How Much Does Junior ADU & Interior Conversion Cost in Hobe Sound?
Junior ADU & Interior Conversion in Hobe Sound typically runs $45,000-$130,000 and takes 8-14 weeks from permit to final inspection. This job transforms an existing portion of your home - usually a primary bedroom suite, attached garage, or underutilized wing - into a self-contained living unit with its own kitchenette, bathroom, sleeping area, and separate exterior entrance. Call (844) 665-0162 for a free on-site estimate and we’ll walk your specific layout.
The Way We Build a Junior ADU & Interior Conversion - Start to Finish
We’ve done enough of these in Martin County to know where the friction points hide. Here’s the actual sequence, with what you’re deciding at each stage.
Stage 1: Feasibility and zoning check (Week 1)
We pull your property’s Martin County zoning classification and verify setbacks against the Coastal Construction Control Line if you’re east of U.S. 1 or near the Intracoastal. For homes in the 33455 mainland area, we’re checking whether your lot allows a second dwelling unit under the county’s growth management rules. You’ll decide whether to proceed with a full Junior ADU & Interior Conversion or scale back to an accessory living space without a separate kitchen. This stage costs nothing - it’s part of our initial walkthrough.
Stage 2: Design and permit drawings (Weeks 2-4)
Our draftsman produces plans showing the new partition walls, the relocated or extended plumbing rough-ins, the electrical subpanel or service upgrade, and the new exterior door location. In Hobe Sound, Martin County requires engineered drawings for any structural modification to exterior walls, which most Junior ADU & Interior Conversions trigger when we cut in that separate entrance. You’ll choose your kitchenette footprint here - a wet bar with mini-fridge and induction cooktop, or a full compact kitchen with gas or electric range. That decision drives your plumbing scope and your permit path.
Stage 3: Demolition and rough construction (Weeks 5-8)
We frame new interior partitions, rough in the bathroom and kitchenette plumbing, run dedicated electrical circuits for the subpanel, and cut the new exterior door opening. If your home dates from the 1960s-1980s ranch era common in mainland Hobe Sound, we’re almost always upgrading the electrical service and adding hurricane straps or tie-downs that weren’t original. You’ll make your material selections during this window - flooring, cabinets, countertops, fixtures - so we can order with lead times in mind.
Stage 4: Systems, insulation, and envelope (Weeks 9-11)
Insulation goes in, drywall goes up, the mini-split HVAC gets mounted and charged, and we finish the exterior door with proper flashing and sealant. For properties near the water in Hobe Sound, we spec impact-rated door assemblies and corrosion-resistant fasteners - experience we’ve honed through Hobe Sound Roof Repair work - the salt air here eats standard hardware within a few years. You’ll do a mid-stage walkthrough to confirm outlet locations, lighting switches, and any smart-home rough-ins you want.
Stage 5: Finish work and final inspection (Weeks 12-14)
Cabinets, countertops, flooring, tile, fixtures, paint, and trim. Martin County building inspectors verify the separate entrance, the egress window in the sleeping area, the kitchenette ventilation, and the electrical subpanel labeling. We schedule the final, make any punch-list corrections, and hand you the certificate of occupancy. You’re deciding on paint touch-ups and whether to add a small patio or walkway outside that new door - something we often pair with our Home Additions & ADU services.
The Choices That Shape Your Junior ADU & Interior Conversion
- Kitchenette scope: A wet bar with under-counter fridge and microwave drawer runs $3,500-$7,000 installed. A full compact kitchen with range, dishwasher, and apartment-size refrigerator runs $8,000-$15,000. The wet bar keeps you under Martin County’s threshold for a full “dwelling unit” in some zoning districts, which can simplify permitting. The full kitchen makes the space genuinely rentable or comfortable for long-term family use.
- Bathroom configuration: A three-piece bath with shower-tub combo fits in 35 square feet and costs $6,000-$12,000. A walk-in shower with glass enclosure needs 40+ square feet and runs $8,000-$15,000. In older Hobe Sound homes with 3-inch cast-iron drains, the walk-in shower often requires a drain line upgrade to 4-inch PVC - add $1,500-$3,000.
- Flooring: Luxury vinyl plank ($4-$8/sq ft installed) handles humidity well and installs fast. Tile ($7-$14/sq ft) lasts longer but needs a stiffer subfloor, which we sometimes find lacking in 1970s slab construction. Engineered hardwood ($6-$12/sq ft) looks sharp but needs careful moisture management this close to the Atlantic.
- HVAC approach: A dedicated mini-split ($3,000-$5,500) gives the Junior ADU & Interior Conversion its own thermostat and doesn’t load your main system. Extending ductwork from your existing central unit costs less upfront ($1,500-$3,500) but often struggles to balance temperatures across a now-partitioned home.
- Exterior door and entry: A standard steel prehung with sidelight runs $1,200-$2,500. An impact-rated fiberglass door with transom, required for coastal exposure zones in Hobe Sound, runs $2,800-$5,500. The impact rating isn’t optional if you’re within the Martin County wind-borne debris region.
What Junior ADU & Interior Conversion Costs in Hobe Sound, FL
Junior ADU & Interior Conversion in Hobe Sound ranges from $45,000 to $130,000. Most projects we quote fall between $65,000 and $95,000.
Five factors push you toward the high or low end:
- Size and existing layout: Converting a 400-square-foot attached garage with existing slab and roof is simpler than reconfiguring 600 square feet of interior bedrooms and hallways. More demo, more framing, more finishes - the multiplier is real.
