Businesses involved in the construction of commercial buildings deliver projects such as offices, shops, warehouses, factories, hotels and other premises used for business or public services. Work may include building new premises from the ground up, extending existing buildings or carrying out major structural alterations. Projects are usually based on architectural and engineering designs and may involve coordination with clients, consultants, suppliers and specialist trades. Typical services include site preparation, foundations, structural frames, roofing, external walls, windows, internal partitions and finishes. Contractors may also arrange or undertake plumbing, electrical, heating, ventilation, fire-safety and drainage work, either through their own teams or subcontractors. Some provide project management, cost planning, construction scheduling and coordination of building inspections, while others focus on particular stages of construction.