Mould (or fungus) on exterior brick walls is a growing concern in the USA. According to the National Association of Home Builders, the insurance industry paid out more than $1 billion in claims to remedy mould problems in 2001. Consequently, the insurance companies are cooperating with legislators to develop guidelines on mould removal from brick veneer. The primary reason for mould growth is poor workmanship and a failure to follow Building Industry Association guidelines which recommend a minimum two inch air space to allow for water drainage. All flashing should also be accompanied by weep holes.