Garage Conversion ADU in Westchester - What’s Involved, What It Costs, and How Long It Takes
A garage conversion ADU in Westchester transforms an existing attached or detached garage into a permitted, habitable living unit with its own kitchenette, bathroom, sleeping area, and separate entrance. Most projects we handle in the 33144 area run 4 to 6 months from permit submission to final inspection, with construction itself taking 10 to 14 weeks. Expect to invest between $30,000 and $80,000 depending on whether your garage already has power and plumbing rough-ins or we’re starting from bare concrete and a roof that needs structural upgrades. Call (844) 665-0162 and we’ll walk your specific space this week - estimates are free.
How We Turn a Westchester Garage Into a Legal ADU
We’ve refined this into five clear stages. You’ll know what’s happening, what you’re deciding, and roughly when.
Stage 1: Site evaluation and feasibility (Week 1)
We visit your property, measure the garage footprint, photograph the existing slab, roof structure, electrical panel, and any plumbing access. You’ll decide right then whether you want a full ADU with kitchen and bath, or a simpler studio without cooking facilities - that choice changes the permit path and the budget by $8,000-$15,000. We also flag early if your garage shares a roofline with the main house that needs HVHZ-compliant re-decking, which is common on 1960s-era CBS ranches near Westchester’s interior streets.
Stage 2: Design and permit docs (Weeks 2-6)
Our draftsperson produces plans showing the new layout, egress window placement, electrical load calculations, and tie-ins to existing sewer or septic. You’ll choose your material tier here - flooring, cabinetry, fixtures - because those specs get written into the permit set. Miami-Dade County’s unincorporated permitting office reviews ADU conversions as “accessory dwelling unit” applications, not simple remodels, so expect 3 to 5 weeks for plan review. We handle the NOA product certifications and wind-load calculations that HVHZ demands.
Stage 3: Demolition and rough construction (Weeks 7-10)
The garage door comes out, the opening gets framed and sheathed to match the house, and we cut in any new windows required for light and egress. If we’re relocating the electrical panel or adding a sub-panel, that happens now. You’ll make your final cabinet and countertop selections during this window - we typically spec KraftMaid or Wellborn for Westchester garage ADUs, with Silestone or Caesarstone for the compact kitchenette surfaces.
Stage 4: Mechanicals, insulation, and finishes (Weeks 11-16)
HVAC gets routed - usually a mini-split system since the load is small - followed by insulation, drywall, flooring, and fixture installation. Plumbing rough-in for the bathroom and kitchenette gets pressure-tested before walls close. This is where homeowners often ask us about pairing the interior with Cabinets & Countertops in Westchester for the main house kitchen, or Backsplash, Tile & Flooring in Westchester to keep material continuity across the property.
Stage 5: Inspections and final walkthrough (Weeks 17-20)
Miami-Dade requires rough electrical, rough plumbing, insulation, and final inspections for ADU conversions. We schedule them sequentially and attend each one. You’ll do the final walkthrough with Raymond Estevez, checking fixture operation, paint touch-ups, and that the separate entrance locks and seals properly.
The Choices That Shape Your Garage Conversion ADU
Every decision below moves your number and your daily experience. We lay out the honest trade-offs:
- Full kitchenette vs. kitchenette waiver: A complete cooking setup with range, vent hood, and cabinets adds $6,000-$12,000 but makes the unit rentable at market rate. A waiver - permitted as “efficiency” with just a microwave and mini-fridge - saves money but limits tenant appeal and may affect appraisal.
- Wet bath vs. full bath: A wet bath (shower open to the room, drain in the floor) fits in 25 square feet and costs $3,500-$6,000. A full bath with shower enclosure, vanity, and water closet needs 35-40 square feet and runs $5,500-$10,000. For 400-square-foot garage ADUs in Westchester, the wet bath often wins on space economics.
- Mini-split HVAC vs. extending central: A dedicated mini-split ($2,500-$4,500 installed) gives the tenant independent climate control. Tapping your main house system risks overload on original 100-amp panels common in 1960s Westchester homes and creates billing disputes.
- Slab-on-grade vs. raised floor: Many Westchester garages sit slightly below the main house slab. We can pour a leveler and moisture barrier ($1,500-$3,000) or build a raised wood subfloor with insulation ($3,500-$6,000). The raised floor feels warmer and allows plumbing drain lines to run above grade, but steals 4-6 inches of headroom.
- Standard fixtures vs. upgraded: Kohler and Moen mid-grade lines hold up well in rental ADUs without the replacement anxiety of bargain brands. We typically spec these for Westchester conversions unless the homeowner is aging-in-place and wants grab bars, comfort-height toilets, and lever handles throughout.
