There is no quick answer to this frequently asked question. The fee is usually structured in one of three ways: as a reflection of the number of hours needed to do the work; as a percentage of the total construction cost; or as a fixed fee with a stipulated sum.
Sometimes, an architect will propose to bill the initial stages of a project on an hourly basis, as it is difficult to determine how much work he will have to do to reach agreement on your requirements, and produce an initial scheme, which meets your objectives.
The hourly rate and percentage of construction cost will vary according to the nature of the project and the services you require your architect to provide.
For an answer specific to your project, arrange an appointment with an architect who will determine the scope of your project and will provide you with a written proposal.