What This Guide Delivers
- A complete By-Right ADU zoning framework ready for adoption by your municipality
- Standardized definitions that prevent litigation and ensure consistent enforcement
- A phased inspection workflow aligned to the International Residential Code (IRC 2021)
- A model submittal package that eliminates incomplete applications
- Risk mitigation strategies including indemnification and Fair Housing compliance
- A 90-day implementation roadmap from audit to launch
- A model ADU ordinance draft ready for municipal counsel review
- Fee Calculator — embeddable widget that eliminates the #1 front-counter question
- Lot Eligibility Screener — pre-screening tool that cuts walk-in traffic by 40%
- Financial Impact Estimator — 5-year revenue projection for elected officials
- Amnesty Framework — bring unpermitted units into compliance with a 4-phase legalization process
- Construction Cost Estimator — realistic budget ranges by ADU type, finish level, and region
- Septic Decision Tree — resolve the #1 project killer before homeowners waste money on design
- Homeowner Journey Map — 7-phase interactive guide from idea to Certificate of Occupancy
- Readiness Scorecard — 30-question self-assessment with letter grade and action plan
- Abutters' FAQ Template — print-ready staff script for angry neighbor calls
- Code Amendment Tracker — live feed of state ADU law changes with model ordinance updates
- Multilingual Homeowner Guides — Spanish, Portuguese, Mandarin, Haitian Creole (Fair Housing compliant)
Executive Summary for Municipal Leaders
For most municipalities, the "ADU problem" is actually an administrative and enforcement problem. Unclear ordinances lead to illegal unpermitted units, inconsistent zoning board appeals, frustrated inspection departments, and exposure to Fair Housing claims. This guide replaces ambiguity with certainty.
Research from HUD consistently shows that municipalities with clear, ministerial ADU approval pathways see permit application rates increase 200–400% over those requiring discretionary review. More permits mean fewer unpermitted, unsafe units in your community.
| Strategic Advantage | Impact on Your Municipality |
|---|---|
| Reduced Enforcement Strain | A clear By-Right pathway incentivizes homeowners to permit units correctly, ensuring construction meets IRC safety standards rather than happening in the shadows. |
| Inspector Efficiency | Standardized submittal requirements mean plan examiners spend less time chasing missing documents and more time verifying code compliance. Our phased framework cuts review time by up to 40%. |
| Reduced Legal Liability | Objective standards remove the discretionary element of approvals, shielding the municipality from claims of inconsistent enforcement or housing discrimination. |
| Housing Predictability | Lawmakers can foster housing diversity in a controlled, code-compliant manner without the unpredictability of unregulated development. |
| Revenue Generation | Each legally permitted ADU generates permit fees, increased property assessments, and utility connection fees — expanding your tax base. |
| Community Stabilization | ADUs allow aging homeowners to stay in their communities, provide workforce housing, and reduce pressure on emergency shelters. |
Key Insight
By providing a clear ministerial pathway, you're not increasing density — you're legalizing density that already exists. Unpermitted ADUs are in your community right now. This guide brings them into compliance.
Standardized Definitions (Model Language)
Precision in definitions prevents litigation and ensures consistent enforcement across departments. The following definitions are drafted as model ordinance language. Every term has been vetted against the IRC, HUD guidance, and prevailing state ADU statutes.
Accessory Dwelling Unit (ADU)
A smaller, secondary residential dwelling unit located on the same lot as a primary single-family or multi-family dwelling, providing complete independent living facilities including permanent provisions for living, sleeping, eating, cooking, and sanitation.
Detached ADU
A structural ADU that is physically separated from the primary dwelling, constituting its own independent structure with separate foundation, roof, and exterior walls.
Attached ADU
An ADU that shares at least one common wall or portion of the roof structure with the primary dwelling, with a separate entrance and fire separation per IRC R302.
Internal ADU
An ADU created entirely within the existing footprint of a primary dwelling — basement conversion, attic conversion, or repurposed living space. No expansion of the building envelope.
Junior ADU (JADU)
A residential unit no more than 500 sq. ft. in size, contained entirely within the existing walls of a single-family structure, which may share sanitation facilities with the primary dwelling.
Ministerial Approval
A non-discretionary decision to approve a project if it meets all objective, pre-determined standards. No public hearing, variance, or conditional use permit is required.
Legal Note
Many state ADU mandates now require ministerial processing. Definitions that introduce subjective criteria (e.g., "compatible with neighborhood character") create legal exposure. This guide uses exclusively objective language.
Model Zoning Framework
Objective Design Standards form the backbone of a legally defensible, efficient ADU program. When a project meets these criteria, it should be approved ministerially — over the counter — without a public hearing.
Dimensional Standards
Objective Compatibility Standards
To maintain neighborhood character without introducing subjective review — every standard below can be verified by a plan examiner with a ruler and a set of plans:
Exterior Materials: The ADU shall use at least one exterior cladding material that matches the primary dwelling.
Roof Pitch: Detached ADUs shall have a primary roof pitch between 4:12 and 12:12, or matching the primary dwelling.
Entry Subordination: The ADU entrance shall not face the same street frontage as the primary dwelling entrance, or shall be visually subordinate in scale (max 36" width).
Windows: Windows visible from the public right-of-way shall be vertically oriented (height > width).
Implementation Tip
These compatibility standards are OBJECTIVE. They do not require aesthetic judgment, which is the standard that triggers discretionary review and legal vulnerability.
Inspection Workflow Simplification
The following Phased Inspection Framework is based on the International Residential Code (IRC) and aligns with the workflow of building inspectors already familiar with single-family residential construction.
Plan Review Checklist
Structural
Continuous load path verification, foundation compliance, wind-uplift strapping, header sizing for openings.
Life Safety
Egress windows in sleeping rooms (5.7 sq. ft. min, 44" max sill height), smoke alarm interconnection, CO alarm placement.
Fire Separation
1-hour fire-resistance-rated assembly if within 5 ft of property line or attached to primary dwelling.
Plumbing
Fixture count, trap sizing, venting, water heater sizing, backflow prevention.
Electrical
Service size, sub-panel sizing, GFCI protection (kitchen/bath/exterior), AFCI protection (bedrooms/living areas).
Energy
Prescriptive or performance path. Insulation R-values, window U-factors, blower door readiness.
Field Inspection Sequence
Each inspection must be scheduled and approved before the next phase of construction may proceed.
Footing / Foundation
Before pour. Verify frost depth (42"+ in New England), soil bearing, rebar placement, anchor bolt locations. Common fail: Insufficient frost depth, missing anchor bolts at plate ends.
