There are plenty of moisture damages in building stock in Finland in need of repair. The damages are caused by the errors in planning, moisture control during construction and the errors in the use of buildings and insufficient maintenance. Some of the damages are due to the wear of materials. Errors can be avoided by good designing, thorough construction and the right use of buildings. The purpose of this Bachelor’s thesis was to study moisture control during construction. The thesis was commissioned by Vertia Oy which conducts moisture and air leakage tests of buildings and organizes training in the field. The aim was to find out the measures needed to prevent moisture damages during building. Moisture contaminates indoor air and causes health hazards. Moisture penetrates buildings internally and externally. Moisture must even be brought into structures to make construction possible. How-ever, all moisture must also be removed to proceed with construction. An-other aim was to collect material for drawing up a manual of moisture control on low-rise building sites. Publications in the field including regulations, good practices, instructions and statistics were studied. In addition, experts in the field were inter-viewed. The result of the thesis show that moisture damages during building site can be prevented in simply ways. They are based on careful advance planning and construction work. Energy efficiency regulations will set challenges on the tightness of buildings. If the tightness is poor it will also cause moisture damages and deterioration of indoor air. The tightness of buildings is as important as dry building.