What Garage Conversion ADU Costs in Westchester, FL
| Component | Low Range | High Range |
|---|---|---|
| Basic garage conversion (studio, no kitchen) | $30,000 | $45,000 |
| Mid-grade ADU with kitchenette and bath | $45,000 | $65,000 |
| Full ADU with upgraded finishes, separate meter | $65,000 | $80,000 |
Five variables push you up or down this range. Existing condition is the biggest - a garage with a cracked slab, failing roof, or no electrical service adds $8,000-$20,000 before we build anything new. Plumbing relocation matters enormously; if your main sewer line sits on the opposite side of the house, we’re trenching across the yard or pumping uphill. Structural changes - widening the garage door opening into a proper entry, or sistering rafters for a new roof load - run $3,000-$10,000. Material grade moves the finish budget by 30-50 percent, especially cabinets and countertops. And permit scope in unincorporated Miami-Dade means HVHZ compliance, NOA products, and sometimes flood-zone elevation certificates that add $1,500-$4,000 in fees and engineering.
A written estimate from us includes demolition, framing, rough and finish electrical, plumbing, HVAC, insulation, drywall, flooring, fixtures, paint, and permit fees. It does not include separate meter installation from FPL, landscaping repair, or any main house work you decide to add mid-project.
What Westchester Homes Specifically Do to This Job
Westchester sits in unincorporated Miami-Dade County within the High Velocity Hurricane Zone, which means every garage conversion ADU must use products carrying a Miami-Dade Notice of Acceptance and pass wind-load inspections that contractors in incorporated cities like Coral Gables don’t face in identical form. The county permitting office, not any city hall, reviews your plans - and they’re thorough about egress windows, roof tie-downs, and whether your garage roof can handle the new ceiling load of insulation and drywall.
The housing stock matters too. Most garages we’re converting in the 33144 ZIP were poured in the 1950s-1970s alongside single-story CBS ranch homes, with slabs that may have settled, original electrical panels that won’t carry a second kitchen, and flat roofs that have been re-covered two or three times. Current HVHZ code mandates tear-off to the deck before any new roofing system gets approved, so a garage conversion often triggers a full roof inspection that reveals rotted nailers or insufficient fastening. We’ve learned to budget for this possibility on every Westchester garage project rather than surprise homeowners mid-build.
The wet season shapes scheduling. From June through September, afternoon thunderstorms halt exterior work and slow deliveries. We typically rough-frame and roof in the drier months, then move inside for finishes during summer - planning the permit timeline around weather, not just calendar convenience.
Serving Westchester, FL - Our Local Coverage Area
We’re based in the Westchester 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 Westchester
Most projects take 4 to 6 months from permit submission to final certificate of occupancy, with actual construction lasting 10 to 14 weeks. Miami-Dade’s plan review for ADU conversions typically adds 3 to 5 weeks that simpler remodels don’t require. Call (844) 665-0162 and we’ll review your specific garage’s condition - some are faster, some need structural work that extends the timeline.
Yes, and it’s not optional. Because Westchester is unincorporated Miami-Dade County, your project falls under county building codes, HVHZ wind-load requirements, and Miami-Dade’s ADU zoning rules. We handle the full permit package, including NOA product certifications and engineered drawings. Attempting this without permits risks stop-work orders, fines, and an uninsurable, unrentable unit.
Sometimes, but rarely completely. Most Westchester garages have power for a door opener and a few outlets - inadequate for a kitchenette, bathroom, and HVAC. Plumbing almost always needs extension from the main house, especially if your garage sits on the opposite side from the sewer line. During our free evaluation, we map your existing utilities and show you exactly what relocation involves before you commit.
A garage conversion ADU in Westchester typically runs $30,000-$80,000, while a new detached ADU starts around $90,000 and often exceeds $150,000. You’re leveraging existing walls, roof, and slab rather than building from dirt. The savings disappear if your garage needs extensive structural repair, but most conversions still land well below new construction.
Groundwork Construction Co. warranties our workmanship on garage conversion ADUs, and the products we install carry their own manufacturer warranties - Kohler fixtures, KraftMaid cabinetry, and Silestone or Caesarstone surfaces each have specific coverage terms we’ll document for you. We also ensure all work passes Miami-Dade final inspection, which is your strongest long-term protection. For exact warranty language on your project, call (844) 665-0162 and Raymond Estevez will walk through it with you.
Get a Free On-Site Estimate for Your Westchester Garage Conversion
We’ll visit your property, measure the garage, check your existing slab and utilities, and give you a written estimate with real numbers - no pressure, no deposit required to start the conversation. Call (844) 665-0162 to schedule. Raymond Estevez handles the initial walkthrough personally, and we’ll have a permit-ready scope and timeline back to you within a week.
Written by Raymond Estevez, Owner at Groundwork Construction Co., serving Westchester and South Florida. For the full picture of how a garage conversion ADU fits into a larger home expansion, see our Home Additions & ADU in Westchester page, or explore everything our Home Additions & ADU crew handles across the region.