Underground Utilities
Sewer/water/electrical trenching depth, pipe material, slope, bedding, separation distances. Common fail: Water lines too close to sewer, missing sand bedding.
Rough Frame
Structural connectors (Simpson Strong-Tie or equivalent), nailing schedules, shear wall installation, header sizing. Common fail: Missing hurricane clips, insufficient shear panel nailing.
Rough Mechanical
Rough plumbing (DWV testing), rough electrical (wire sizing, box fill), HVAC ductwork. Common fail: Missing GFCI/AFCI protection, incorrect wire gauge.
Insulation / Air Seal
Insulation installation quality (Grade I), air barrier continuity, blower door test preparation. Common fail: Compressed batts, gaps around penetrations.
Final Inspection
CO/smoke alarm verification, GFCI/AFCI testing, fixture operation, egress window operation, address posting. Certificate of Occupancy issuance.
Efficiency Note
Municipalities that provide this inspection sequence to homeowners and contractors at permit issuance report 30% fewer failed inspections and significantly reduced re-inspection trips.
Structural & Safety Best Practices
Foundation & Anchorage
Anchor Bolt Spacing — IRC R403.1.6
Maximum 6 feet on center and within 12 inches of each end of each sill plate section. This is a non-negotiable life-safety requirement.
Load Path Continuity
Every ADU must demonstrate a continuous load path from roof to foundation. Required approved connectors (e.g., Simpson Strong-Tie H2.5A) at each structural transition: rafter → top plate → stud → sill plate → foundation.
Frost Depth
Footings must extend below the frost line. In New England: typically 42" or greater. Check local frost depth maps or county soil survey.
Fire Separation Requirements
Detached, 5+ ft from property line
Standard construction per IRC. No fire-resistance rating on exterior wall.
Detached, <5 ft from property line
1-hour fire-resistance-rated exterior wall on the side facing the property line. 5/8" Type X gypsum on interior face.
Attached ADU
1-hour fire-resistance-rated separation between ADU and primary dwelling. Two layers 5/8" Type X or rated UL assembly.
ADU Over Garage
1-hour fire-resistance-rated floor/ceiling assembly between garage and living space. 5/8" Type X ceiling.
Special Conditions
Flood Zones (FEMA SFHA)
ADUs must be elevated to or above Base Flood Elevation (BFE) and use flood-resistant materials below BFE. Submit an Elevation Certificate (FEMA Form 086-0-33) with the permit application.
Seismic Design Categories D, E, F
Additional hold-down and shear wall requirements per IRC R602.10. Consult ASCE 7 hazard maps for your jurisdiction.
Wildfire-Urban Interface (WUI)
Class A roofing, ember-resistant vents, and non-combustible exterior materials within 5 feet of the structure.
Radon — EPA Zone 1
New ADU foundations should include radon-resistant construction per IRC Appendix F: sub-slab depressurization system or passive stack.
Model Submittal Package Requirements
The following document set constitutes the ADU Exchange Standard for a complete permit application. Municipalities that adopt this standard report a dramatic reduction in incomplete applications and front-counter questions.
Supplemental Documents (As Applicable)
Geotechnical report (unstable soils/flood zones) • Stormwater management plan (increased impervious surface) • Tree preservation plan (protected trees) • Historic district Certificate of Appropriateness • Septic system evaluation (Title 5 or equivalent).
Risk Mitigation for Municipalities
Objective standards and standardized processes are your best defense against legal challenge.
Equal Protection / Fair Housing
Standardized, objective rules ensure all applicants are treated identically regardless of race, national origin, familial status, or disability. Discretionary standards create vulnerability to disparate impact claims under the Fair Housing Act.
Takings / Due Process
Overly burdensome restrictions — excessive setbacks, unreasonable size caps, owner-occupancy mandates — may be challenged as regulatory takings. This framework uses standards vetted against prevailing case law.
State Preemption
An increasing number of states enact preemption statutes that override local prohibitions. Municipalities that proactively adopt compliant ordinances avoid the disruption of having state law imposed upon them.
Model Indemnification Language
Include in Every Permit Application
"Applicant agrees to indemnify and hold harmless the Municipality, its officers, agents, and employees from and against any and all claims, damages, losses, and expenses (including reasonable attorney fees) arising from or related to structural failures, code non-compliance, or personal injury associated with the permitted Accessory Dwelling Unit."
Insurance & Bonding
General Liability: Require proof of contractor general liability insurance ($1M minimum) as a condition of permit issuance.
Workers' Compensation: Require proof of workers' comp coverage for all contractors with employees.
Homeowner's Insurance: Recommend (not require) that homeowners notify their carrier of the ADU.
Model ADU Ordinance (Abridged Draft)
This model ordinance is provided as a starting point. Municipal counsel should review and adapt before adoption.
Article 1: Purpose & Intent
Establish clear, objective standards for ADUs to increase housing supply, provide options for family members/caregivers/essential workers, ensure public health and safety through IRC compliance, and support efficient use of existing infrastructure.
Article 2: Applicability
Applies to all lots in residential zoning districts (R-1 through R-4). ADUs meeting objective standards shall be approved ministerially by the Building Commissioner.
Article 3: Approval Process
Applications meeting all objective standards shall be approved within 60 days of a complete application. No public hearing, special permit, variance, or discretionary design review required.
Article 4: Dimensional Standards
900 sq. ft. or 50% of primary (whichever is less). 18–25 ft height. 4 ft side/rear setbacks. No minimum lot size. One ADU per lot.
Article 5: Parking
No additional parking for ADUs within ½ mile of transit, in historic districts, converted from existing space, or where on-street permits are available.
Article 6: Utilities & Infrastructure
ADUs may connect to existing laterals subject to DPW capacity verification. Separate metering encouraged but not required. No separate utility connection mandate if existing has capacity.
90-Day Implementation Roadmap
A phased rollout ensures staff readiness, stakeholder buy-in, and smooth launch.
Phase 1: Audit
Review existing zoning bylaws for ADU-prohibitive "poison pill" provisions: Special Permit requirements, minimum lot sizes, owner-occupancy mandates. Identify IRC edition currently adopted.
Phase 2: Draft
Use the Model Ordinance (Section 8) to draft a new ADU bylaw or amend existing ordinance. Circulate to municipal counsel for legal review.
Phase 3: Stakeholder Engagement
Host a Builder & Realtor Workshop. Conduct informational sessions for Select Board / City Council. The ADU Exchange provides facilitation support.