- Plumbing relocation distance: If your nearest drain stack is on the opposite side of the house, we’re running new lines through slab or attic. That adds $4,000-$8,000 versus tying in nearby.
- Electrical service capacity: Older Hobe Sound homes often have 150-amp panels. A Junior ADU & Interior Conversion with full kitchen and laundry typically needs 200 amps. Service upgrade: $3,500-$6,500, including Martin County electrical inspection.
- Material grade: Stock cabinetry and solid-surface counters keep you lean. Moving to KraftMaid or Wellborn semi-custom cabinets with Cambria quartz adds $8,000-$15,000 but holds value in Hobe Sound’s resale market.
- Permit complexity: Straightforward mainland conversions with no environmental buffers clear faster. Properties near the Hobe Sound National Wildlife Refuge boundary or Loxahatchee River flood zones trigger additional Martin County Development Review Committee scrutiny - not higher fees necessarily, but more documentation and longer timelines.
Our written estimates include demolition, framing, rough and finish mechanicals, insulation, drywall, flooring, cabinets, counters, fixtures, paint, trim, and the final inspection coordination. They do not include permit fees (typically $800-$2,200 in Martin County), designer or architect fees if you hire separately, or any work outside the conversion footprint like driveway modifications or landscaping.
What Hobe Sound Homes Specifically Do to This Job
Hobe Sound sits entirely within Martin County, which has among the most restrictive growth management and coastal construction regulations in Florida - deliberately so, as the county has legally defended its slow-growth policies against development pressure from Palm Beach County to the south. Contractors working here must navigate Martin County’s Coastal Construction Control Line setbacks, environmental buffers tied to the Hobe Sound National Wildlife Refuge, and Loxahatchee River-adjacent flood zone requirements that simply do not apply just across the county line in Jupiter or Palm Beach Gardens.
For Junior ADU & Interior Conversion specifically, this means three things. First, if your property is east of U.S. 1 or near the water, that separate exterior door we cut in may trigger a flood-vent requirement or elevated threshold detail that inland conversions skip. Second, the mainland side of 33455 is full of mid-century ranch homes from the 1960s through 1980s - homes that commonly lack modern hurricane strapping and require full tie-down upgrades when we pull a permit for structural modification. We’ve had inspectors flag original rafter ties on homes off Gomez Avenue and Bridge Road that looked fine but didn’t meet current wind-load standards. Third, Martin County’s Development Review Committee enforces environmental buffer rules tied to gopher tortoise habitat and wildlife refuge adjacency. Contractors from Broward or Palm Beach often get blindsided by stop-work orders on what appear to be routine ground-disturbing jobs near the refuge boundary on the north end of town. We know to check the refuge buffer map before we spec any exterior work, even something as small as a new entry stoop or walkway.
The salt-air corrosion is real, too. Within a mile of the Atlantic or the Intracoastal, we spec stainless or hot-dip galvanized fasteners, copper flashing instead of aluminum, and impact-rated door hardware. Standard hardware fails fast here. We’ve replaced exterior door hinges on oceanfront properties in Hobe Sound that were pitted through in under three years.
Serving Hobe Sound, FL - Our Local Coverage Area
We’re based in the Hobe Sound area and know this community well, serving Hobe Sound, FL. Use the map below to see our service coverage - if you’re nearby, we can almost certainly help.
Frequently Asked - Junior ADU & Interior Conversion in Hobe Sound
Most projects run 8-14 weeks from permit issuance to final inspection. Martin County’s permit review typically takes 2-4 weeks for Junior ADU & Interior Conversion plans, longer if your property triggers environmental buffer review near the wildlife refuge. Call (844) 665-0162 and we’ll check your specific address against the refuge boundary map.
Yes. Martin County requires a building permit for any structural modification, new plumbing, electrical subpanel, or separate exterior door. The permit classifies the work as either an accessory dwelling unit or an accessory living space depending on your kitchenette scope and zoning. We handle the application, the engineered drawings, and the inspection scheduling.
Sometimes, but rarely in the layouts we see. Most Hobe Sound homes from the ranch era have the plumbing clustered around the original wet core, and the space we’re converting - a bedroom wing, garage, or bonus room - sits too far from those drains. We can often minimize plumbing relocation by choosing a wet-bar kitchenette over a full kitchen, which reduces your rough-in scope significantly.
Typically yes. You’re leveraging existing roof, foundation, and envelope rather than building new. In Hobe Sound, where our Home Additions & ADU in Hobe Sound for detached units runs $90,000-$220,000 and must navigate setback and height restrictions, a Junior ADU & Interior Conversion at $45,000-$130,000 avoids the site work and foundation costs entirely. The trade-off is you’re giving up interior square footage from your main home.
We warranty our workmanship for one year from final inspection. Manufacturer warranties apply to specific products - KraftMaid or Wellborn cabinets carry their own coverage, as do Cambria countertops and the mini-split HVAC units we install. We register all warranties in your name and leave you the documentation. Any issues during the first year, we come back and fix them. Call (844) 665-0162 to discuss what’s covered in detail.
Get Your Free Estimate for Junior ADU & Interior Conversion in Hobe Sound
We’ll walk your property, measure the space, check your zoning and any refuge buffer or flood zone considerations, and deliver a written estimate with real numbers - no placeholder ranges. Call (844) 665-0162 or fill out our contact form. Raymond Estevez or a senior project lead will handle your walkthrough personally.
Written by Raymond Estevez, Owner at Groundwork Construction Co., serving Hobe Sound since our South Florida expansion.