What a Garage Conversion ADU in Three Oaks Actually Costs and How Long It Takes
A garage conversion ADU in Three Oaks typically runs between $30,000 and $80,000, with most jobs landing in the $45,000-$65,000 range for a fully permitted, move-in-ready unit. The work usually takes 8-14 weeks from demo to final inspection, depending on whether you’re adding a bathroom where there wasn’t one before. Call (844) 638-7249 to get a written, line-item estimate for your specific garage - it’s free and there’s no obligation.
We build these projects as part of a full Home Additions & ADU in Three Oaks scope, which means the permitting, structural engineering, and finish work all run through one crew without subcontractor gaps. A garage conversion is the most cost-efficient ADU path you can take because the foundation, roof, and three of the four walls already exist. The job is about bringing the inside of that shell up to residential code and making it feel like it was always part of the house, not a dressed-up parking spot.
How We Convert a Garage - The Real Stage-by-Stage Sequence
The process is straightforward, but every homeowner who’s been through a major renovation will tell you the same thing: knowing what happens and when is what keeps the stress down. Here’s exactly how it goes from our side.
Stage 1 - Engineering, Permits, and Pre-Construction (Weeks 1-3). We start with a site visit to measure the existing slab, check the roof structure, and map where utilities can tie in. Lee County’s post-Ian permitting environment means the building department is going to look hard at wind-load paths and flood-plain compliance, so we bring in a structural engineer early if the garage wasn’t originally built with hurricane straps. Most Three Oaks garages from the 1990s and early 2000s weren’t, and that’s the single biggest scope variable on these jobs. You’ll pick your floor plan layout during this phase - where the kitchenette lands, whether the bathroom goes against the existing wet wall or requires a new sewer tie-in - and we’ll give you a fixed price before permits go in.
Stage 2 - Demo, Slab Prep, and Rough-In (Weeks 3-5). The garage door comes out and gets framed into a standard exterior wall with a window or French doors, depending on what the plan calls for. We cut the slab where new plumbing needs to run, trench to the main sewer line, and rough in all supply lines, drains, and electrical. If the existing slab isn’t level - common in older Lee County block homes where soil settlement has done its thing over 20-30 years - we’ll pour a thin self-leveling overlay so the finished floor sits flat. Insulation goes into the walls and ceiling at this stage, and we run any new HVAC ducting or mini-split line sets.
Stage 3 - Drywall, Mechanicals, and Exterior Tie-In (Weeks 5-8). Once the rough-in passes inspection, we hang and finish drywall, set the electrical panel if the ADU needs its own sub-panel, and install the mini-split or tie into your existing central system. The exterior gets matched to the main house - same stucco texture, same paint, same trim style - so it reads as original square footage, not an afterthought. This is when homeowners often ask us about upgrading the driveway or patio area at the same time, and our Home Additions & ADU crew can coordinate that so you’re not tearing things up twice.
Stage 4 - Finishes and Fixtures (Weeks 8-11). Flooring, cabinets, countertops, tile, trim, paint, and plumbing fixtures all go in. We’re installing the same-grade materials here that we’d put in a primary residence kitchen or bath because a rental unit or mother-in-law suite needs to hold up to daily use and Florida humidity. This is the stage where clients walk in and see it as a real living space for the first time. We do a punch-list walkthrough with you before final inspection so nothing gets missed.
Stage 5 - Final Inspection and Handoff (Weeks 11-14). Lee County inspects structural, electrical, plumbing, and mechanical. Once we have the green tag, we clean the site, walk you through every system in the unit, and hand over the warranty paperwork. Our 730-Day Done Right Promise covers the work for two full years - if something isn’t right, we fix it.
The Decisions You’ll Make on Materials and Layout
You’re not picking from an endless catalog here. The choices that actually matter on a garage conversion come down to a handful of categories, and each one has a real trade-off between cost, durability, and how the space feels.
- Flooring: luxury vinyl plank vs. tile. LVP is warmer underfoot, costs less to install over a slab, and handles minor slab imperfections without cracking. Tile - especially a large-format porcelain - holds up better against sand and moisture tracked in from a Three Oaks driveway and stays cooler in summer. Most ADUs we build here use tile in the bathroom and LVP everywhere else.
- Kitchenette: wet bar vs. full galley kitchen. A wet bar with a sink, undercounter fridge, and microwave is the budget-friendly route and doesn’t require a ventilation hood or 220V range line. A full galley kitchen with a cooktop, oven, and vent hood adds $4,000-$8,000 to the electrical and mechanical scope but makes the unit fully independent - important if you’re renting it out. For cabinets, we spec KraftMaid or equivalent semi-custom lines so the sizing fits the typically smaller ADU footprint without filler strips everywhere.
- Bathroom: shower only vs. tub-shower combo. A walk-in shower with a glass enclosure takes less floor space and works better for aging-in-place use. If the ADU is for a small family or you want resale flexibility, a tub-shower combo adds about $1,500-$2,500 to the plumbing and finish scope. Our Backsplash, Tile & Flooring in Three Oaks work often dovetails here - we can continue the same tile package through the kitchenette and bath for visual continuity.
- Climate control: mini-split vs. central HVAC tie-in. A ductless mini-split runs $2,500-$4,500 installed and gives you zoned heating and cooling independent of the main house. Tapping into the existing central system costs less upfront - about $1,200-$2,000 - but you’re sharing thermostat control and air-handler capacity, which matters if the main system was sized tight to begin with.
- Exterior wall: matching the house vs. a new opening. Replacing the garage door with a matched stucco wall and a standard window is the cleanest look and costs less than framing in French doors or a sliding glass door. If the ADU opens onto a patio or backyard, however, glass doors make the unit feel twice as large. We install impact-rated Andersen or Pella doors here - anything less won’t pass Lee County wind-mitigation review.
