A finished backyard cottage — the kind of small permanent dwelling Chattanooga ADU rules are built around.

You already know an ADU in Chattanooga is not free. What you need next is clearer: Am I allowed on this lot? City or county? What do I bring to pre-submittal? Which drawings move a package? What gets plans bounced? How long? Who pulls the permit?

This field guide is for Chattanooga and Hamilton County homeowners (and adult kids helping parents) who are past the rough budget talk and ready to get permit-ready. It is not a cost article and not a brochure. For size, setbacks, and height, use our backyard ADU guide. For garage conversion versus new-build dollars, use the 2026 ADU cost breakdown.

Rules and portals change. Verify anything critical with the City Land Development Office or Hamilton County Building Inspections before you bid or pour.

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Start With the Jurisdiction Fork (City vs County)

Start with the lot: city vs county, setbacks, and whether a second structure can actually fit behind the house.

A Hixson mailing address does not automatically mean city rules. Ooltewah and East Brainerd parcels are often unincorporated. The wrong office means the wrong owner-occupancy answer, the wrong sewer answer, and a redesign.

How to check: Look up the parcel on Hamilton County GIS / tax maps, or ask staff which office has building-permit jurisdiction. Inside city limits → Land Development Office. Unincorporated county → Building Inspections at 4005 Cromwell Road.

Decision point	City of Chattanooga	Unincorporated Hamilton County
Building permit office	Land Development Office / Development Resource Center; apply online	Hamilton County Building Inspections (4005 Cromwell Rd); online apply at buildinginspection.hamiltontn.gov
Online portal (current city page)	OpenGov — chattanoogatn.portal.opengov.com	County Building Inspection online applications site
ADU legalization	Citywide ordinance effective June 14, 2022; max size raised to 800 sq ft in 2024	Hamilton County ADU standards are set in recent county resolution text. Verify current applicability with County Building Inspections or the Regional Planning Agency before you bid.
Size band	200–800 sq ft exterior; conditioned lofts/stairwells count	Resolution text caps ADU classification at 800 sq ft exterior (larger = different “secondary dwelling” path)
Owner occupancy	Not required by city ADU ordinance	Resolution text requires owner to live in the main house or the ADU
Septic	Sewer preferred; utility review is site-specific	Resolution text: ADUs not permitted on individual septic — public sanitary sewer required
Short-term rental	Separate STR certificate; absentee STRs limited by zone	Resolution text prohibits using the ADU as a short-term vacation rental
A-1 Agricultural	City allows ADUs in A-1 (among listed zones)	Resolution text: ADUs not permitted in County A-1
Pre-submittal / intake help	LDO pre-submittal, typically Tue & Thu mornings — 423-643-5894	Call Building Inspections — 423-209-7860

If your lot is unincorporated county, treat setbacks, utilities, and owner-occupancy rules as parcel-specific. Do not design an Airbnb-first unit, a septic-lot ADU, or an absentee-owner ADU on county land from a blog post alone — verify requirements with County Building Inspections or the Regional Planning Agency first.

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Are You Allowed? A Fast Eligibility Filter

Permanent construction — framing, loft, and insulation on a real ADU build. Tiny homes on wheels do not qualify.

Before you buy full drawings, run this filter out loud.

Usually a yes path (city lots):

• A single-family detached house already (or building one with a separate ADU permit).
• A zone that allows ADUs (CHCRPA common list: A-1, C-NT, RN-1-5, RN-1-6, RN-1-7.5, RN-2, RN-3, TRN-1, TRN-2, TRN-3; Form-Based Code areas use their own chart).
• One ADU, same ownership as the main house — no condo split or separate sale.
• A permanent foundation (tiny homes on wheels are not an ADU path).
• Exterior size 200–800 sq ft, with conditioned loft/stair area counted.

Hard stops or heavy friction:

• Duplex, townhouse, condo, or apartment as the main unit.
• HOA covenants that ban second dwellings or rentals (city approval does not override the HOA).
• Historic district without a Certificate of Appropriateness plan (St. Elmo, Ferger Place, Fort Wood, Battery Place, and others).
• County lot on septic, county A-1, or an owner who will not live in either unit — if resolution text is in force, those fail before drawings matter.
• Front-yard placement for a detached unit — detached ADUs belong in the rear or side yard.

For attached family suites, see mother-in-law suite construction. A true second dwelling still clears the same ADU zoning gate.

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What “Permit Ready” Actually Means

Permit-ready means complete drawings: site plan, floor plans, and the Height Determination Form — not a napkin sketch.

Permit ready is not “we have a floor plan we like.” It means a reviewer can answer yes to:

1. Jurisdiction and zone are correct.
2. Use qualifies as an ADU (one unit, same lot, same ownership, size/height/setback path identified).
3. Site plan proves the pad, setbacks, parking replacement (if any), and major utilities.
4. Floor plans show independent living: cooking, sleeping, bathing, egress.
5. Height Determination Form matches how zoning measures height (especially detached).
6. Trade scopes are ready for electrical, plumbing, and mechanical permits as needed.
7. Outside constraints are acknowledged: HOA, historic overlay, flood/hillside, EPB, sewer.
8. Who pulls the permit matches intended use (owner-builder personal use vs licensed contractor if you will rent).