Phase 4: Staff Training
Train plan examiners and field inspectors on the submittal checklist (Section 6) and inspection workflow (Section 4). Distribute jobsite inspection cards.
Phase 5: Technology Setup
Upload the Complete Application Checklist to the town website. Configure online permitting portal with ADU-specific application type.
Phase 6: Launch
Begin accepting ADU applications. Designate a single ADU Coordinator point-of-contact for the first 90 days.
Phase 7: Post-Launch Review
90-day after-action review: track permit volume, average review time, inspection pass rate, and applicant feedback. Iterate and improve.
Common Municipal Pitfalls & How to Avoid Them
Requiring Special Permits for ADUs
Legacy zoning language that predates state ADU mandates. Creates backlogs, inconsistency, and legal exposure.
Excessive Setback Requirements
Applying the same setbacks as the primary dwelling eliminates viable ADU locations on most lots.
Mandatory Owner-Occupancy
Unenforceable, creates staff burden, and increasingly preempted by state law.
Parking Mandates
Outdated zoning assumptions about car ownership. Adds $20,000–$50,000+ per unit.
Subjective Design Review
Desire to protect character introduces discretion, delays, and Fair Housing vulnerability.
Prohibitive Impact Fees
Treating ADUs like new single-family homes for fee purposes discourages permitted construction.
Ignoring Existing Unpermitted Units
Overwhelmed enforcement staff and political inertia allow unsafe units to persist.
The ADU Exchange Partnership Model
The ADU Exchange is not just a document — we are your partner in implementation. We serve as the bridge between the town hall and the job site.
| Service | What We Provide | Your Benefit |
|---|---|---|
| Pre-Vetted Plan Sets | IRC-compliant ADU designs (studio, 1-BR, 2-BR, Carriage House) with complete construction documents. | Reduces plan review time by up to 60%. |
| Builder Certification | Training and certification for contractors on ADU-specific code challenges. | Better-prepared contractors pulling permits in your town. |
| Homeowner Education | Online resources, FAQ guides, step-by-step permitting walkthroughs. | Reduces walk-in questions at the building dept by up to 50%. |
| Ordinance Assistance | Review and markup of existing ADU ordinances with model language. | Avoids costly legal challenges and state preemption issues. |
| Inspector Training | On-site or virtual training on the ADU Exchange Inspection Framework. | Standardized inspection quality, fewer re-inspection trips. |
| Municipal Dashboard | Real-time tracking of ADU permits, review timelines, and inspection outcomes. | Data-driven program management with reporting for elected officials. |
ADU Permit Fee Calculator
The #1 question at the building department counter: "How much will this cost?" This calculator gives homeowners an instant fee estimate. Customize it with your fee schedule and embed it on your town website.
"Is My Lot Eligible?" Pre-Screening Tool
Reduce walk-in traffic by up to 40%. This 7-question wizard gives homeowners a Green / Yellow / Red eligibility assessment before they visit the building department. Embed on your town website.
ADU Financial Impact Estimator
The tool that gets the budget committee to say yes. Input your town's tax rate and projected ADU permits, and generate a 5-year revenue projection with ready-made talking points for elected officials.
ADU Amnesty & Legalization Pathway
Every municipality has unpermitted ADUs. An amnesty program brings them into compliance, prioritizes life safety over punishment, and expands your tax base. This is the political win that gets selectmen excited.
❌ Without Amnesty
Units remain hidden. No smoke alarms, no egress, no fire separation. Occupants at risk. $0 tax revenue. Liability exposure for the municipality.
✅ With Amnesty
Owners voluntarily come forward. Life-safety issues corrected. Units inspected and issued C.O. New permit fees + property tax revenue. Safer community.
The 4-Phase Legalization Process
Phase 1: Voluntary Disclosure
6–12 month windowHomeowners self-report. No fines for voluntary disclosure. Simplified 1-page application. Reduced fee ($500–$750 vs. $2,500+). Temporary occupancy authorization during review.
Phase 2: Life-Safety-Only Inspection
Within 30 daysFocused on: smoke/CO alarms, egress windows, no exposed wiring, GFCI in kitchen/bath, structural stability, fire separation, safe heating. NOT full current-code compliance.
Phase 3: Corrective Work
60–120 daysPrioritized punch list: Critical (immediate), Important (30 days), Standard (120 days). Homeowner hires any licensed contractor. Re-inspection upon completion.
Phase 4: Certificate of Occupancy
Upon passing re-inspectionRetroactive C.O. issued. Unit added to assessment. Homeowner notifies insurance. Unit is now legal, insurable, and counted in housing inventory.
Political Framing
Frame as a "Safety First" initiative: "We are not punishing homeowners — we are partnering with them to make every dwelling in our community safe." This framing is essential for elected official buy-in.
When the Neighbor Calls: Abutters' FAQ Script
Print this and keep it by the phone. Your staff needs a calm, factual script when an angry neighbor calls about the ADU next door.
"Is this legal? Can they really do this?"
Response: "Yes. Under [state law / our ordinance], ADUs meeting objective standards are a permitted use. The unit will be built to IRC standards and inspected by our department."
"Can I stop it?"
Response: "ADUs meeting objective standards are approved ministerially — no public hearing or abutters' notification. This is the same as a deck or finished basement."
"What about parking?"
Response: "ADU occupants generate 0.5–0.8 vehicle trips per day — far less than a new home. [Our ordinance waives/reduces parking for ADUs near transit/conversions.]"
"What about property values?"
Response: "Research shows well-built ADUs have neutral to slightly positive effects on surrounding values. The unit meets the same building codes as any new home."
ADU Construction Cost Estimator
The second question homeowners ask after "Can I build one?" is "What will it cost?" This tool gives realistic cost ranges by ADU type, finish level, and region — plus an ROI projection based on rental income. Reduces unrealistic expectations and helps homeowners budget properly.
Why This Helps Your Building Department
When homeowners understand true costs upfront, they hire qualified contractors, submit complete applications, and build code-compliant structures. Uninformed homeowners hire the cheapest bidder, cut corners, and fail inspections. Cost education is code compliance education.
Detached New Build
$150–$350/SF. The most expensive type but the highest ROI. Full foundation, framing, roofing, MEP, finishes. Budget $120k–$300k+ for a 650 SF unit.
Garage Conversion
$100–$200/SF. Existing structure saves on shell costs. Key expenses: insulation, HVAC, plumbing rough-in, electrical upgrade, egress windows. Budget $65k–$130k.
Basement Conversion
$80–$180/SF. Lowest cost path if ceiling height is adequate (7'+ finished). Challenges: moisture control, egress wells, natural light. Budget $50k–$115k.
