Roof Plan
Show existing and proposed slopes, ridges, valleys, eaves, drainage direction, penetrations, and ventilation relationships.
What Drawings Do You Need for a Home Addition?
A home addition drawing package has to explain two buildings at once: the house that exists and the work that will change it. The critical sheets are the ones that make the site fit, demolition, structural tie-in, roof, and proposed layout agree.
The Short Answer: A Typical Home Addition Drawing List
| Drawing or document | What it answers | Addition-specific issue |
|---|---|---|
| Cover and code sheet | What is being built and which rules organize the set? | Areas, scope, occupancy, construction type, and sheet index |
| Site or plot plan | Does the addition fit the property? | Setbacks, coverage, easements, utilities, access, grade, and drainage |
| Existing floor plan | What is there now? | Full affected area and the walls, openings, fixtures, and levels involved |
| Demolition plan | What is removed or altered? | Exterior wall opening, roof removal, foundations, and systems affected |
| Proposed floor plan | What will the finished layout be? | New rooms, dimensions, egress, circulation, openings, and tie-in |
| Foundation and framing | How is the addition supported? | New-to-existing connections, loads, bearing, and lateral path |
| Roof plan | How do old and new roofs meet? | Slopes, valleys, drainage, ventilation, and penetrations |
| Exterior elevations | How does the addition change the exterior? | Height, grade, openings, materials, roof, and affected facades |
| Building sections and details | How do assemblies connect vertically? | Foundation, floor, wall, roof, flashing, insulation, stairs, and transitions |
| Supporting documents | What belongs to outside reviews or professionals? | Survey, structural calculations, energy, flood, grading, septic, HOA, or trade work |
This is a scoping map, not a universal submittal checklist. The authority having jurisdiction decides the final package.
Why Addition Plans Need More Existing-Condition Information
A new detached building can be documented around a new design and a surveyed site. An addition must also explain the existing structure it touches. That can include floor and roof framing direction, foundation type, wall thickness, window and door locations, finished-floor elevations, ceiling changes, utilities, and visible signs of prior alterations.
Portland's official residential addition guidance requires existing and proposed work to be distinguished and says the whole floor layout must be shown even when work affects only part of the building. The City of Irvine's addition page calls for existing and proposed layouts, roof information, elevations, sections through the addition and existing structure, and applicable details.
If reliable base plans do not exist, begin with how to find plans for an existing house and decide whether the project needs measured as-built drawings.
1. The Site Plan Proves the Addition Fits the Lot
The site plan commonly shows property lines, existing and proposed footprints, dimensions, setbacks, easements, streets, driveways, accessory structures, utilities, north direction, and project-specific grade or drainage information. The information source matters. Parcel maps, GIS, old plans, and surveys are not interchangeable.
The City of Vancouver, Washington lists the site plan first in its residential addition checklist. Irvine may require a licensed survey for an addition that extends into a side yard or approaches a required setback. The City of Alameda includes plot and grading plans for additions when applicable.
Resolve the property base before perfecting an interior layout. A room that does not fit the buildable envelope is not a design solution.
2. Existing, Demolition, and Proposed Plans Must Agree
These plans tell one sequence. The existing plan establishes the starting condition. The demolition plan identifies what changes. The proposed plan shows the finished arrangement. They should use the same orientation, scale, reference points, room names, and graphic legend.
- Show the full affected level and enough adjacent context to understand circulation and structure
- Separate walls to remain, walls removed, and new walls with a clear legend
- Dimension the addition, openings, rooms, and controlling relationships
- Label room uses, doors, windows, stairs, fixtures, and required life-safety information
- Track exterior openings across plans, elevations, and structural work
- Identify floor-height changes and accessibility consequences
- Coordinate the plan with roof, foundation, and site geometry
A demolition note cannot replace an accurate existing base. If the field condition is uncertain, mark it for verification instead of burying the assumption.
3. Foundation and Structural Drawings Explain the Tie-In
An addition introduces new loads and a connection to an existing building. The plan package may need foundation layout and details, floor and roof framing, beams, headers, posts, shear or braced walls, connections, and calculations. Responsibility for that work depends on law, jurisdiction, and scope.
Vancouver's checklist calls for foundation details, floor and roof framing, and wall-bracing information. The City of New Braunfels' residential addition checklist identifies site, foundation, framing, and Texas engineering requirements for specific conditions. These examples show why "addition plans" should never be quoted without a consultant map.
Apex can draft and coordinate the architectural set while identifying sheets or calculations that must be prepared, reviewed, or sealed by the responsible licensed professional. Read when residential plans may need an engineer stamp before assuming every sheet has the same author.