Until those eight are honest, finish selections are entertainment, not permitting.

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Printable Document Checklist (Bring This to Pre-Submittal)

Use this as a working list for a City of Chattanooga ADU. County applicants should bring the same package bones and ask Building Inspections what their intake checklist adds or renames.

Must-have application package (city ADU guidance)

• Online building permit application (city residential page directs applicants to the OpenGov portal; paper forms are not accepted)
• Scaled site plan
• Floor plans of the ADU (plus enough main-house context for attached conversions)
• Height Determination Form
• Application fee after staff review / approval notice — amounts on the live city fee schedule; do not rely on blog numbers

Site plan content reviewers expect to see

• Property lines and lot dimensions
• Existing house, garage, decks, sheds — labeled
• Proposed ADU footprint with exterior dimensions (prove ≤ 800 sq ft)
• Setback dimensions to side, rear, and street lot lines
• Driveway, parking stalls, and replacement parking if a garage conversion removes a stall serving the main house
• Utility routes / connection notes (water, sewer status, electric)
• North arrow and graphic scale
• Easements, alleys, flood or steep-slope notes if they affect the pad

Add when the design needs them

• Exterior elevations (height and historic review)
• Structural / engineering drawings (new detached, loft loads, slope foundations, compromised garage framing)
• Electrical, plumbing, and mechanical layouts or notes sufficient for trade permits
• Energy / insulation approach consistent with current residential code
• Second means of egress called out clearly if the unit is 701–800 sq ft (two exit doors; garage doors do not count)
• Prefab / modular: factory engineering and/or State seal path documented

Outside agencies and private rules

• EPB service path for new or upgraded electric
• Water / sanitary sewer connection plan (or documented septic status — critical on county lots)
• Separate trade permits as required
• New address request via Hamilton County GIS if the ADU needs its own address (423-209-7760 / GIS@hamiltontn.gov)
• Tennessee One Call before digging (811)
• HOA architectural approval or written confirmation that none apply
• Historic Certificate of Appropriateness if applicable (Historic Zoning Commission — 423-643-5834)
• Contractor license, TN business license, and workers’ comp / exemption docs if a contractor pulls the permit

Print it. Check boxes before you walk into the Development Resource Center.

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Step-by-Step: Pre-Submittal → Application → Review → Inspections

After approval, inspections follow the build: framing, trades, insulation, drywall, final.

1. Pre-submittal meeting (city)

The city strongly recommends a pre-submittal meeting with Land Development Office staff before you buy a full drawing set. Meetings are typically Tuesday and Thursday mornings. Call 423-643-5894 to schedule. Multiple departments can sit in — that is the point.

Bring or have on a tablet:

1. Parcel address and tax map / parcel ID
2. Rough site sketch or survey
3. Photos of yard, slope, existing garage, and street frontage
4. Preferred path: garage conversion vs new detached vs attached
5. Honest target size (including loft/stair math)
6. Written questions: parking replacement, sewer tap, height measurement method, historic overlay, flood/hillside

Ask staff about your parcel: exact setbacks, Height Determination Form method, whether parking replacement is required, whether overlays add steps, and whether a concurrent main-house remodel needs separate permits.

County lots: call 423-209-7860 and ask what the equivalent early conversation looks like for an ADU — do not assume the city Tuesday/Thursday slot applies.

2. Prepare the complete digital package

Complete means site plan + floor plans + Height Determination Form + application fields + any historic/HOA attachments that apply. Incomplete packages create the “5–10 days” myth: the clock that matters starts after staff have something reviewable.

3. Submit online

City: Apply through the OpenGov portal linked from the residential building permit page (24/7). At the Development Resource Center, staff can help you submit digitally at the kiosk — paper is not accepted. You should get email confirmation of receipt and later approval.

County: Register/login at the Hamilton County Building Inspection online applications site. Licensed contractors can often pay fees online; other owners may apply online but typically pay at the office.

4. Plan review

City CHCRPA guidance: complete packages are typically reviewed in about 5–10 business days, depending on volume. That is plan review only — not design, revisions, utility taps, or construction. Treat it as a typical band, not a guarantee.

5. Pay the fee when notified

City practice: the building permit fee is due after staff review, when you get the payment notice. Pay online (card fees apply) or by check at the Land Development Office (cash no longer accepted per city guidance). live amounts on the official residential fee schedule; trade fees and utility costs sit on top.

6. Build and request inspections

Request inspections through the portal at least 24 hours ahead. Busy periods can run 48 hours or more. Have approved plans on site. A full ADU often includes foundation (new detached), framing/egress, trades, insulation, and final — your permit conditions list the exact sequence.

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Who Pulls the Permit?

Licensed Tennessee contractors (BC, BC-A, or BC-A/r within its valuation limit) typically pull residential / ADU permits, with workers’ comp documentation (or exemption) and a Tennessee business license.

Property owners can sometimes pull their own permit for a residence they will use personally — not for resale, lease, or rent — subject to state homeowner-permit limits (commonly once every 24 months). City and county homeowner guidance both lean that way.

