The company Kostak, komunalno in gradbeno podjetje, d. d., has been in operation for over 70 years and along with its ten subsidiaries forms the Kostak Group. We are one of the largest employers in the Posavlje region and the fastest growing business groups in Slovenia. We currently employ 700 workers, including 2 PhD and 6 MSc holders, as well as 57 engineers.

The main commercial activity of our company is construction. We successfully manage the most demanding infrastructural projects in the field of construction of industrial, energy, commercial and residential facilities. We build and maintain municipal infrastructure, regional and local roads, we perform all forms of ground works and excavations, and restorations of landslides. As the leading construction company in the Lower Sava Region, we have earned a reputation as a reliable and innovative business.

Within the last ten years, we have also become the leading company on the Slovenian market in the field of waste treatment and production of alternative fuels. Furthermore, we internationally share the knowledge obtained in the area of municipal and industrial waste management.

The Kostak Group operates in accordance with ISO 9001, ISO 1400, ISO 50001 and OHSAS 18001 standards, which ensures that each project meets the highest quality and safety criteria.

We invest in continuous improvements and employee training, as we strive to develop an internal and external business environment based on trust, cooperation, integration and interconnection with customers, employees, owners and the broader environment.



For over 60 years construction has been Kostak’s leading market service. The services we provide include architectural design, engineering and construction and reconstruction of:

  • Industrial infrastructure: production, storage and factory facilities
  • Power providing infrastructure: hydro-, thermal- and nuclear power facilities
  • Public infrastructure and wastewater treatment plants
  • Complete street and road infrastructure including roads, tunnels, bridges, intersections, interchanges, roundabouts and traffic circles, pedestrian infrastructure
  • Residential buildings – houses and apartment blocks
  • Commercial, educational, government, historic, religious and other types of buildings
  • Sport and recreation facilities

Waste management

Kostak has established its own efficient waste management system by building its own sorting plant for mixed municipal solid waste, a composting plant and a production line for Solid Refined Fuel. This system not only enables alternative use of more than 95 % of all the collected waste but is also environmentally friendly by leaving less than 5 % of waste to be disposed of. The waste managing infrastructure enables separation and preparation for further use in production as raw materials.


Kostak provides a variety of services for individual, communal and industrial purposes. We are qualified to provide maintenance for the most demanding clients such as Nuclear Power Plant Krško where services are being provided in Radiologically Controlled Area.

Our maintenance services include: administration, cleaning and decontamination in Radiologically Controlled Area, services in food distribution plant, cleaning in business premises, cleaning in production area, internal sewage and water supply maintenance as well as maintenance of buildings and surrounding areas.

Our Mission

Our mission is to provide best services for our clients at affordable prices. Our goal is to increase the quality of life for all our citizens.

Our Vision

Our vision is to develop an internal and external environment that will reflect our culture of trust, cooperation, integration and openness to our customers, employees, owners and society.

Our Values

Our corporate values are:

  • Tradition
  • Trust
  • Business excellence
  • Fairness
  • Respect for moral and ethical values
  • Respect for an individual
  • Creativity and constant learning
  • Corporate social responsibility
  • Environmental protection
  • Cooperating with society
  • Occupational health and safety

Quality standards

Kostak has established an integrated management system which consists of:

  • Quality management system ISO 9001
  • Environmental management system ISO 14001
  • Occupational health and safety system OHSAS 18001
  • Energy management system ISO 50001
  • Food safety system HACCP
  • Information security management ISO/IEC 27001
  • Quality Assurance Criteria for Nuclear Power Plants and Fuel Reprocessing Plants 10CFR50, app. B

Corporate social responsibility

Our employees are key element to our success. We invest in developing our own professionals, we support our employees in obtaining a higher educational level and provide various possibilities for personal growth, education and professional development. We build a culture of trust, respect, team effort and responsible, efficient work.

We grow with our local community by supporting various sport and cultural activities and by donating to those in need. We also pass our knowledge and experiences on to younger generations by organizing and participating in events for raising awareness on environmental issues.

We have taken significant measures to ensure our impact on the world is sustainable and responsible. It is our commitment to the people and the environment.

Family Friendly Enterprise Certificate

For a significant development in human resources Kostak was the first public utility in Slovenia to receive a full Family Friendly Enterprise Certificate, which was issued by Slovenian Ministry of Labour, Family, Social Affairs and Equal Opportunities in 2012.

Corporate Social Responsible Certificate

In 2016 Kostak received a Corporate Social Responsible Certificate, issued by the Ekvilib Institute. CSR Certificate is an analytical and advisory procedure, based on socially responsible management of company or organization.