4. Roof Plans, Elevations, and Sections Resolve the Hard Parts
Addition problems often concentrate at the roof and vertical transitions. A plan may look simple from above while creating a valley against an existing wall, a low head-height zone, a drainage conflict, a step between floor levels, or a difficult foundation transition.
Elevations
Show affected sides, grade, heights, openings, roof form, exterior materials, and how new work meets the house.
Sections
Cut through the connection to explain foundations, floors, walls, roof, insulation, flashing, ceiling heights, and stairs.
Toronto's current small residential addition guide separately lists roof plans, elevations, and sections with the information expected on each. The exact code framework differs in the United States, but the drawing logic is the same: each view resolves a different class of question.
5. Supporting Documents Can Change the Architectural Design
Energy compliance, structural calculations, a current survey, drainage or grading, floodplain information, septic approval, wildfire requirements, utility coordination, product approvals, truss documents, historic review, and HOA approval are not decorative attachments. They can change wall thickness, openings, roof form, finished-floor elevation, equipment space, and buildable area.
San Diego's residential addition and remodel bulletin identifies project documents and existing-versus-proposed information for that jurisdiction. Every focus market has its own sequence. Use the Apex residential permit requirements index to reach official starting pages, then confirm the address-specific checklist before final issue.
Build the Drawing Scope in This Order
- Confirm the authority. Identify the city or county that will review the addition.
- Pull the current checklist. Record required sheets, file standards, forms, and prior approvals.
- Establish the property base. Review the survey, parcel, easements, setbacks, utilities, grade, and existing structures.
- Document existing conditions. Verify the affected building geometry and tie-in zones.
- Freeze the project program. Define room uses, target size, must-haves, budget constraints, and design decisions.
- Assign outside responsibilities. Map structural, survey, energy, civil, flood, septic, HOA, and trade work.
- Coordinate every view. Cross-check site, floor, roof, elevation, section, detail, and consultant information.
- Prepare the upload package. Follow the jurisdiction's current naming, sheet, seal, and portal rules.
This order prevents a polished floor plan from outrunning the site and technical facts that determine whether it can be approved and built.
What to Send for an Addition Drawing Quote
- Exact address, parcel number, and reviewing jurisdiction
- Current survey or the best property document available
- Original plans, alteration plans, and permit history
- Wide photos of all exterior sides and every affected room
- A sketch and plain-language description of the proposed addition
- Approximate size, room uses, and preferred roof or exterior direction
- Known structural, drainage, utility, septic, flood, or HOA constraints
- Desired deliverables: feasibility, permit, builder pricing, or construction issue
- Target dates and any fixed contractor or permit milestones
Use the drafting quote intake checklist to make provider proposals easier to compare.
Related Home Addition Resources
Read what goes in a residential permit set, signs an addition needs a full permit set, addition versus new construction, or explore permit-ready plan sets.
Home Addition Drawing FAQ
What drawings are usually required for a home addition permit?
A typical addition package includes a cover sheet, site plan, existing and proposed floor plans, demolition information, roof plan, exterior elevations, building sections, and construction details. Structural, energy, grading, trade, survey, or other documents may also be required.
Do addition plans need to show the existing house?
Yes, to the extent needed to understand the work and verify the tie-in. Many jurisdictions require the affected floor or the whole floor layout, clear existing-versus-proposed graphics, and exterior views that show how the addition relates to the house.
Do I need an architect or engineer for a home addition?
Requirements depend on state law, local rules, project size, structural scope, and building type. Drafting, architectural practice, engineering, surveying, energy compliance, and permit submission are separate responsibilities that should be assigned before the plan set is priced.
Can a contractor sketch be used for the permit?
A sketch is a useful scope input, but a permit office may require scaled, dimensioned, coordinated drawings plus project-specific technical information. Check the current local checklist before assuming a sketch is enough.
Does every home addition need a site plan?
A site plan is common because an addition changes the building footprint and can affect setbacks, lot coverage, access, grading, drainage, utilities, and easements. The required source information and level of detail vary by jurisdiction.
What should I gather before ordering addition plans?
Start with the exact address and jurisdiction, a current survey if available, original or prior plans, permit history, photos, a project description, target size, budget constraints, and the permit office's current addition checklist.
Planning a Home Addition?
Send the address, survey, existing plans, photos, and a plain-language description of the addition. Apex will map the drawing package and outside consultant needs before quoting.
Prefer to talk it through? Call (435) 990-3556.