Attached Addition
$130–$280/SF. Shares one wall with primary dwelling. Requires fire separation. Often the best balance of cost and livability. Budget $85k–$180k.
Septic & Sewer Decision Tree
Wastewater capacity is the #1 ADU project killer in New England. Your town can't deny an ADU based on zoning if it meets objective standards — but the Board of Health CAN deny it based on septic capacity. This decision tree routes homeowners to the right answer in 4 questions.
The #1 Rule
ALWAYS verify wastewater capacity BEFORE spending money on design. A $600 Title 5 inspection today prevents $10,000 in wasted design costs on an infeasible project. Put this on your website in bold, red text.
Public Sewer → Simplest Path
Get a DPW capacity letter. Connection fee $1,500–$5,000. No Title 5 needed. Proceed to building permit.
Septic 4+ BR with Spare Capacity → Likely Feasible
Title 5 inspection to confirm. If system passes with spare bedroom, 1-BR ADU is viable without upgrade.
Septic at Capacity → Upgrade Required
Conventional upgrade $15k–$25k. Innovative/alternative $25k–$45k. Must be budgeted from Day 1.
Cesspool → Full Replacement Required
Cesspools are illegal for expansion. Size the new system for home + ADU simultaneously. $25k–$50k.
Homeowner Journey Map
A 7-phase interactive guide that walks homeowners through the entire ADU process — from initial research to Certificate of Occupancy. Each phase includes checkable tasks, cost estimates, timelines, and the professional responsible.
When your front-counter staff gets the question "Where do I even start?", hand them this link. It's the single most powerful tool for reducing repeat inquiries and setting realistic expectations.
| Phase | Duration | Cost Range | Key Action |
|---|---|---|---|
| 1. Research | 1–2 weeks | Free | Check state law, run lot screener, visit building dept website |
| 2. Feasibility | 2–6 weeks | $500–$3,000 | Verify septic/sewer, get survey, confirm financing |
| 3. Design | 4–8 weeks | $3,000–$12,000 | Hire designer, compile submittal package |
| 4. Permits | 2–8 weeks | $1,500–$4,000 | Submit complete application, plan review |
| 5. Construction | 3–8 months | $80k–$350k+ | Foundation → framing → MEP → finishes |
| 6. Inspections | Throughout | Included | 6 inspection phases, corrections as needed |
| 7. Move In | 1–2 weeks | $500–$2,000 | C.O. issued, insurance updated, tenant moves in |
Municipal ADU Readiness Scorecard
How prepared is YOUR building department for ADU applications? This 30-question self-assessment covers 6 categories and generates a letter grade (A through F), a category breakdown, and a prioritized action plan. Takes 5 minutes.
Building commissioners: take this assessment with your team. It identifies exactly where your gaps are and what to fix first. The ADU Exchange offers a free 30-minute consultation to review your results.
Legal & Ordinance
State compliance, ministerial approval, objective standards, owner-occupancy
Application Process
Dedicated forms, checklist, fee schedule, turnaround time, status tracking
Technical Capacity
Plan examiner training, inspection checklists, fire separation policy, BOH coordination
Public Resources
Website, homeowner FAQ, fee calculator, multilingual materials, pre-screening
Data & Tracking
ADU-specific metrics, turnaround time, first-pass rates, revenue reporting
Risk Mitigation
Contractor insurance, indemnification, Fair Housing, fee defensibility, abutters' script
Abutters' FAQ Template — Staff Response Script
When the phone rings and it's an angry neighbor demanding to know "how can they build THAT next door?" — your staff needs a script. Not opinions. Not politics. Facts and law citations, delivered consistently every time.
This print-ready one-page document answers the 8 questions your front counter gets most, including:
"Is this legal? Can they really build this?"
Answer: Yes. Under [State Law Citation], ADUs meeting objective standards are a permitted use. The property owner has applied for / received a building permit. We review for code compliance — that's our job.
"Can I stop it? I want to oppose this."
Answer: ADUs meeting objective standards are approved ministerially — no public hearing, no ZBA, no abutters' notification. Same as a deck or bathroom addition.
"What about my property values?"
Answer: Research consistently shows a neutral to slightly positive effect. The unit meets the same building codes as any new home in our community.
"I want to talk to the Selectman / Mayor."
Answer: You're welcome to contact elected officials. However, building permit decisions are made by the Building Commissioner based on adopted codes — not by elected officials. This protects everyone.
Staff Protection
The script includes a de-escalation line: "I understand your concern. I've provided the factual information. If you'd like to provide written comments, you may send them to our office." This ends the call professionally without staff taking a political position.
Real-Time Code Amendment Tracker
Your state changes ADU law. You don't find out for 6 months. A homeowner walks in citing the new rule. Your staff is blindsided. This tool eliminates that scenario entirely.
The Code Amendment Tracker monitors all 6 New England states plus federal housing agency rules. Every update includes:
Impact Classification
Each amendment is tagged Critical (immediate action required), Major (ordinance update needed), Moderate (policy adjustment), or Informational. Building commissioners can prioritize at a glance.
Plain-English "What Changed"
No legislative jargon. Every update translates the legal text into: what the old rule was, what the new rule is, and the specific code sections affected.
"What You Must Do" Action Items
Concrete next steps for your municipality. "Remove subjective design review language." "Reduce impact fees to ≤50% of SFH rate." "Update parking ordinance within 60 days."
Model Ordinance Language
Ready-to-adopt clause text for each amendment. Send to municipal counsel for review — don't draft from scratch.
Push Notifications
Subscribe with your email and state. When a change hits, you get an alert the same day — not 6 months later when a homeowner catches you off guard.
ADU Financial Impact Estimator (Enhanced)
The Financial Impact Estimator (Section 14) has been upgraded with three new metrics that resonate with budget committees and town managers: construction jobs, enforcement cost savings, and legalization revenue.
| Metric | What It Calculates | Why It Matters |
|---|---|---|
| Construction Jobs | ~2.5 FTE per ADU project × total permits, plus 1.5x local economic multiplier | Elected officials love job creation numbers — ADUs are a private-sector stimulus |
| Enforcement Savings | Annual complaint costs × 60% reduction, projected over 5 years | By-right pathways reduce enforcement burden — money saved is money earned |
| Legalization Revenue | 30% of estimated unpermitted units × assessment uplift × tax rate | Unpermitted ADUs paying $0 in tax become revenue-generating, code-compliant housing |
| Housing Units Created | Total permits × 1.8 avg occupancy | Residents housed without public subsidy — the strongest affordable housing argument |
7 Ready-Made Talking Points
The enhanced estimator now generates 7 talking points auto-populated with your town's specific numbers. Copy-paste directly into your budget presentation, town meeting warrant article, or selectboard memo. Each talking point cites a specific dollar figure from YOUR inputs.
