Real estate development and redevelopment; refurbishment and renovation of buildings; conversion of buildings in the nature of building renovation; construction of buildings; installation of roofing, windows, window fittings, window frames, ceilings, central heating, building insulation, scaffolds, pipes, plumbing, electrical wires and switches; building maintenance and repair; cleaning of buildings; janitor services in the nature of cleaning of buildings; onsite maintenance and repair of apartment buildings; information and advisory services relating to the aforesaid