Building of civil defense shelters in the rock is determined by defense aspects. The increasing destructive power and diversity of weapons demand protection of command, communication, alarm and computer centers, civil defense formations, stores, welfare institutions as well as civilians in the most menaced areas into rock constructions. The protection level in Finland is determined, in the first place, by conventional weapons. As to nuclear weapons, the pressure and vibration as well as the radioactive post radiation effects shall be taken into consideration to a certain degree. Electromagnetic puls and effects of chemical weapons shall be considered in important command centers. In regard to security politics of the country it is indispensable that the most important political administrative bodies like government, parliament, central bureaus, county governments, municipal direction etc. are sheltered in rock spaces. In view of information activity the important broadcasting and TV-studios are sheltered also in the rock. The same concerns safety storing of the most important raw-materials and first of all of oil. Nut only the defense aspects but also practical and economical facts support rock construction for purposes of peacetime. As an example can be mentioned the metro of Helsinki, Research Laboratories of Helsinki University of Technology, Paijanne Tunnel and subsurface parking lots in districts lacking sufficient space above ground. All abovementioned facilities can be used also for civil defense purposes. The latest development of building methods and of machines and equipment needed therein makes the rock construction still more advantageous. In addition this kind of construction saves expensive work of outside surfaces requiring continuous maintenance. To maintain comfort of the personnel working in subsurface spaces there are many means available today. It is clear that so called constructional civil defense, fur being successful, requires legislation, standards, type approval and strict control. In addition continuous maintenance of equipment is to be organized and costs involved financed.
According to utilization, the shelters can be divided into house shelters, collective shelters, public shelters and equipment shelters. The house shelter is built for a certain house, mostly of steel concrete. The collective shelter can be common for two or more houses situating on the same lot, made mostly of steel concrete. The collective shelter can also be a centralized shelter replacing house shelters of a larger residential area. This is often a rock shelter. The equipment shelters are among other things built for protection of various Kinds of technical Instruments. In construction of rock shelters there have been lately considerable alterations which have lowered the costs. According to new regulations, if the floor and wall space per sheltered person is sufficient, cooling of rock shelter, removing the carbon dioxide and adding of oxygen can be omitted. In other words, if the amount of cooling surfaces limited to the protection space is less than 2,4 square meters per sheltered person, the shelter is to be equipped with cooling devices. If the cooling surfaces are less than 1,2 square meters per sheltered person, the cooling devices are to be protected also from electromagnetic puls.