Multilingual Homeowner Guides
The communities that need ADUs most — immigrant families, multigenerational households, working-class neighborhoods — are often the communities least served by English-only government documents. Language access isn't just good policy. It's a Fair Housing obligation.
The ADU Exchange provides the complete homeowner fact sheet in 5 languages, formatted for print, ready to place at your front counter, library, and community centers:
English
Base version
Español
Spanish
Português
Portuguese
中文
Mandarin
Kreyòl
Haitian Creole
Each translation covers the same essential content: what an ADU is, eligibility criteria, cost ranges, the 6-step permit process, key rules, and the wastewater warning. Every version is print-formatted for double-sided letter paper.
For Your Building Department
Replace [Municipality Name] and [Building Department Phone] with your town's info. Print 25 copies of each language. Place in a multi-pocket rack at the front counter. Add a "Available in: 🇺🇸 🇪🇸 🇧🇷 🇨🇳 🇭🇹" sign. Your town just became the most accessible ADU program in New England — and you've documented your Fair Housing compliance.
The Golden Rule for Municipalities
"The best ADU ordinance is one that turns your building inspector into a code compliance partner — not a gatekeeper. If the rules are clear, the inspector's job gets easier, the homeowner gets it right, and the community gets safer housing."
Complete IRC Cross-Reference Appendix
Every code section cited in this guide mapped to specific ADU inspection checkpoints. This appendix is designed to live in your plan examiner's desk drawer — a single reference that connects every ADU-specific requirement to the exact IRC section, the inspection phase where it's verified, and the most common deficiency encountered.
Structural & Foundation
| IRC Section | Discipline | Requirement | ADU Checkpoint | Common Deficiency |
|---|---|---|---|---|
| R403.1 | Structural | General footing requirements: minimum width, thickness, and depth below undisturbed ground | Footing/Foundation inspection | Footings poured on disturbed/uncompacted soil; insufficient width for 2-story ADU loads |
| R403.1.1 | Structural | Minimum footing size based on number of stories and soil bearing capacity (Table R401.4.1) | Footing/Foundation inspection | Default 16" width used without verifying soil bearing capacity; undersize for 2-story |
| R403.1.4 | Structural | Minimum depth of footings below undisturbed ground: 12" minimum, below frost line | Footing/Foundation inspection | Footing above frost line (42"+ in New England). #1 structural deficiency for ADUs |
| R403.1.6 | Structural | Anchor bolt placement: ½" minimum, 6' O.C. max, within 12" of each plate end | Footing/Foundation inspection | Anchor bolts missing at plate section ends; bolts not embedded 7" into concrete |
| R602.3 | Structural | Wood stud design values, sizes, and framing requirements per Table R602.3(5) | Rough Frame inspection | Undersized studs for bearing walls; studs not continuous from sill to top plate |
| R602.3.2 | Structural | Top plate lap splice: 48" minimum with eight 16d nails on each side of splice | Rough Frame inspection | Lap splices at stud locations only (insufficient); wrong nail count/size |
| R602.7 | Structural | Headers required over openings in bearing walls; sizing per Table R602.7(1) | Rough Frame inspection | Undersized headers for wide window/door openings; missing jack studs |
| R602.10 | Structural | Wall bracing requirements: type, amount, and location per seismic/wind zone | Rough Frame inspection | Insufficient shear wall panels; missing hold-downs at shear wall ends |
| R802.5 | Structural | Allowable rafter spans per Table R802.5.1; ridge board/beam requirements | Rough Frame inspection | Rafter spans exceeded; ridge board missing or undersized for opposing rafters |
Fire Safety & Separation
| IRC Section | Discipline | Requirement | ADU Checkpoint | Common Deficiency |
|---|---|---|---|---|
| R302.1 | Fire | Exterior wall fire-resistance rating based on fire separation distance (Table R302.1(1)) | Plan Review + Rough Frame | No fire-rated assembly on wall within 5' of property line; penetrations not sealed |
| R302.2 | Fire | Townhouse (attached unit) separation: 1-hour fire-resistance-rated wall | Plan Review + Rough Frame | Single layer drywall instead of required double 5/8" Type X; unsealed top plate |
| R302.6 | Fire | Dwelling/garage separation: ½" gypsum on garage side (1-hr if habitable above) | Rough Frame + Insulation | Missing ceiling drywall in garage below ADU; untaped joints in fire-rated assembly |
| R302.13 | Fire | Fire sprinkler requirements (where required by jurisdiction) | Plan Review | Jurisdiction requires sprinklers for ADUs but not verified at plan review stage |
| R314.3 | Life Safety | Smoke alarm locations: every sleeping room, outside each sleeping area, each story | Final Inspection | Missing alarm in ADU hallway; not interconnected with primary dwelling alarms |
| R315.1 | Life Safety | CO alarm required outside each sleeping area and on every level with fuel-burning appliance | Final Inspection | Missing CO alarm in ADU with gas heating; battery-only instead of hardwired |
| R310.1 | Life Safety | Emergency egress: min 5.7 sq ft opening, 24" min height, 20" min width, 44" max sill | Plan Review + Final | Window sill height exceeds 44"; net clear opening below 5.7 sq ft after screen |
Plumbing, Electrical & Energy
| IRC Section | Discipline | Requirement | ADU Checkpoint | Common Deficiency |
|---|---|---|---|---|
| P2503 | Plumbing | Inspection and testing of DWV and water distribution systems | Underground + Rough Mech | DWV test not performed before cover; leaking joints at ABS/PVC transitions |
| P2603.5.1 | Plumbing | Freezing protection: water pipes in exterior walls insulated or heat-traced | Insulation/Air Seal | Supply lines in exterior wall cavity without insulation board behind; freeze risk |
| P2801 | Plumbing | Water heater installation: T&P relief valve, drain pan, expansion tank where required | Rough Mech + Final | Missing T&P discharge piping; drain pan not connected to approved receptor |
| E3601 | Electrical | Service sizing: adequate for ADU load calculation per Article 220 | Plan Review | Existing 100A service insufficient for primary + ADU; sub-panel feed undersized |
| E3902.1 | Electrical | GFCI protection: kitchen, bathrooms, laundry, outdoors, garages, crawlspaces | Rough Mech + Final | GFCI missing at kitchen island outlet; bathroom receptacles on non-GFCI circuit |
| E3902.16 | Electrical | AFCI protection: bedrooms, living rooms, hallways, closets, dining rooms | Rough Mech + Final | AFCI breakers not installed for bedroom circuits; nuisance tripping not resolved |
| IECC R402 | Energy | Building thermal envelope: insulation R-values per climate zone (Table R402.1.2) | Insulation/Air Seal | R-values below minimum for climate zone; insulation compressed at narrow cavities |
| IECC R402.4 | Energy | Air leakage: 3-5 ACH50 maximum (by climate zone); blower door test required | Insulation/Air Seal | Failed blower door; unsealed penetrations at electrical boxes, plumbing, HVAC boots |
Plan Examiner Tip
Print this appendix double-sided and laminate it. Every plan examiner and field inspector in your department should have one. The ADU Exchange provides laminated jobsite cards keyed to each inspection phase — contact us for bulk ordering.
