How much do ADU plans cost in 2026? For most standard detached or attached accessory dwelling units in the United States, complete permit-ready adu plans cost between $1,200 and $2,500 when prepared by a professional CAD drafting service, compared to $8,000 to $18,000+ when hiring a full-service architectural firm. On a square-foot basis, professional architectural drafting averages $1.00 to $2.50 per square foot, whereas licensed architects charge $8.00 to $18.00 per square foot (or 8% to 15% of total projected construction cost).
While generic stock plans sell online for as little as $800 to $1,500, those downloadable templates lack site-specific plot plans, utility tie-in routes, local foundation engineering, and regional energy documentation. To obtain a building permit, your municipal building department requires a site-adapted, code-compliant construction document set that satisfies local zoning setbacks and structural building codes.
Whether you are a general contractor bidding a client build or an owner-builder planning a backyard rental, here is an itemized breakdown of ADU plan costs by square footage, drawing methods, and required technical deliverables.
Quick Cost Overview: ADU Plans by Square Footage
| ADU Size & Configuration | Square Footage | CAD Drafting Cost (ArchWorkPro) | Traditional Architect Fee (8% - 15%) | Typical Turnaround | Municipal Plan Check Readiness |
|---|---|---|---|---|---|
| Studio ADU (Compact Box) | 350 to 450 sq ft | $1,200 flat (project minimum) | $6,000 to $10,000 | 5 to 7 business days | Submittal-ready architectural set |
| 1-Bedroom / 1-Bath ADU | 500 to 650 sq ft | $1,200 flat ($1/sq ft floor) | $8,000 to $13,500 | 7 to 10 business days | Submittal-ready architectural set |
| 2-Bedroom / 1-Bath ADU | 700 to 850 sq ft | $1,200 flat ($1/sq ft floor) | $10,000 to $16,000 | 7 to 10 business days | Submittal-ready architectural set |
| 2-Bedroom / 2-Bath ADU | 900 to 1,000 sq ft | $1,200 flat ($1/sq ft floor) | $12,000 to $18,500 | 10 to 12 business days | Submittal-ready architectural set |
| Large 2-Story ADU / Over Garage | 1,050 to 1,200 sq ft | $1,200 flat ($1/sq ft floor) | $15,000 to $24,000+ | 10 to 15 business days | Submittal-ready architectural set |
The 3 Ways to Get ADU Plans (And What Each Really Costs)
Homeowners and contractors generally choose among three distinct paths to obtain ADU blueprints. Each route involves different trade-offs between upfront price, speed, and real submittal readiness.
ADU PLAN DELIVERY METHODS: INITIAL PRICE VS. REAL SUBMITTAL COST
Method 1: Online Stock Catalog Plan
Initial: $1,000 ----> Real Submittal Cost: $4,500 - $7,000 (Site plan + engineer + energy)
Method 2: Full-Service Licensed Architect
Initial Retainer: $3,500 ----> Real Submittal Cost: $10,000 - $20,000+ (8% - 15% of build)
Method 3: Fixed-Rate CAD Drafting (ArchWorkPro)
Initial Quote: $1,200 ----> Real Submittal Cost: $1,200 Flat ($1/sq ft, free corrections)
1. Online Pre-Drawn Stock Plans ($800 to $2,000 Upfront, $4,500 to $7,000 Real Cost)
Many websites sell pre-designed ADU floor plans in downloadable PDF format.
- The Reality: Building departments review buildings on specific parcels of land, not abstract ideas. A stock plan does not know where your sewer line runs, whether your lot slopes, what wind exposure category applies, or how close your walls sit to property lines.
- The Hidden Expense: To submit a stock plan, you must hire a local CAD drafter to draw your custom plot plan ($600 to $1,500), pay a structural engineer to recalculate the foundation for local soil and seismic forces ($2,000 to $3,500), and pay an energy consultant for Title 24 or REScheck forms ($350 to $600). Your "$900 stock plan" quickly becomes a $5,000 expense.
- Best For: Homeowners browsing layout inspiration or contractors who have in-house draftsmen capable of modifying CAD files.
2. Full-Service Licensed Architectural Firm ($8,000 to $20,000+)
Traditional architecture practices cater primarily to custom luxury homes and commercial projects.
- The Reality: Architects charge either a percentage of construction cost (typically 8% to 15%), an hourly rate ($125 to $250+ per hour), or a steep flat design retainer. On a $150,000 detached ADU build, a 10% architectural fee equals $15,000.
- The Drawback: Architects provide extensive schematic design meetings, hand-drawn mood boards, and finish selections. For a straightforward 600 to 800 square foot detached ADU, this process is excessively slow (8 to 16 weeks) and consumes a disproportionate share of your total construction budget.
- Best For: High-end custom architectural showpieces on complex, multi-tiered hillside parcels with unrestricted budgets.
