The Town Hall Extension, housing municipal departments including rates, rents and street cleaning departments, was built after a competition in 1927 was won by E. Vincent Harris who, in the same year, won a competition to build Manchester Central Library on an adjacent site.
 The building, built by J. Gerrard & Sons Ltd of Swinton, is essentially Gothic in character, with ornately carved tracery and a steeply pitched roof interpreted in a contemporary style.
The building was started after the Central Library was completed and originally had a rates hall, gas and electricity showrooms on the ground floor; a cinema was built at basement level and on the first floor is a council chamber.
The building cost £750,000 and was opened by King George VI in 1938, the occasion commemorated by a carved inset stone at the Mount Street end.

The building is linked to Manchester Town Hall by two covered bridges at first-floor level over Lloyd Street and has an irregular plan with a concave south side facing the Central Library.
Its curved four-storey range with round-headed arches and small windows facing Library Walk is 200 feet in length.
The eight-storey building has attics and a basement.
It was constructed with a steel frame clad in ashlar sandstone from Darley Dale and a steeply pitched slate roof.
The Lloyd Street facade has 29 windows, five of which are set back and its seventh and eighth storeys are set behind a parapet.
The 17-window facade to St Peter's Square has small rectangular windows up to the parapet and two-light mullioned windows to the sixth and seventh floors, and its attic dormers have hipped roofs and wooden cross-windows.
Along these facades, on the ground floor, is a continuous arcade of plain round-headed openings and a chamfered coping.
The upper floors on the Lloyd Street and St Peter's Square facades have a horizontal band over the first floor.
The Mount Street facade has five large oriel windows filled with mullion-and-transom windows.
The gable ends on Mount Street and St Peter's Square have stair-turrets with round-headed arches containing windows with geometric tracery.
Above them are niches with statues.
Its stained-glass windows representing Lancastrian coats of arms were designed by George Kruger Gray.

Charles Reilly, a contemporary architecture critic, thought the extension was 'dull' and 'drab' while Nikolaus Pevsner considered it was Harris's 'best job'.
The Town Hall Extension, housing municipal departments including rates, rents and street cleaning departments, was built after a competition in 1927 was won by E. Vincent Harris who, in the same year, won a competition to build Manchester Central Library on an adjacent site.  The building, built by J. Gerrard & Sons Ltd of Swinton, is essentially Gothic in character, with ornately carved tracery and a steeply pitched roof interpreted in a contemporary style. The building was started after the Central Library was completed and originally had a rates hall, gas and electricity showrooms on the ground floor; a cinema was built at basement level and on the first floor is a council chamber. The building cost £750,000 and was opened by King George VI in 1938, the occasion commemorated by a carved inset stone at the Mount Street end.
The building is linked to Manchester Town Hall by two covered bridges at first-floor level over Lloyd Street and has an irregular plan with a concave south side facing the Central Library. Its curved four-storey range with round-headed arches and small windows facing Library Walk is 200 feet in length. The eight-storey building has attics and a basement. It was constructed with a steel frame clad in ashlar sandstone from Darley Dale and a steeply pitched slate roof. The Lloyd Street facade has 29 windows, five of which are set back and its seventh and eighth storeys are set behind a parapet. The 17-window facade to St Peter's Square has small rectangular windows up to the parapet and two-light mullioned windows to the sixth and seventh floors, and its attic dormers have hipped roofs and wooden cross-windows. Along these facades, on the ground floor, is a continuous arcade of plain round-headed openings and a chamfered coping. The upper floors on the Lloyd Street and St Peter's Square facades have a horizontal band over the first floor. The Mount Street facade has five large oriel windows filled with mullion-and-transom windows. The gable ends on Mount Street and St Peter's Square have stair-turrets with round-headed arches containing windows with geometric tracery. Above them are niches with statues. Its stained-glass windows representing Lancastrian coats of arms were designed by George Kruger Gray.
Charles Reilly, a contemporary architecture critic, thought the extension was 'dull' and 'drab' while Nikolaus Pevsner considered it was Harris's 'best job'.
Manchester Town Hall Extension