If the ADU will be a long-term rental, assume you need a licensed contractor on the permit. with LDO or County Building Inspections before choosing an owner-builder path you later outgrow.

Building a new main house and an ADU together requires separate permits for each unit.

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Garage Conversion vs New Detached: What Changes on the Permit

Garage conversion path — plan for parking replacement on the site plan if you lose a stall serving the main house.

New detached path — setbacks, height, rear/side yard placement, and utilities drive the permit package.

Both paths are ADUs. The paperwork emphasis shifts.

Topic	Garage conversion	New detached backyard unit
Zoning story	Prove ADU size/location rules + habitable-space code	Prove setbacks, height, rear/side yard placement
Parking	Almost always replace lost main-house parking on the site plan	No ADU parking minimum; still show main-house parking
Structure	Framing, insulation, ceiling height, fire separation, existing slab	Full foundation; slope/drainage often drives engineering
MEP	Bath/kitchen runs, panel capacity, HVAC for conditioned space	New EPB path; new water/sewer laterals as needed
Egress	Code windows/doors; 701–800 sq ft needs two exits	Same rules; easier to design in from day one
Common delay	Drawings that skip habitable-space details	Incomplete utilities or height measured wrong

For conversion scope, see our garage conversion overview. Attached family suites: mother-in-law suite construction — the checklist above still governs the permit gate.

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What Kills Applications or Burns Weeks

Most “the city is slow” stories are incomplete packages. Patterns we see:

Problem	Why review stalls
Over 800 sq ft exterior	Conditioned loft or stairwell quietly pushed past the cap
Missing parking replacement	Garage conversion removed a stall serving the main house
Front-yard detached pad	Detached ADUs belong in rear or side yard
Height measured wrong	Detached height uses the zoning definition; street-side measurement matters
Thin site plan	No setbacks, unlabeled structures, no utilities, no parking
HOA ignored	Zoning can approve while the association still says no
Historic district skipped	Needs Certificate of Appropriateness in addition to the building permit
Septic assumption (county)	If resolution text is in force, individual septic kills the ADU path
Owner-occupancy missed (county)	Resolution text requires the owner in one of the two units
STR design first	Short-term rules are separate — and often stricter than long-term rental
Tiny home on wheels	Not an ADU pathway; permanent foundation required
Under-documented conversion	Insulation, egress, ceiling height, and MEP not addressed as habitable space
Wrong jurisdiction	City drawings submitted to county (or the reverse)

Attached basement units hit the same trap: already under the roof does not skip ADU rules if the space has independent cooking, sleeping, and bathing.

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Honest Timeline Bands (Not Promises)

Construction timelines stretch for site work, utilities, and weather — not just the plan-review calendar.

There is no official ADU clock. Plan around ranges:

Stage	Typical timing	Caveat
Pre-submittal meeting	Schedule into a Tue/Thu morning slot (city)	County intake differs — ask staff
Plan review after complete submittal	Often 5–10 business days (city CHCRPA guidance)	Volume and revisions stretch this
Inspection scheduling	Often next business day; busy times 48+ hours	Request in the portal early
Construction — garage conversion	Roughly 3–5 months	Local project experience, not a city SLA
Construction — new detached	Roughly 5–8 months	Slopes, utilities, and weather dominate

Slopes, utility extensions, historic review, and incomplete drawings add weeks more often than surprise permit-line fees. Permit and review costs commonly sit in the low thousands before design, engineering, and utility taps — the live fee schedule on the city’s residential building permit page.

For budget context after the permit path is clear, see the 2026 ADU cost post.

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Rental Intent Belongs in the Permit Conversation Early

Long-term rentals (more than 30 days) in the city generally do not need a special city rental permit unless your HOA restricts rentals.

Short-term vacation rentals are different. In the city, an STR certificate is required, and absentee STRs are limited to certain commercial and mixed-use zones. A residential backyard ADU usually fits family use or a conventional long-term tenant better than an Airbnb-first plan.

In unincorporated Hamilton County, resolution text prohibits using the ADU as a short-term vacation rental. current STR rules before you design around vacation income. One home occupation is allowed per lot — in either unit, not both.

If you pull as a homeowner for personal use and then immediately lease the unit, you may be outside what state and local offices allow. Ask before you choose that path.

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Walk the Lot Before You Book the Meeting

Walk the lot before you book the pre-submittal meeting — a clean package starts on the ground.

A clean ADU permit package starts with an honest read of the ground: city versus county, setbacks, height, parking replacement, sewer versus septic, slope, HOA, and historic overlays. Peaceful Haven Homes walks Chattanooga and Hamilton County properties with that checklist in mind, then designs and builds garage conversions and detached backyard units that can clear review.

Call or text (423) 777-6849, use our contact page, or start your project before you book the Land Development Office meeting. We will help you choose conversion versus new build, map the permitting steps, and keep drawings aligned with what reviewers will approve.Always verify current requirements, fees, portal labels, and forms with the Land Development Office (city) or Building Inspections (county) before design or construction. HOA documents and historic-district guidelines can be stricter than zoning.*

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