ADU Case Law Database
Precedent-setting ADU permit appeals organized by issue. Understanding these cases protects your municipality from repeating the mistakes of others. Each case includes the issue, the outcome, and the actionable takeaway for your building department.
Disclaimer
These case summaries are for educational purposes only and do not constitute legal advice. Municipal counsel should be consulted for jurisdiction-specific guidance. Case law evolves; verify current status before relying on any precedent.
Setbacks & Dimensional Standards
Homeowner proposed a detached ADU 3.2 feet from the rear property line. Town denied under 10-foot setback requirement that predated the Affordable Homes Act. Homeowner appealed, arguing state law preempted the local setback for ADUs.
HOA challenged the city's approval of a 22-foot-tall detached ADU that complied with city code but exceeded HOA height restrictions. HOA argued the ADU impacted property values and neighborhood character.
Owner-Occupancy & Density
Coalition challenged the city's owner-occupancy requirement for ADU permits, arguing it created a disparate impact on renters and disproportionately affected minority homeowners with lower rates of outright ownership.
Town denied ADU permit on the basis that approving it would exceed the "maximum density" allowed under local zoning — despite state law explicitly stating ADUs shall not be counted toward density calculations.
Design Review & Discretionary Denial
City's Design Review Board denied an ADU based on "incompatible visual impact on neighborhood character." Applicant argued the standard was subjective and violated the state's ministerial approval mandate.
City charged $28,000 in impact fees for a 650 sq. ft. ADU — the same fee schedule applied to new single-family homes. Applicant challenged as disproportionate and a de facto prohibition.
State Preemption Enforcement
State AG sued the town for maintaining an ADU prohibition after the state passed HB 6107 legalizing ADUs statewide. Town argued its opt-out was valid; AG argued the opt-out procedure was not properly followed.
Town required a "special permit with conditions" for ADUs — including mandatory design review and abutters' notification — after the Affordable Homes Act mandated ministerial approval. Applicant challenged the process.
State Preemption Matrix
Side-by-side comparison of ADU legislation across New England states with municipal compliance requirements. Updated for the 2025–2026 legislative session. Your zoning officer should check this matrix before denying any ADU application.
| State | Status | Key Statute | Max Size | Approval Path | Parking | Owner Occ. | Septic/Sewer | Municipal Landmine |
|---|---|---|---|---|---|---|---|---|
| MA | By-Right | Affordable Homes Act (2024) | 900 SF / 50% | Ministerial — no hearing, no SP | None within ½ mi transit | Not required | Title 5 still applies; DEP controls flow | Septic capacity is #1 project killer. Towns cannot block but DEP can. |
| RI | By-Right | H 5512 / S 2040 (2024) | Per local code | By-right on 20k+ SF lots or internal conversion | None for conversions | Not required | Capacity verification required | STR ban: state prohibits ADU use as Airbnb. 30-day minimum lease. |
| NH | By-Right | HB 577 (2025) | 750–950 SF (local) | By-right attached + detached | 1 space max | Not required | State septic rules apply | Size caps vary by town. Always verify local FAR before quoting. |
| ME | Growth Areas | LD 1829 (2023) | Per local code | Up to 4 units on public sewer; ADU no longer requires sprinklers | Varies by town | Varies | Public sewer required for density bonus | Growth ordinance delays in some municipalities. Check for moratoriums. |
| VT | Act 47 | Act 47 (2023) | 900 SF / 30% | Must be allowed; same dimensional rules as SFH | Per local code | Not required | Act 250 + local sewer allocations | Wastewater capacity is the bottleneck. Act 250 review for larger lots. |
| CT | Opt-Out | HB 6107 (2023) | Per local code | By-right unless town opted out | Varies | Varies | Per local code | Most high-value coastal towns opted out. Verify before pulling permit. |
National Trends to Watch
California SB 9 / AB 68 Model
California's aggressive preemption model — allowing lot splits + ADUs simultaneously — is being studied by legislatures in Washington, Oregon, Colorado, and Montana. Expect this pattern to spread to New England within 3–5 years.
Federal ADU Financing Rules
FHA and Fannie Mae now allow ADU rental income to qualify for mortgage underwriting. This dramatically expands the pool of homeowners who can finance ADU construction — expect permit volume to accelerate.
Impact Fee Litigation Wave
Post-Martinez, impact fee challenges are proliferating nationally. Municipalities charging flat per-unit fees for ADUs should expect legal challenges. Proportional fee schedules are the defensible standard.
Annotated Plan Review Workflow
Complete plan review workflow with pass/fail criteria for each discipline. Click each discipline to expand the full checklist. Every item includes the IRC citation so your examiners can cite the code — not just their opinion.
Structural Review
▼Foundation type identified and appropriate for soil/site
Verify slab-on-grade, crawlspace, or full basement. Confirm geotechnical report if required by site conditions.
IRC R401.4, Table R401.4.1Footing dimensions meet minimum for building loads
Check footing width and depth against Table R403.1. Verify rebar placement (#4 bars, 2 continuous for residential).
IRC R403.1, R403.1.3COMMON FAIL: Frost depth not specified on plans
Plans must state footing depth relative to frost line. "42 inches below grade" or "below frost line" is required notation. Reject plans without this callout.
IRC R403.1.4Anchor bolt schedule shown on foundation plan
Verify ½" bolts at 6' O.C. maximum, within 12" of each plate end and each side of openings. Must be embedded 7" minimum.
IRC R403.1.6Continuous load path from roof to foundation
Verify connector schedule: rafter-to-plate, plate-to-stud, stud-to-sill, sill-to-foundation. Manufacturer and model specified.
