Vancouver, British Columbia, Canada, 30 January 2008 -- Ainsworth Lumber Co. Ltd. today announced that it will extend for one week the previously announced maintenance closure at its oriented strand board (OSB) mill in Grande Prairie, Alberta, until 10 February due to reduced customer demand. Ainsworth had earlier announced a maintenance closure from 28 January to 03 February. The Grande Prairie mill has an annual production capacity of approximately 665 million square feet (3/8-inch basis).