What a New Detached ADU in Lely Actually Costs and How Long It Takes
A new detached ADU in Lely typically runs between $90,000 and $220,000, with most single-bedroom units falling in the $120,000 to $160,000 range once site work, utility runs, and finishes are factored in. The build takes five to eight months from permit approval to final inspection, not counting the two to four weeks you’ll spend in Architectural Review Committee review before Collier County even sees your plans. Call (844) 638-7249 for a written, line-item estimate on your specific lot - there’s no charge and no obligation.
How We Build a Detached ADU in Lely - The Real Sequence
Every standalone unit we build in Lely Resort follows the same structured sequence. We’ve refined this over hundreds of projects, and we walk you through every decision point so nothing blindsides you. Here’s what the five stages look like.
Stage 1: Site Survey, ARC Package, and Permitting (Weeks 1-6)
The first thing we do is pull a full survey of your lot - setbacks, easements, swale locations, and any existing underground utility paths. In Lely, this survey becomes the foundation of your ARC submission. The Lely Resort Architectural Review Committee requires elevation drawings, a materials list that matches the community palette, and a site plan showing the ADU’s relationship to your primary structure and any canal or lake buffers. We prepare the full package, walk it through ARC review, and handle any revision requests. Once ARC signs off, we submit to Collier County for the building permit. This dual-approval gauntlet is non-negotiable in Lely, and a contractor who has never worked inside the resort will typically burn four extra weeks on resubmissions. We don’t.
Stage 2: Site Prep, Dewatering, and Foundation (Weeks 6-10)
This is where Lely’s geology gets real. The water table across much of the community sits 18 to 24 inches below grade, especially on lots near the canal system. The moment we excavate for footers, we hit groundwater. We arrive with dewatering pumps and silt-fencing already spec’d in the site plan, so there’s no scramble and no county stop-work order. Footers are poured, block stem walls go up, and the slab gets poured with vapor barrier and termite pre-treatment. You’ll choose your foundation type during permitting, but most Lely ADUs go on a monolithic slab with thickened edges - it’s the right call for our soil conditions and it keeps the build moving.
Stage 3: Framing, Roof Tie-In, and Drying-In (Weeks 10-16)
Your ADU gets framed in either engineered wood trusses or conventional stick framing, depending on span and ceiling height. In Lely, we match the roofline and material to your primary home’s profile - barrel tile over underlayment rated to current Florida Building Code - because the ARC will check that roofline against the community standard during the rough-in inspection. We sheath, paper, and dry-in the structure, then cut window and door openings. This is when you’ll make your window and exterior door selections if you haven’t already. We use impact-rated products exclusively; Lely homes built in the ’90s and early 2000s often still carry original single-pane units that are nowhere near current wind-missile standards, and a detached ADU gets permitted under today’s code, not the code from when the main house went up.
Stage 4: Rough-Ins - Electrical, Plumbing, HVAC (Weeks 16-20)
We trench and run a new electrical service lateral from your existing panel or, if load calculations require it, a dedicated sub-panel on the ADU itself. The underground plumbing tie-in to your existing sewer lateral or septic system gets routed around any swale or canal buffer - Collier County inspects this trench before we backfill, and Lely’s stormwater management district takes buffer encroachment seriously. HVAC goes in as a mini-split system or a small ducted unit depending on square footage; mini-splits are the common choice here because they avoid the attic space constraints typical of 1990s-era Lely homes. Rough-in inspections happen at this stage, and we walk the job with the county inspector.
Stage 5: Insulation, Drywall, Finishes, and Final (Weeks 20-28)
Closed-cell spray foam or batt insulation goes in, drywall gets hung and finished, and we move into your interior selections: flooring, trim, fixtures, countertops, cabinet style and color. Humidity in Lely during the May-through-October window extends drywall mud cure times by a day or two per coat, so we build that into the schedule rather than rushing it and fighting adhesion problems later. Trim-out, paint, final electrical and plumbing fixtures, and a final county inspection close the job. Before we hand you the keys, we do our own punch-list walkthrough - and everything we built is covered by our 730-Day Done Right Promise. If it’s not done right, we make it right.
Many homeowners pair an ADU build with interior upgrades on the main house. We regularly handle Kitchen Design & Layout in Lely or Backsplash, Tile & Flooring in Lely while the ADU is underway, which keeps the disruption consolidated into one project window.
The Choices You’ll Make When Building a Detached ADU
You’re not just picking paint colors. These are the five decisions that most affect the final cost and how the unit lives day to day. We walk through every option during the design consult so you understand the trade-offs before a single dollar gets committed.
- Square footage and layout. A 400-square-foot efficiency with a kitchenette and full bath hits the lower end of the range. A 750- to 900-square-foot one-bedroom with a full kitchen, living area, and separate bedroom lands in the middle. Every additional square foot adds foundation, framing, roofing, and finish costs. If the unit will house a family member long-term, we recommend at least 600 square feet for genuine livability - smaller units pencil out cheaper but feel tight fast.
- Foundation type. Monolithic slab is the standard for Lely lots; it handles our water-table reality well and costs less than a stem-wall or pier foundation. If your lot sits immediately adjacent to a canal or swale and the county requires a more substantial engineered foundation, expect the concrete and rebar numbers to climb.
