We should consider climatic factors influencing construction works in order to estimate construction time correctly. This study is to analyze climate elements affecting construction duration and to calculate non-working days far Inchoen territorial region. Through surveying literatures and examining several existing criteria we suggest a Proper criteria for each climate elements which would be used for estimating non-working days. The criteria is made on the raw climate data of Meteorological Administration during the last 30 years(1974-2003) far Incheon region. In case of rainfall, it is estimated as non-working days when daily precipitation is expected more than 10mm, its number of days for Incheon is 29 days. In case of low temperature, the number of non-working days for the concrete works(its criteria be below $4^{circ}C$ average) and the finishing works(below $0^{circ}C$ average) is 97 days, 52 days, respectively. In case of high temperature, it is three days when daily highest temperature is expected going over $32^{circ}C$