In short, as early as possible.
As soon as you have project in mind, whether it be a new house, extension, development or commercial project, it will pay dividends to make contact with an architect as early as possible in the process.
An initial chat with an architect, even prior to appointment, will allow your own ideas to develop. You will also receive good advice on what will be involved in the course of your project such as whether planning and building warrants are required and an idea of what hurdles may need to be overcome both before and during construction.
ultimately maximise the potential of your development
The value of an architect is important at all stages of a project. Advice in the initiation stages, knowledgeable design and technical input, co-ordination of other professionals and an independent third party overseeing construction works and financial aspects of a contract will all prove valuable input from your architect.
Importantly, this prevents mistakes being made, falling foul of relevant legislation, an efficient approach to problem solving and will ultimately maximise the potential of your development.