Professional and trade organisations often maintain registers of members that can be extremely useful if you are trying to locate a professional advisor or building contractor in your area. Many of these registers are available on line, and may give additional information about members' experience with or formal accreditation for work on historic buildings.
The websites of these organisations can also be valuable sources of information about materials and their characteristics, current practice, sources of supply and industry accreditation schemes.
When using the resources provided by these organisations, it is important to remember, however, that most of the groups are not specifically concerned with historic buildings. The appearance of an advisor or contractor on a register does not necessarily indicate any expertise in dealing with the problems posed by historic buildings. The sites may also encourage the use of modern materials and techniques that may be unsuitable, and perhaps even harmful, when applied to historic buildings.