Home addition permits in Southeast Michigan
Every addition in Michigan needs a building permit, and most need zoning approval before the building permit is even reviewable. Those are two separate reviews run by two different desks, and homeowners routinely discover the second one late. Zoning decides whether you may build the thing at all. The building permit decides whether what you drew meets code. Getting them in the right order saves weeks.
Wright’s Renovations pulls permits in Washtenaw, Wayne, Oakland, Macomb, Livingston and Monroe counties, which means dealing with several dozen building departments that share a state code and share almost nothing else. This page explains what the process actually looks like, what it costs, and where projects in this region get stopped.
What needs a permit
Any addition, any structural change, any new plumbing or electrical circuit, most window openings cut into a foundation wall, decks above a certain height, and finishing a basement into habitable rooms. Michigan works from the Michigan Residential Code, so the technical requirements are consistent statewide even where the paperwork is not.
- Building permit for the structure, framing and envelope.
- Separate mechanical, electrical and plumbing permits, usually pulled by the licensed trades.
- Zoning approval or a site plan review, depending on the community.
- County health approval where the property is on a well or septic system.
- Historic district review where the property sits inside one.
Work under a few hundred dollars in value and cosmetic work such as paint, flooring and cabinet replacement generally do not. When there is doubt, the building department will answer the question over the phone in five minutes, and that call is free.
Zoning comes first, and it decides more than you expect
Setbacks, height and lot coverage
Zoning tells you how close a structure may sit to each lot line, how tall it may be, and what percentage of your lot may be covered by buildings. Those three numbers frequently shrink an addition before design starts, particularly on the narrow lots common in older Ann Arbor and Ypsilanti neighborhoods where houses were built before current setbacks existed.
An existing house that sits closer to a lot line than today’s rules allow is legally nonconforming, which is fine until you try to extend along that same wall. We check the zoning text and the property survey during feasibility rather than after drawings exist, because a redesign at permit review is expensive and demoralizing. The design-build process page shows where that check sits in the sequence.
When you need a variance
If the design cannot meet the rules, you can request a variance from a zoning board of appeals. That means a public hearing, notice to neighbors, a written finding of practical difficulty, and a wait of one to three months. Variances are granted often enough to be worth pursuing and rarely enough that no responsible builder will promise you one. Budget the time and have a fallback design.
The fallback is often a smaller footprint rather than a different location. A bump-out that stays inside the setback line gets built this year, while a full wing that needs a variance may or may not get built at all. On constrained lots that tradeoff is worth having on the table early, alongside the option of building up rather than out or finishing space you already own.
Accessory dwelling units, where the rules diverge
Michigan has no statewide accessory dwelling unit law, so a second dwelling on a single-family lot is permitted or prohibited entirely by local ordinance. Within our service area only a handful of communities clearly allow one, which is the single most important fact for any family planning a rentable suite. Our accessory dwelling unit page covers construction detail.
The Ann Arbor rules
Ann Arbor permits one accessory dwelling unit per single-family detached dwelling in its R1 through R4 districts. Size is capped at 600 square feet on lots up to 7,199 square feet and 800 square feet on larger lots, or the ground floor area of the main house, whichever is less. Detached units cap at 21 feet tall, attached at 30 feet, and no unit may sit within the required front setback or closer than three feet to a lot line.
Occupancy is limited to two people plus offspring in the unit, with a combined cap across both dwellings. Leases shorter than 30 days are prohibited, so a suite can be a long term rental and cannot be a short term one. There is no public hearing or site plan requirement, which makes Ann Arbor one of the more workable communities in the region for this kind of project. Local context is on our Ann Arbor page.
Other communities and the state bill
Chelsea, Dexter, Ferndale and Berkley have each adopted accessory dwelling provisions with their own limits, and some of that language is recent enough that it is worth confirming the current text with the community development office. Several other communities in the six counties do not permit a second dwelling at all, and Detroit had not adopted its drafted ordinance as of the spring of 2026.
Legislation limiting local restrictions on accessory dwelling units was introduced in the Michigan House in February of 2026. It has not passed either chamber, sits in committee, and has lost cosponsors since introduction. Design for the ordinance your community has today. If it changes, an attached suite converts far more easily than a stalled project restarts. The in-law suite page covers the attached path that works nearly everywhere.
What the review looks like by project type
Different projects trip different reviews, and knowing which ones apply tells you how long the front of your schedule really is. The pattern below holds across most communities in the six counties, though the names of the desks and the number of copies they want will vary.
- A detached garage is mostly a zoning review, since setbacks, height and lot coverage do the deciding.
- A second story addition adds structural review, because the existing foundation and framing have to carry the new load.
- A deck is a straightforward building permit with footing and final inspections, and it is one of the most commonly skipped permits in the region.
- A basement dwelling unit triggers zoning, egress, ceiling height and mechanical review together.
