Each shell was poured in situ with large wooden moulds that were dismantled and moved on to form the next one. This form was suggested by Arup as a suitable approach to the design. The other seven garages were never executed and the concrete moulds were destroyed after the completion of Donnybrook due to Government politics and the advice of a senior civil servant Dan O'Donovan. Externally the building's elevations are dictated by the roof form which is visible along the sides. Smaller flat roofed buildings were built next to it but do not intrude on the distinctive shape of the building.
Decorative ribs are visible along the side elevations.
Originally it was coloured externally in a grey and yellow paint scheme designed by Patrick Scott, which has since been painted over. Internally the garage is an imposing well-lit internal space uninterrupted by columns or internal walls.