COMPANY - COLWIS. Colwis Corp. is a privately owned company, operating out of Richmond Hill, Ontario and serving the GTA and Ontario. Our services include General Contracting, Construction Management, Project Management, Design Build, Land Development, Electrical & Mechanical Subcontracting, Formwork Subcontracting and Electrical Supplies to various private, public, and government clients. Our projects range from commercial, institutional, industrial, high-rise residential and hi-rise retirement residences.. Colwis Corp, Colwis Corporation, Colwis,company, Richmond Hill, Ontario, Toronto, GTA, Ontario, General Contracting, contractor, subcontracting, subcontractor,construction, management, Construction Management, project, Project Management, building, Design Build, Land Development, Electrical, Mechanical, Formwork, Formwork Subcontracting, Electrical Supplies, private, public, government, projects, commercial, institutional, industrial, high-rise, residential, retirement residences, home.