Abstract
The three scale about big, middle and small office model building was supposed to make use of the calculation of vepair cost. Useful life of whole building was 60 years, the repair cost was calculated by the repair cycle and renew cycle of building component. The annual whole building cost (=initial cost+running cost) made clear that long useful life made cost down. Before useful life was 40 years or so, middle scale office building was the most down ward cost.
