An Taisce, a heritage organisation, opposed the larger designs, claiming that they showed disrespect for Eccles Street, which was built in the Georgian era. An Taisce also said that the hospital's design did not match the area's significance.
The development would be adequately situated, have a "good influence" on Eccles Street and the north Georgian centre of Dublin, and would not distract from the setting of any protected structures there, according to An Bord Pleanála's judgement.
The hospital stated in its submissions that the Covid-19 pandemic demonstrated the need for hospitals to deal with infectious disease better, with the Mater's current facilities remaining "under significant pressure" earlier this year during examination of the issue, according to planning inspector Stephen J. O'Sullivan.
He added that the land is not zoned for uses such as hospitals, but rather for uses such as "remedying this deficiency," which is a priority under national, regional, and municipal planning policy.
The new emergency wing "would considerably boost the hospital's ICU capacity and provide specialist isolation rooms for the care of extremely contagious patients," according to planning consultants hired by the Mater.
An Taisce, however, claimed that the proposed development "should be rejected approval or severely changed in its design and scale" in a submission made to the city council.
An Taisce said that the idea "undermines the basic premise of Georgian urban design which is built on calm and ordered streets, common parapets, height to width ratios, and cohesive vistas and termination points" in a prior submission to Dublin City Council.
It said that the application site, which faces Eccles Street, is at a crucial position and is a portion of a place where original Georgian homes were contentiously torn down in the 1980s.
As Ireland prepared for a third wave of Covid 19 in December 2020, The Mater started enabling works on the project under emergency law without the need for planning permission.
The Irish Georgian Society had "serious misgivings" about the idea in a separate submission, stating that its size would dominate Eccles Street.
O'Sullivan stated that the society's request to restore the previous streetscape in this manner would not be feasible in light of this.
Instead, the hospital will create a new entrance from Eccles Street and "increase the visual presence" of the hospital there.
"The proposed construction would blend in nicely with the streetscape. As a result, it would enhance the surroundings of the protected structures across the street, according to O'Sullivan.
The approval of the works was subject to a number of requirements, some of which were designed to safeguard street amenities while they were being built.