Overtime wages at double rate govern extended working hours, with quarterly limits and special exceptions for specified operations. Overtime wages are payable at twice the ordinary rate where a daily wager works more than eight hours in a day or a worker other than a daily wager works more than forty-eight hours in a week, and such overtime wages are to be paid at the end of each wage period. For calculating overtime, a fraction of an hour from fifteen to thirty minutes is treated as thirty minutes, and anything beyond thirty minutes is counted as a full hour. The prescribed hours of work may be exceeded in specified dock, mine, building and other construction work, subject to a ceiling of one hundred forty-four hours in a quarter of a year.