- A sunroom depends on whether it is conditioned, since a heated room is habitable space and a three-season room is not.
Accessibility work sits in its own category. Grab bars and hardware need nothing. Widening a load bearing opening, relocating plumbing for a curbless shower, or building a main floor bathroom all need permits, and our accessibility modifications page explains which items cross that line.
What permits cost and how long they take
Permit fees are usually calculated on project valuation, so an addition typically runs several hundred to a few thousand dollars in combined building, mechanical, electrical and plumbing fees. A detached garage commonly lands around $1,200 to $2,000. Plan review and zoning fees are separate, and some communities charge for the escrow that funds their consulting reviewer.
Timing varies more than cost. A straightforward addition in a well staffed department can be reviewed in two to four weeks. A community using an outside plan reviewer, or one with a site plan requirement, can take six to twelve. Add a month or more for anything needing a variance or historic review. Our addition timeline builds those windows into the schedule rather than treating them as delays.
The inspections you will actually see
Inspections happen at fixed points and construction stops until each passes. Footing inspection before concrete. Foundation and backfill. Rough framing, rough electrical, rough plumbing and rough mechanical, usually together once the shell is weather tight. Insulation before drywall. Then final inspections in each trade and a certificate of occupancy where one applies.
The rough stage is where problems surface, and it is the reason a builder who prefers to close walls quickly is a builder to avoid. If something is wrong, the cheapest moment to find it is while it is still visible. This is also where code items such as egress openings get verified against the requirement of at least five square feet of clear opening at grade level with a sill no higher than 44 inches.
Septic, wells and the county health review
Any property outside a municipal sewer district adds a health department review, and it is often the longest item on the front of the schedule. Adding bedrooms increases the design load on a septic system, and a drainfield sized for three bedrooms may not support five. In Washtenaw County that evaluation should start at the very beginning of design, because the answer can change the floor plan.
Wells add isolation distance requirements between the well, the septic components and any new structure. Those distances are fixed, they are enforced, and they can rule out an addition in the location you wanted while permitting it fifteen feet away. Finding that out during design costs nothing. Finding it out after drawings costs a redesign.
Historic districts and older neighborhoods
Several communities in this region maintain local historic districts, Ann Arbor among them, where exterior changes require review before a building permit issues. That review looks at massing, materials, window patterns and how visible the addition is from the street. It is not a prohibition on building, and successful projects in these districts usually put the addition at the rear and match the existing detailing rather than contrasting with it.
Older houses carry code implications beyond the historic review. Knob and tube wiring, undersized services and framing that predates modern spans all surface once walls open. Our historic home renovation pages describe how we approach that work, and the craftsman and colonial pages get specific by style.
What happens when work is done without a permit
Three things, usually years later. The municipality can require the work be opened for inspection or removed. Your insurer can decline a claim tied to unpermitted work. And the sale of the house stalls when a buyer’s inspector or title company finds square footage the assessor has never seen.
Unpermitted additions are common in this region and they are fixable, though the retroactive path is slower and more expensive than doing it correctly. If you bought a house with a finished basement or a sunroom of uncertain provenance, it is worth checking the permit record before you build anything else, because the new permit application is exactly when the old work comes up.
Who pulls the permit, and why it matters
Michigan requires a licensed residential builder for work above a modest dollar threshold, and the builder normally pulls the permit and carries responsibility for the inspection sequence. Homeowners can pull their own permit on their own residence in many communities, and it shifts liability onto them for the code compliance of everything on the site.
A contractor who asks you to pull the permit for work they are performing is asking you to take their liability. It is a legitimate arrangement in a few narrow situations and a warning sign in most. We pull our own, schedule our own inspections and are on site for them, which is described further on our estimate and consultation page.
Questions homeowners ask
Can we start while the permit is pending? No, and doing so risks a stop work order plus a penalty fee in most communities. Demolition sometimes proceeds on a separate permit. The productive use of that waiting period is finishing selections, which keeps the finish schedule from becoming the delay after construction begins. The cost calculator is a reasonable place to pressure test the budget while you wait.
Does a permit raise my property taxes? Improvements are added to taxable value in Michigan outside the annual cap, so a substantial addition will raise your bill. That is true whether or not you permit the work; the difference is that permitted work is assessed correctly and unpermitted work becomes a problem at sale. Cost context is on our addition cost guide.
Do we need a permit to finish a basement? Yes, for the framing, electrical, plumbing and mechanical work, and for any bedroom’s egress opening. Basement projects fail inspection most often over egress and ceiling height, both of which are worth confirming before design. See our basement permits guide.
Let us handle the paperwork
Permitting is the part of a project homeowners least want to own, and it is the part where local knowledge saves the most time. We know which departments want what, and we build the review windows into the schedule from the start. We work across all six counties from 7101 Platt Road in Ypsilanti. View our Portfolio or contact us now for a free quote. The office line is (734) 540-0347.
