Glass supplies in Christchurch are low after many glaziers had their stock smashed in Saturday's earthquake.
Window Association member Bryn Thomson, says most glass businesses in Christchurch have lost 50% - 90% of their stock.
Up to 80% of all glass used in the South Island is supplied by two companies in Christchurch - Viridian and Metro GlassTech.
Metro GlassTech chief executive Andrew Bailey says up to half of its $2 million worth of stock was smashed and the factory had to close briefly.
But Mr Bailey says the shortage should not last more than a few days because fresh supplies are arriving by road and sea and the factory is already cutting glass again.