The simple answer
Home addition plans usually need to show the existing home, proposed new area, site placement, structural tie-ins, exterior changes, utility coordination, and construction notes needed for jurisdiction review.
What addition plans usually need to show
Exact requirements vary by property and jurisdiction, but additions typically need more coordination than simple interior remodels because the building footprint and exterior condition are changing.
Site placement
The plans should show where the addition sits on the lot, how it relates to property lines and setbacks, and how it affects access, drainage, utilities, and existing structures.
Existing-to-proposed layout
Addition plans need to show what exists now and what is changing, including room connections, circulation, openings, and how new space ties into the existing home.
Structure and roof tie-ins
Foundations, roof forms, wall framing, openings, headers, beams, and engineering coordination can be important when new construction connects to an existing home.
Utilities and systems
Plumbing, HVAC, electrical, water heaters, panels, and mechanical routing may need to be considered depending on the location and use of the new space.
Helpful information to gather first
The addition design depends on the existing house and the site. Accurate starting information helps reduce redesign and plan review corrections.
- Property address and jurisdiction
- Approximate size and intended use of the addition
- Photos of the existing home and affected exterior areas
- Old plans, survey, or site information if available
- Known HOA, floodplain, easement, septic, or utility constraints
- Whether walls, roof, foundation, plumbing, HVAC, or electrical systems are affected
Existing plans may not be enough
If the existing home has changed since the original plans were drawn, as-built drawings may help establish a reliable base.
Site constraints can shape the addition
Setbacks, easements, lot coverage, utilities, drainage, and access can affect where the addition can go and how it connects to the existing home.
Related remodel planning
For a comparison of project types, read remodel vs addition permit process in Arizona. For general remodel permit questions, see whether you need plans for a remodel.
Planning a home addition in Arizona?
Residential Design can help document existing conditions, develop addition layouts, and prepare permit-ready plans for Arizona home additions.