large windows in living spaces, like the Georgians did, means you do not need to switch electric lights on quite as much.