What a New Detached ADU in Gateway Actually Costs and How Long It Takes
A new detached ADU in Gateway, FL typically runs $90,000 to $220,000 and takes 5 to 8 months from the first site visit to final inspection. That range covers a fully permitted, freestanding unit with its own foundation, plumbing, electrical, and HVAC, built to meet both Lee County code and Gateway’s architectural review standards. If you’re researching whether the numbers work before you call, start with a free on-site estimate at (844) 638-7249, and we’ll give you a written, line-item quote that won’t change once we break ground.
How We Build a Detached ADU in Gateway, Step by Step
Most homeowners haven’t done this before, so we walk you through the real sequence. No skipping steps. No vague promises. Here’s what five months to eight months looks like when we handle your new detached ADU as part of our Home Additions & ADU services.
Stage 1: Site survey and architectural review prep (Weeks 1-3). Before any dirt moves, we survey the lot, flag utility lines, and pull the plat map. In Gateway, the CDD architectural review committee must sign off on the design, exterior finishes, roof profile, and even the color palette before Lee County will accept the permit application. We handle the full submittal, so you’re not chasing forms or attending committee meetings. What you decide here: ADU footprint, roofline style, door and window placement, and exterior materials that match the main house.
Stage 2: Foundation, underground rough-in, and slab pour (Weeks 3-6). Once the ARC approval and permits are in hand, we excavate, form, and pour the foundation. We run underground plumbing and electrical conduit at this stage, and the slab gets inspected by the county before the pour. Gateway’s sandy soil drains well, but it also shifts seasonally, so we compact the base and use steel reinforcement sized for local soil conditions. What you decide here: nothing structural. The slab is locked in by the approved plans.
Stage 3: Framing, roof, windows, and exterior (Weeks 6-12). The ADU takes shape fast once framing starts. We sheath the walls, set roof trusses, install impact-rated windows, and hang exterior doors. Roofing goes on right after the dry-in inspection. Given Gateway’s post-Ian insurance environment, we use a secondary water barrier under the roof covering as standard, not an upsell. Exterior stucco or siding comes next, matched to the existing home or adjusted per ARC approval. What you decide here: interior wall layout adjustments are still possible, but exterior changes get expensive after this point.
Stage 4: Rough-in and insulation (Weeks 12-16). Plumbing supply lines, electrical wiring, HVAC ductwork, and low-voltage cabling all go in during this window. We schedule the county’s rough-in inspection before insulation goes up. In a detached ADU, this is also when we trench and connect the separate electric panel and water line from the main house or the street tap, depending on utility placement. What you decide here: fixture locations, outlet placements, switch types, and any smart-home wiring you want pre-run.
Stage 5: Drywall, trim, finishes, and final inspections (Weeks 16-22+). Drywall, paint, flooring, cabinets, countertops, plumbing trim-out, light fixtures, and appliance hookups happen in sequence. The county performs a final building inspection, plus separate electrical, plumbing, and mechanical finals. We coordinate every inspection and walk you through the punch list. Once the CO is in hand, your ADU is a legal, rentable, insurable dwelling. What you decide here: paint colors, flooring material, cabinet style, countertop surface, and fixture finishes.
The Options You’ll Choose Between on a Gateway ADU Build
Every decision affects the final number and how the unit lives day to day. These are the real trade-offs we talk through with homeowners planning a new detached ADU in Gateway.
- Foundation type: slab-on-grade vs. raised pier. Slab is standard here, runs cooler, and costs less. A raised pier foundation adds $12,000-$22,000 but works better on irregular lots and gives you accessible under-floor plumbing. Most Gateway lots are flat enough that slab is the right call.
- Exterior finish: stucco vs. fiber-cement siding. Stucco matches most Gateway homes built between 1990 and 2010 and passes ARC review without pushback. James Hardie plank siding gives a different look and holds paint longer, but it runs $6-$10 more per square foot installed and may require extra justification during architectural review.
- Roofing: architectural shingle vs. standing-seam metal. Shingle roofs with a secondary water barrier are the budget-conscious choice and still meet wind-mitigation requirements when properly nailed. Standing-seam metal costs roughly double upfront but carries a 40-50 year life, lowers insurance premiums, and sails through the CDD’s roof-profile review because it looks clean and modern.
- Kitchen and bath finishes: stock vs. semi-custom. Stock cabinets and quartz-composite counters keep the ADU build in the $90K-$130K range. KraftMaid semi-custom cabinets with a Cambria quartz top push the interior finish cost higher but give you exact sizing and more door-style options. For a rental unit, stock finishes usually make more financial sense.
- HVAC: mini-split vs. ducted central. Ductless mini-splits cost less to install, zone efficiently, and avoid running ductwork through the attic of a smaller footprint. A full ducted system adds $4,000-$7,000 but delivers more even cooling in a unit over 600 square feet. In Gateway’s humid summers, proper sizing matters more than the system type.
What a New Detached ADU Costs in Gateway, FL
A new detached ADU in Gateway lands between $90,000 and $220,000, with most builds settling around $140,000-$170,000 for a 600-800 square foot one-bedroom unit with a full kitchen and bath. Here’s what moves the number.