What a Garage Conversion ADU Costs in Three Oaks, FL
A basic garage conversion ADU in Three Oaks - one bedroom, one bathroom, kitchenette, no major structural changes - starts around $30,000. A high-end conversion with a full kitchen, custom bath, separate HVAC, new sewer line, and impact-rated doors can reach $80,000. Most of the jobs we price in this area fall between $45,000 and $65,000.
What pushes a project toward the low end: the garage slab is level and in good condition, the existing roofline ties into the house cleanly, the bathroom can share a wet wall with the main house plumbing, and you’re keeping the electrical panel where it is. What pushes it toward the high end: you need a new sewer lateral trenched in, the roof trusses require hurricane-strap retrofitting, the slab needs significant leveling or a moisture barrier, and you’re adding a full kitchen that demands a sub-panel, ventilation, and a gas line or 220V circuit.
We give you a written, line-item estimate before any money changes hands. That estimate includes all materials, labor, permits, and engineering. It does not include things some contractors leave as “allowances” and then change-order later - our pricing is upfront and fixed. No surprises. You’ll also see a separate line for any optional scope, like upgrading the driveway pavers to match the new entrance, so you can decide what’s worth it now versus later. We’ve had homeowners pair this work with Cabinets & Countertops in Three Oaks upgrades in the main house at the same time, which lets us run both scopes under one permit and one crew.
What Three Oaks Homes Specifically Do to This Job
Three Oaks sits in Lee County, which absorbed the full force of Hurricane Ian in 2022 - a storm that rewrote the construction rulebook here. The practical effect on a garage conversion is that almost every job we open up needs structural remediation before we can do anything cosmetic. Most of the concrete-block homes in this neighborhood were built between 1990 and 2005, and a large share of them had no hurricane straps connecting the roof trusses to the block walls. The county won’t sign off on converting that garage to living space until the entire roof-to-wall connection is brought to current Florida Building Code 2023 standards, which means engineered anchor retrofits and continuous load-path hardware. That adds anywhere from $3,000 to $7,000 to a project that, in an inland market, would have been a straight interior build-out.
The other local reality is moisture. Southwest Florida’s humidity doesn’t take a day off, and a garage slab that was poured as a parking surface often lacks the under-slab vapor barrier that finished living space requires. We test for that early. If moisture is migrating up through the concrete - and it often is in homes around the Cypress Lake Drive corridor and older sections near Three Oaks Parkway - we install a full vapor barrier and sometimes a dimple mat before flooring goes down. This isn’t something you’d think about until the LVP starts cupping six months later, but we’ve seen it enough times to check it on every job. Our team covers all of Three Oaks and knows which blocks tend to have wet slabs and which don’t, just from doing this work in the neighborhood for years.
Serving Three Oaks, FL - Our Local Coverage Area
We’re based in the Three Oaks area and know this community well. Use the map below to see our service coverage - if you’re nearby, we can almost certainly help.
Frequently Asked - Garage Conversion ADU in Three Oaks
Yes. Lee County requires a full building permit for any garage conversion that adds living space, and the plans must be stamped by a Florida-licensed structural engineer. The county will inspect structural, electrical, plumbing, and mechanical work at multiple stages. Skipping permits isn’t just a code violation - it creates a liability problem when you sell the house because the square footage won’t match county records. We pull every permit and handle the inspections from start to finish.
Plan on 8 to 14 weeks from the day we start demo. The biggest variable is whether the trusses need hurricane-strap retrofitting, which adds about a week to the structural phase. Permitting in Lee County is running faster now than it was in the immediate post-Ian backlog, but you should still budget 2-3 weeks for plan review before we can start work.
You can, if you’re fine with the ADU not having a bathroom or kitchen. Practically speaking, a habitable ADU needs at least a bathroom, and that means running a sewer line from the new bathroom location to the main house drain. If the garage shares a wall with an existing bathroom or kitchen, we can often tie into that wet wall and keep costs down. If the garage is detached or on the opposite side of the house, you’re looking at trenching for a new sewer lateral - which is a $4,000-$9,000 line item depending on distance and soil conditions.
A permitted ADU in Three Oaks typically adds 60-80% of its construction cost to the home’s appraised value, but the real return is in rental income. A one-bedroom ADU in this part of Lee County rents for $1,200-$1,800 a month in the current market. On a $55,000 conversion, that’s a 2-3 year payback period before factoring in property value appreciation. This is the math most of our clients are running, especially with post-Ian housing demand still elevated in the Fort Myers metro area.
Every garage conversion ADU we build is covered by our 730-Day Done Right Promise - two full years of workmanship coverage. If anything isn’t right, we make it right, no fine print and no pushback. That’s one of the longest guarantees you’ll find in residential construction, and it’s backed in writing. Material warranties from manufacturers like KraftMaid, Kohler, and Andersen cover their products separately, often for considerably longer, and we’ll walk you through exactly what’s covered under each one at handoff.
Get a Free, Written Estimate for Your Garage Conversion in Three Oaks
If you’re looking at your garage and wondering what it would take to turn it into a real living space, call (844) 638-7249. We’ll come out to your home in Three Oaks, walk the space with you, and give you a fixed-price estimate that breaks down every line item - materials, labor, permits, engineering - so you know exactly what the number is and why. Estimates are free, and you’re never under any pressure to sign. Derek Hollenbeck leads our team, and we make sure every call gets answered by a live person, 24/7. No voicemail, no waiting.
Written by Derek Hollenbeck, Owner at Groundwork Construction Co., serving homeowners across Lee County with upfront pricing and a 730-Day Done Right Promise.