3. Professional Fixed-Rate CAD Drafting (ArchWorkPro: $1/sq ft, $1,200 Minimum)
ArchWorkPro bridges the gap between incomplete stock drawings and overpriced architectural firms.
- The Reality: We provide complete, customized 2D CAD permit sets at a published flat rate of $1 per square foot of drawn area, with a $1,200 project minimum.
- For any single-story ADU up to 1,200 square feet, your architectural permit drawing package costs $1,200 flat.
- Fast Written Quotes: Send us a rough layout sketch or project dimensions, and you will receive a firm written quote within 2 working hours.
- Rapid Turnaround: Drawings delivered in days, not months.
- Unlimited Free Revisions: All city plan check correction rounds within the approved scope are handled at zero extra cost.
To get an exact quote on your project, submit your details at /get-started or view our complete rate card at /pricing.
What Must Be in a Complete ADU Permit Drawing Set?
Municipal plan examiners do not approve conceptual layouts. The building division enforces the International Residential Code (IRC), the National Electrical Code (NEC), and state building standards.
To pass plan check, your ADU drawing package must include the following coordinated sheets:
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| ANATOMY OF A COMPLETE ADU PERMIT DRAWING SET |
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| SHEET 1: COVER SHEET & GENERAL CODE NOTES (G-1) |
| - Legal project address, Assessor Parcel Number (APN), zoning district |
| - Applicable building code editions and local fire hazard classification |
| - Scope of work summary, sheet index, and building area calculations |
+-----------------------------------------------------------------------------------+
| SHEET 2: PLOT / SITE PLAN (SP-1) |
| - Scaled property boundaries showing street frontage and rear/side property lines |
| - Primary dwelling footprint and proposed ADU footprint with exact setbacks |
| - Lot coverage calculations, Floor Area Ratio (FAR), and open space percentages |
| - Utility trenching paths (sewer lateral, water service, electric meter, gas) |
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| SHEET 3: DIMENSIONED ARCHITECTURAL FLOOR PLAN (A-1) |
| - Complete room layout with interior wall dimensions, door swings, and hallways |
| - Complete kitchen counter, sink, range, and refrigerator locations |
| - Bathroom layout showing clearances for toilet, vanity, and shower/tub |
| - Door and window schedules detailing rough openings, egress sizes, and U-factors |
| - Hardwired smoke and carbon monoxide detector locations |
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| SHEET 4: EXTERIOR ELEVATIONS (A-2) |
| - Four exterior views (Front, Rear, Left, Right) showing finished grade elevations|
| - Overall building height, wall plate heights, and roof pitch dimensions |
| - Exterior wall finishes (stucco, lap siding, board-and-batten) and trim details |
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| SHEET 5: BUILDING CROSS-SECTIONS & ROOF PLAN (A-3) |
| - Vertical cross-section detailing slab thickness, wall studs, and ceiling height |
| - Roof drainage slopes, eaves, overhangs, and ventilation calculations |
| - Fire-rated wall assembly details for walls located within 5 feet of lot lines |
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| SHEET 6: STRUCTURAL FOUNDATION & FRAMING PLANS (S-1) |
| - Concrete slab-on-grade or raised perimeter stem wall footing with rebar spacing |
| - Floor, ceiling, and roof framing plans specifying lumber grades and spans |
| - Shear wall schedules, hold-downs, and nailing patterns for lateral wind/seismic |
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| SHEET 7: MECHANICAL, ELECTRICAL & PLUMBING SCHEMATICS (MEP-1) |
| - Lighting plan, receptacle layout, and dedicated appliance circuits (AFCI/GFCI) |
| - Electrical subpanel sizing (typically 100A) and service load calculations |
| - Plumbing single-line diagram with drain-waste-vent (DWV) and water pipe sizing |
| - Ductless mini-split HVAC location and ventilation fan CFM ratings |
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To see our dedicated permit package options, explore our permit sets overview or read our specialized guide on ADU design plans.
What Costs Extra? (Engineering Stamps, Energy Reports, City Fees)
When budgeting your total pre-construction soft costs, differentiate between drafting fees (the drawings), engineering consultant fees, and government municipal fees.
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| PRE-CONSTRUCTION ADU SOFT COSTS BREAKDOWN |
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| 1. ARCHITECTURAL CAD DRAFTING (ArchWorkPro) | $1,200 Flat Floor Rate |
| 2. STRUCTURAL ENGINEERING CALCULATIONS & PE STAMP | $1,500 - $3,500 |
| 3. TITLE 24 / RESCHECK ENERGY COMPLIANCE REPORT | $350 - $650 |
| 4. PROPERTY BOUNDARY / TOPOGRAPHIC SURVEY (if required) | $1,800 - $3,500 |
| 5. CITY PLAN CHECK & BUILDING PERMIT FEES | $1,500 - $5,000+ |
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| TOTAL TYPICAL PRE-CONSTRUCTION BUDGET | $6,350 - $13,850 |
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1. Structural Engineering Calculations and PE/SE Stamp ($1,500 to $3,500)
Every new detached or attached ADU requires structural engineering to prove the building will resist gravity, wind, and earthquake loads.
