Starting times must comply with local government by-laws which dictate the hours within which on-site work can take place. You should consult the building department of your local authority for the relevant requirements. Compliance with these by-laws is a condition on which the building licence is issued to the builder.
Once you have discovered the allowable hours, if there are continual breaches by tradespersons and you feel uncomfortable about approaching them directly about their starting time or noise level, the next step is to consult the builder. The builder’s contact details are listed on the building signage on the site. As the builder is responsible for the site, he or she can order the on-site contractors to comply with local by-laws. Most builders appreciate the value of “word of mouth” reputation and would be anxious to maintain cordial relations with neighbours who may be their future customers.
Depending on the noise level generated, say from machinery, there may be recourse through Worksafe. While some noise intrusion is unavoidable occupational health and safety requirements restrict on-site noise to a certain decibel level. The Environmental Protection Authority also issues guidelines about Noise Control on Building Sites.
Sometimes the best approach is simply to politely ask the subcontractors to modify their on-site behaviour. This can often achieve the deserved result without the need to resort to more legalistic approaches to the issues. If the personal approach does not work, you then have these other avenues available to you.