A Sketch is Not a Blueprint.

When I plan a work I want a free-form vehicle to take the story from conflict to resolution. What I do not want is a rigid structure that micromanages my prose. While the romantic image of a novelist just sitting down at a typewriter and tapping out the Great American Novel is amusing indeed, there does, if the planning is done correctly, come such a moment when one simply 'Writes'. That is the objective of proper planning.
To get to that point of 'Writing', I begin by sketching paragraph topics, scene by scene, with a sense of chapter endings and beginnings. I then develop these topics into full paragraphs and those paragraphs into pages of content draft. By doing it this way, I maximize my creativity in the moment while maintaining my narrative structure, while making sense. This content draft is the underlying structure of the book which I then transform, by 'Writing', into a rough draft of some literary merit, of some style.
A novel is a complex and difficult form but it does reduce at some point of experience to a magic mix of what the author said and how they said it. Sketching a work allows that magic to happen. Blueprinting it denies such possibility.