Once you know your zoning and what can be built on your property, then you need to determine the level of planning review required for your project.
If you are building a minor addition to your home (adding less than 50% new area), then you may be able to submit your plans directly to the Building Department. Any minor addition of floor area will be routed to the Planning Department for zoning clearance.
If you are building a new house or increasing the size of your existing house by more than 50%, your project will require design review approval. There are other circumstances where your project might need design review approval.