Each winter a spell of exceptional cold weather catches a lot of builders and householders napping, resulting in frozen water supplies, burst pipes and consequent building damage. This is the time to think about taking steps to prevent a repeat performance. The cost of repairing the damage caused by water from a burst pipe is out of all proportion to the cost of installing protection. This Good Building Guide looks at how to prevent freezing of water supplies, inside and out, with advice for both new and existing buildings.