Square footage is the biggest lever. A compact 400-square-foot studio sits at the low end. An 800-square-foot one-bedroom with a separate living area, full kitchen, and walk-in closet pushes toward $150K and up. Every additional 100 square feet adds roughly $18,000-$25,000 in finished cost.
Foundation and site work varies by lot. If the ADU sits close to the main house and we can tap existing utilities with a short trench run, site costs stay low. A far-corner placement that requires a separate electric-panel feeder, a longer water-line trench, and significant grading pushes site-prep costs up by $8,000-$15,000.
Interior finish level splits the range in half. Builder-grade flooring, stock cabinets, laminate counters, and basic lighting fixtures keep the unit functional and rentable at the lower end. Semi-custom cabinets, quartz or solid-surface counters, LVP flooring, and upgraded bath tile add $20,000-$35,000 to the total.
Permitting and impact fees are a real line item in Lee County. Gateway’s CDD adds an architectural review step that costs time but not a separate municipal fee beyond what the county charges. School impact fees, park fees, and utilities connection charges combined typically run $8,000-$14,000 for a new detached unit, and we line-item every one of those in your written estimate.
Our estimates are upfront pricing, no surprises. The number you see is the number you pay. We also offer 0% financing for 18 months and $1,000 off projects over $10,000. Call (844) 638-7249 to schedule a free on-site estimate for our Small Bathroom Remodels service in Gateway or your ADU.
What Gateway Homes Specifically Do to This Job
Gateway is not unincorporated Lee County. It’s a master-planned Community Development District built primarily between 1990 and 2010, and that CDD layer means every new detached ADU has to clear architectural review before the county ever sees the permit application. The committee cares about rooflines, exterior colors, door styles, and window profiles matching the existing community aesthetic. If your design looks like it belongs in a different neighborhood, it gets kicked back. We’ve worked with this committee enough to know what slides through and what draws redlines, so the submittal package we prepare addresses their concerns before they raise them.
The housing stock here also creates a specific set of constraints. Most homes are concrete-block construction with stucco exteriors and barrel-tile or flat-tile roofs. When we design a detached ADU in Gateway, we match the main home’s roof profile and stucco texture so the unit reads as part of the same property, not an afterthought. The post-Hurricane Ian reality also shapes how we build. While Gateway’s elevation kept it above the worst storm surge, the sustained winds took out plenty of soffits, screen enclosures, and underlayment. Insurance carriers across the community are now requiring documented wind-mitigation features as a condition of renewal, so we build every ADU with secondary water barriers, impact-rated windows, and upgraded strapping from the start. It’s cheaper to build it right than to retrofit it later when your insurer asks.
Serving Gateway, FL - Our Local Coverage Area
We’re based in the Gateway 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 Questions About New Detached ADUs in Gateway
Five to eight months is realistic, start to finish. The Gateway CDD architectural review adds 2-4 weeks upfront that unincorporated areas don’t face. Permitting through Lee County typically takes 4-8 weeks after that. Actual construction runs 14-20 weeks, depending on size and finish level, plus 1-2 weeks for final inspections and the certificate of occupancy.
Yes. Gateway’s CDD architectural review committee must approve the design before you can pull county permits. Exterior finishes, roof profile, color palette, and even the door style get reviewed. We prepare and submit the full package for you, with drawings and material specs that align with community standards, so you’re not stuck in a back-and-forth revision cycle.
In most cases, yes, but verify your specific zoning and any deed restrictions. Lee County generally allows accessory dwelling units as rental properties. We recommend checking with the Gateway CDD and your specific HOA subsection, because some neighborhoods within the district have rental-term minimums or other restrictions that aren’t universal across the community.
Most Gateway lots comfortably fit a 400-800 square foot unit without crowding the yard or violating setback requirements. The CDD and Lee County both enforce minimum setbacks from property lines, and we survey those constraints during the site visit. A one-bedroom, one-bath layout around 600 square feet hits the sweet spot for rental income versus construction cost.
No. We work on upfront pricing with a written, line-item estimate. If you don’t change the scope, the number doesn’t change. If something hidden surfaces during excavation, like unexpected debris or a utility conflict, we show you exactly what it costs to fix before we touch it. Most of our Gateway ADU builds stay on the original number because we account for local soil and site conditions in the initial estimate. Call (844) 638-7249 for a free quote.
Start Your Gateway ADU With a Free On-Site Estimate
A new detached ADU is a significant investment, and the best way to get an accurate number for your specific lot is a site visit. We’ll walk the property, discuss your goals for the unit, check setbacks and utility access, and give you a written line-item estimate with no obligation, whether you’re building an ADU or exploring our Small & Partial Kitchen Remodels service in Gateway. Our team handles everything from CDD architectural review through final inspection, and every build is backed by our 730-Day Done Right Promise. Call (844) 638-7249 to schedule yours. When you call, a live person answers, day or night. No voicemail, no waiting until Monday.
Written by Derek Hollenbeck, Owner at Groundwork Construction Co., serving Gateway homeowners with full-scope home construction and ADU builds.