IRC R301.1, R602.3Header schedule for all openings in bearing walls
Verify header sizes per Table R602.7(1). Check for jack studs at each side of header. King studs specified.
IRC R602.7Shear wall locations and details
Verify braced wall panel locations per R602.10. Check nailing schedules for sheathing. Hold-down hardware specified at panel ends.
IRC R602.10, R602.10.4Life Safety & Fire Review
▼Egress windows in every sleeping room
Minimum 5.7 sq ft net clear opening. Minimum 24" height, 20" width. Maximum 44" sill height from finished floor. Mark on floor plan.
IRC R310.1, R310.2COMMON FAIL: Egress window net clear opening not calculated
Window schedules often show rough opening or frame size — not net clear. Require manufacturer data sheet showing net clear opening meets 5.7 sq ft.
IRC R310.1.1Smoke alarm locations shown on floor plan
Required in every sleeping room, outside each sleeping area in the immediate vicinity, and on each story of the ADU.
IRC R314.3CO alarm locations shown on floor plan
Required outside each sleeping area and on every level with a fuel-burning appliance or attached garage. Hardwired with battery backup.
IRC R315.1, R315.3Fire separation assembly specified (if applicable)
1-hour assembly for: attached ADU, ADU within 5' of property line, ADU over garage. UL assembly number required on plans.
IRC R302.1, R302.2, R302.6Interconnection of alarms between ADU and primary dwelling
Verify whether local amendment requires interconnection between ADU and primary dwelling alarm systems. Default IRC does not require this for detached ADUs.
IRC R314.4 + local amendmentsElectrical Review
▼CRITICAL: Service load calculation for primary + ADU
Existing service (often 100A or 150A) must support both primary dwelling and ADU loads per Article 220. If insufficient, service upgrade required before ADU permit.
IRC E3601, E3602Sub-panel location, size, and feed conductor sizing
Sub-panel for ADU typically 60A–100A. Verify feeder conductor sizing per Table E3603.1. Verify overcurrent protection at main panel.
IRC E3603, E3706GFCI protection locations identified
Kitchen countertop receptacles, bathrooms, laundry area, outdoors, garages, crawlspaces, unfinished basements. Mark on electrical plan.
IRC E3902.1–E3902.11AFCI protection for living areas
Required for: bedrooms, living rooms, parlors, libraries, dens, sunrooms, recreation rooms, closets, hallways, dining rooms, similar areas.
IRC E3902.16EV-ready conduit (where required by state/local code)
Increasing number of jurisdictions require EV-ready infrastructure for new construction. Verify local amendment. Minimum: empty conduit from panel to future charging location.
Local amendment / state energy codePlumbing Review
▼Fixture count and DWV sizing verified
Calculate total fixture units. Verify building drain, building sewer, and vent sizing per Tables P3004.1 and P3107.2.
IRC P3004, P3107Water heater specifications and installation details
Verify fuel type, BTU rating, temperature setting (120°F max), T&P relief valve discharge, drain pan, and expansion tank (closed system).
IRC P2801, P2803, P2804COMMON FAIL: Sewer/septic capacity not verified
For properties on municipal sewer: DPW capacity letter required. For properties on septic: Title 5 (or equivalent) capacity analysis showing the system can support additional bedrooms.
Local health code / Title 5Backflow prevention verified
Verify backflow preventer on potable water supply. Verify air gap or check valve on dishwasher and washing machine drain connections.
IRC P2902Energy Code Review
▼Compliance path identified: Prescriptive or Performance
Prescriptive: verify R-values per Table R402.1.2 for your climate zone. Performance: HERS rating or REScheck report attached.
IECC R401.2Insulation R-values specified for all assemblies
Ceiling/attic, exterior walls, floor/foundation, slab edge. Verify cavity + continuous insulation where required (e.g., Zone 5: R-20 or R-13+5ci).
IECC Table R402.1.2Window U-factor and SHGC verified
Verify all fenestration meets maximum U-factor and SHGC for climate zone. Check NFRC labels on window schedule.
IECC Table R402.1.2Blower door test requirement noted
Most climate zones require blower door test: 3 ACH50 (Zone 5+) or 5 ACH50 (Zones 1-4). Note test requirement on permit for final inspection.
IECC R402.4.1.2Inspection Deficiency Reference
The most common ADU construction deficiencies encountered by field inspectors, organized by severity and inspection phase. Each entry includes the IRC violation, a description of what inspectors will see in the field, and the required corrective action.
Critical Deficiencies — Stop Work Required
Footing Above Frost Line
Footing bottom does not reach the required frost depth (42"+ in New England). Will result in frost heave, foundation cracking, and structural failure.
IRC R403.1.4 — Frost ProtectionMissing Fire-Rated Assembly
ADU within 5 feet of property line or attached to primary dwelling without required 1-hour fire-resistance-rated wall assembly. Life-safety hazard.
IRC R302.1 — Exterior Wall RatingNon-Compliant Egress Window
Bedroom window net clear opening below 5.7 sq ft, sill height above 44", or window will not fully open. Occupant cannot escape during fire.
IRC R310.1 — Emergency EscapeMissing Anchor Bolts at Plate Ends
Sill plate not anchored within 12" of plate end or at mudsill splices. Building can shift off foundation in seismic or high-wind event.
IRC R403.1.6 — Anchor BoltsMajor Deficiencies — Correction Required Before Cover
Missing GFCI Protection
Kitchen, bathroom, or exterior receptacles not on GFCI-protected circuits. Electrocution hazard near water sources.
IRC E3902.1–E3902.11Missing Hurricane Clips / Rafter Ties
Rafter-to-top-plate connection relies on toenails only — no approved metal connectors. Roof can separate from walls in high wind.
IRC R802.11, R602.3Unsealed Penetrations in Fire-Rated Assembly
Electrical boxes, plumbing penetrations, or HVAC boots pass through fire-rated wall/ceiling without approved firestopping. Compromises fire rating.
IRC R302.4 — PenetrationsFailed Blower Door Test
Air leakage exceeds maximum ACH50 for climate zone. Typically caused by unsealed penetrations, missing air barrier at rim joist, or uncaulked bottom plates.
IECC R402.4.1.2 — TestingMinor Deficiencies — Correction Required Before Final
Smoke/CO Alarm Not Interconnected
Alarms are present but not interconnected (all alarms sound when one activates). Battery-only alarms installed instead of hardwired + battery backup.
IRC R314.4, R315.3Address Not Posted on ADU
ADU does not have a visible address number for emergency services. Unit designation (e.g., "A" or "Unit 2") not assigned.