- A licensed Professional Engineer (PE) or Structural Engineer (SE) calculates footing depth, structural headers over patio doors, hold-downs, and shear wall nailing.
- ArchWorkPro is a professional architectural drafting service. Where a jurisdiction requires a licensed engineer or architect stamp, we coordinate review and stamping with licensed state professionals as a separate line item.
2. Title 24 or REScheck Energy Compliance ($350 to $650)
In states with strict energy codes (such as California Title 24, Washington, or New York), building departments require a certified energy compliance report. A certified energy consultant models the ADU envelope, insulation values, window performance (U-factor and SHGC), water heating, and HVAC efficiency to generate official compliance certificates (such as the CF1R form in California).
3. Boundary or Topographic Surveys ($1,800 to $3,500)
On a flat, suburban lot with established fence lines and recorded boundary pins, your drafter can usually prepare a site plan using parcel maps and satellite data. However, if your lot has a noticeable slope (more than 4 to 5 feet of elevation change across the building footprint) or you are building right against minimum 4-foot setback lines, cities will require a boundary survey prepared by a licensed Professional Land Surveyor (PLS).
4. Municipal Plan Check and Building Permit Fees ($1,500 to $5,000+)
City fees are government taxes paid directly by the property owner to the local building department:
- Plan Check Fee: $600 to $2,000 (paid at the time of initial submittal).
- Building Permit Issuance Fee: $1,000 to $3,000 (paid when the permit is ready to be pulled).
- Impact Fees: Under state laws in California and Washington, ADUs under 750 square feet are statutorily exempt from school, park, and traffic impact fees. Units 750 square feet or larger may be assessed proportional impact fees.
Why Contractors and Owner-Builders Choose $1/Sq Ft Drafting
For professional remodelers, custom builders, and budget-conscious homeowners, paying an architect $15,000 for standard residential blueprints makes no economic sense.
PROPOSAL COMPARISON: 750 SQ FT DETACHED ADU
ArchWorkPro:
- 2D CAD Permit Drawing Set: $1,200
- Turnaround: Delivered in Days
- Plan Check Corrections: $0 (Included Free)
- Total Drawing Expense: $1,200
Traditional Architecture Practice:
- Design Fee (10% of $180k build): $18,000
- Turnaround: 10 to 14 Weeks
- Plan Check Correction Rounds: $175/hr additional
- Total Drawing Expense: $18,000+
By keeping design and drafting costs at a predictable $1 per square foot ($1,200 project minimum), you save between $6,000 and $16,000 on pre-construction soft costs, money that remains in your pocket or gets reinvested directly into higher-quality construction materials, luxury finishes, and energy-efficient appliances.
Frequently Asked Questions About ADU Plans Costs
How much do plans for a 750 sq ft ADU cost?
With ArchWorkPro, complete 2D CAD permit drawings for a 750-square-foot ADU cost $1,200 flat under our published $1 per square foot pricing (with our $1,200 project floor). A traditional architectural firm routinely charges between $8,000 and $15,000 for the same project.
Do I legally need an architect to draw my ADU plans?
No. In the majority of US states, single-family residential structures and accessory dwelling units are exempt from mandatory architect licensing laws under state residential design exemptions. A professional CAD drafting service can draft the complete architectural permit set. When local building departments require structural engineering calculations or foundation stamps, a licensed structural engineer provides the calculations, which ArchWorkPro coordinates as a separate line item.
Are pre-drawn stock plans accepted by city building departments?
Not out of the box. Stock plans do not include a custom site plan showing your property lines, setbacks, and utility trenching routes, nor do they include site-specific foundation engineering for local soil conditions. To submit a stock plan, you must hire a drafter and an engineer to adapt and localize the drawings, which typically costs an additional $3,000 to $5,000.
How long does it take to get ADU plans drawn?
With ArchWorkPro, custom 2D CAD permit drawings are completed and delivered in 1 to 2 weeks. Traditional architectural firms typically take 8 to 16 weeks to progress through schematic design and client consultations.
What information do I need to get an ADU plan quote?
All you need is your property address, your desired ADU square footage (or dimensions), and a simple sketch or list of desired rooms (e.g., 2 bedrooms, 1 bathroom, open kitchen). Send us your details, and we will return a written quote within 2 working hours.
Get a Fast, Fixed-Rate Quote on Your ADU Plans
Do not let high architectural retainers or multi-month design backlogs delay your ADU project.
ArchWorkPro delivers complete, permit-ready 2D CAD drawings at $1 per square foot of drawn area ($1,200 project minimum) with written quotes returned within 2 working hours.
- Full architectural floor plans, elevations, sections, and MEP schematics
- Rapid delivery in days
- Unlimited free revisions and plan check corrections included