IRC R319.1 — Address NumbersModel Permit Forms & Templates
Ready-to-customize permit application forms, indemnification agreements, and inspection checklists. Each template is designed to be placed on your town website as a downloadable PDF — reducing front-counter confusion and ensuring complete applications from Day 1.
ADU Permit Application Form
Complete application form with project narrative, owner/contractor info, scope checkboxes (new build / conversion / addition), and septic/sewer declaration. Pre-formatted with your municipality's letterhead.
Complete Application Checklist
The full Section 6 submittal checklist (G-001 through P-101) as a standalone handout. Front-counter staff hand this to every walk-in inquiry. Checkboxes for applicant self-verification.
Indemnification & Hold Harmless Agreement
Model indemnification clause formatted as a signature page for attachment to permit applications. Reviewed by municipal law attorneys in 3 states.
Field Inspection Checklist (6-Phase)
Laminated jobsite card format. One card per inspection phase with pass/fail checkboxes and IRC code citations. Inspector signs and dates each phase.
Plan Review Routing Sheet
Internal routing sheet for multi-discipline plan review. Tracks structural, fire, plumbing, electrical, and energy reviews with examiner initials, comments, and re-review status.
Homeowner ADU Fact Sheet
Plain-language 2-page overview for homeowners: "What is an ADU? What does it cost? How do I apply?" Reduces front-counter questions by up to 50% when posted on your website.
Septic/Sewer Capacity Verification Form
Standardized form for DPW or Health Department to certify sewer/septic capacity for ADU bedrooms. Prevents the #1 project delay in New England.
Insurance & Bonding Verification Form
Contractor insurance verification form: general liability ($1M min), workers' comp, and license verification. Attach to permit as condition of issuance.
Bulk Customization
The ADU Exchange provides all 8 templates customized with your municipality's name, logo, contact information, and local code amendments. One-time setup, delivered in 5 business days.
Municipal Dashboard & KPI Tracking
What gets measured gets managed. The following KPIs should be tracked from Day 1 of your ADU program launch. They provide data-driven management for your building commissioner and reporting ammunition for elected officials.
Core KPIs — Track Monthly
Sample data from a mid-size New England municipality 6 months post-ADU Exchange implementation
Full KPI Framework
| KPI | Target | Why It Matters | Data Source |
|---|---|---|---|
| Applications Received (Monthly) | Upward trend | Measures demand and awareness. Declining numbers may indicate outreach gaps or a burdensome process. | Permitting system |
| Complete Application Rate | ≥85% | Measures whether your checklist and website resources are working. Below 85% = update materials. | Plan review intake log |
| Average Days: Application → Permit | ≤30 days | State mandates may require 60-day turnaround. Under 30 days signals a healthy, efficient department. | Permitting system dates |
| First-Pass Plan Review Rate | ≥80% | Plans approved without resubmittal. Below 80% indicates checklist deficiency or education gap. | Plan examiner logs |
| First-Pass Field Inspection Rate | ≥75% | Inspections passed on first visit. Reduces re-inspection trips and inspector workload. | Inspector daily logs |
| Top 3 Plan Review Rejections | Track categories | Identifies systemic gaps. If 60% of rejections are "missing egress calc," update checklist emphasis. | Plan examiner notes |
| Top 3 Field Inspection Failures | Track categories | Feed back into contractor education. If "missing hurricane clips" dominates, target builder training. | Inspector field notes |
| ADU Permits as % of Total Permits | Benchmark | Measures ADU program scale relative to overall building activity. National benchmark: 8–15%. | Permitting system |
| Revenue Generated (Permit Fees) | Track cumulatively | Demonstrates ROI of the ADU program to elected officials. Include permit fees + estimated property tax uplift. | Finance department |
| Unpermitted ADU Complaints | Downward trend | Measure of whether the by-right pathway is successfully bringing construction into compliance. | Code enforcement logs |
ADU Exchange Municipal Dashboard
We provide a hosted dashboard that automatically tracks these KPIs using data from your existing permitting system. Real-time charts, quarterly reports for elected officials, and benchmarking against peer municipalities. No IT integration required — we work with CSV exports from any permitting software.
Public Hearing Presentation Guide
Presenting a new ADU ordinance to your Select Board, City Council, or Town Meeting requires a specific narrative. Below is the slide-by-slide framework for a 20-minute presentation that has been battle-tested in 15+ New England municipalities.
Recommended Slide Deck (12 Slides)
Handling Common Objections
"Won't this change the character of our neighborhood?"
A: "Our objective compatibility standards require ADUs to match the primary dwelling in materials, roof pitch, and entry scale. These are not apartment buildings — they are small, subordinate structures that are architecturally compatible by code. And unlike discretionary design review, these objective standards actually protect character consistently for every applicant."
"What about parking and traffic?"
A: "National research shows ADUs generate 0.5–0.8 additional vehicle trips per day — far less than a new single-family home. Parking exemptions near transit reflect that ADU occupants in walkable areas own fewer cars. For context, our current zoning allows two-car garages on every lot but doesn't require that anyone use them."
"What about septic capacity?"
A: "This ordinance does not override the Board of Health or Title 5. Septic capacity must still be verified before any ADU permit is issued. What we are doing is removing the zoning barrier so that homeowners who have the capacity can proceed without a 6-month ZBA process."
"What if investors buy up houses just to build ADUs?"
A: "At 900 sq ft maximum, ADU rental income does not fundamentally change the economics of single-family investment. Investors are already buying homes in our community. The question is whether we want them to build unpermitted, unsafe units in the shadows — or permitted, inspected units that meet the IRC."
"Can't we just keep requiring special permits?"
A: "Our state law now requires ministerial approval for code-compliant ADUs. Maintaining a special permit requirement exposes us to legal action, as other municipalities have already discovered. Proactive compliance is both legally safer and administratively more efficient."
Presentation Support
The ADU Exchange provides a fully designed PowerPoint presentation customized with your town's data, peer comparisons, and local photos. We can also provide a staff member to co-present alongside your Planning Director at no additional charge for municipal partners.
The Advanced Technical Standard
"The municipalities that thrive don't just legalize ADUs — they operationalize them. The difference between a town with 3 ADU permits per year and 30 is not the ordinance. It's the infrastructure: the checklists, the trained inspectors, the educated contractors, and the political will backed by data."
⬆ Scroll up for Advanced Technical content
This track includes all Municipal Guide content (Sections 01–11) plus the 8 Advanced Technical modules above. Switch to the "Municipal Guide" tab to view the core content.