- Kitchen and bath finish level. This is where two ADUs of identical square footage can separate by $30,000. Stock cabinets, laminate counters, and a basic fiberglass shower pan keep costs lean. KraftMaid cabinetry, a Cambria quartz countertop, Kohler fixtures, and a tiled walk-in shower push you higher - and deliver a unit that looks and feels like a custom home, not a converted shed. We spec from the same brand partners across every trade, so you’re never forced into the builder-grade default unless you choose it.
- HVAC system. A ductless mini-split handles cooling and heating for most Lely ADUs efficiently and costs less to install than a full ducted system. If the unit exceeds 800 square feet or you want zoned temperature control in separate rooms, a small ducted system with an air handler in a closet or attic knee-wall becomes the better choice.
- Utility tie-in distance. The farther your ADU sits from the main house’s electrical panel and sewer lateral, the more trenching, conduit, and pipe you’re paying for. On larger Lely Resort lots, a 100-foot trench run versus a 30-foot run can add several thousand dollars before the first wire gets pulled.
What a New Detached ADU Costs in Lely, FL
A new detached ADU in Lely costs $90,000 to $220,000. That range covers everything from a compact efficiency unit with basic finishes to a fully appointed one-bedroom with premium kitchen and bath selections. Most of our Lely builds close between $120,000 and $160,000.
What pushes a project to the high end? Five variables move the number more than anything else. Square footage is the multiplier that touches every trade. Site conditions - particularly how close the water table sits to your footer depth and how far the unit sits from existing utility connections - add excavation and trenching cost. Finish grade is the lever you control most directly; stock-versus-custom cabinets and laminate-versus-quartz counters swing the interior trim budget. Foundation and structural requirements change if your lot is within a canal buffer zone and the county requires a more substantial foundation design. Permit and impact fees are fixed costs in Collier County, but the ARC review process adds no county fee - it adds time, and we build that into the schedule from day one.
Every estimate you get from us is a written, line-item document. It shows exactly what’s included - site prep, foundation, framing, roofing, windows, doors, electrical, plumbing, HVAC, drywall, finishes, permit fees - and anything outside the contracted scope gets its own change-order conversation before work proceeds. There’s no buried markup and no “we’ll figure it out later” open ends. As part of our larger Home Additions & ADU in Lely work, every detached unit gets the same upfront pricing standard.
What Lely Homes Specifically Do to This Job
Building a detached ADU in Lely is a different animal from building one almost anywhere else in Collier County, and it’s not subtle. The Lely Resort Architectural Review Committee controls what gets built here with a level of rigor that surprises homeowners who have never gone through it. Before Collier County will process a building permit, you need ARC approval - and that means your ADU’s roofline profile, exterior material palette, window style, and even paint color must match the community’s published standards. We submit ARC packages routinely and know what passes on the first round. Contractors who treat Lely like any other unincorporated county job site get rejected, revise, and resubmit while the homeowner’s timeline slides by weeks.
The housing stock itself shapes what we do. Most Lely homes were built between the mid-’90s and mid-2000s - concrete block stucco with original barrel tile roofs. When we run a new electrical lateral for an ADU, we’re tying into a panel that was sized for a house built before today’s code-mandated loads were even contemplated. Load calculations often push us toward a dedicated sub-panel, and that’s factored into the estimate from the start. The water table compounds the site-prep challenge; we hit groundwater on nearly every excavation in Lely, and dewatering is not optional, it’s baked into the schedule and the price. The community’s canal and swale network imposes strict no-disturbance setbacks, so ADU placement on the lot sometimes gets dictated as much by stormwater buffers as by the zoning envelope.
And because so many Lely homeowners are seasonal, we schedule the bulk of construction during the May-to-October window when they’re away. That window overlaps with peak rainy season. Afternoon thunderstorms shut down exterior work regularly, humidity stretches drywall and stucco cure times, and we plan the schedule around those realities rather than pretending they don’t exist. Our home additions & adu crew has been building through Southwest Florida summers long enough to know what you can rush and what you absolutely cannot.
For any other work around your property, we cover the full scope of Lely service needs, from roofing to windows to hardscape.
Serving Lely, FL - Our Local Coverage Area
We’re based in the Lely 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 - New Detached ADU in Lely
Five to eight months from permit issuance to final inspection, with an additional two to four weeks upfront for ARC review. The variables that stretch the timeline are custom finish lead times, weather shutdowns during the May-October rainy season, and any ARC revision requests. We provide a week-by-week schedule at contract signing and update it as the job moves. Call (844) 638-7249 to discuss your timeline - we’ll give you a realistic window, not a sales pitch.
Yes. Every detached structure in Lely Resort, including an ADU, requires Architectural Review Committee approval before Collier County will accept your building permit application. The ARC reviews roofline, exterior materials, colors, and site placement against community standards. We prepare the full submission package and handle any revision rounds. This is not optional, and it’s not bypassable - it’s the first gate every Lely project passes through.
Yes. Most detached ADUs we build in Lely include a full kitchen with range, refrigerator, sink, and cabinetry, plus a full bathroom with a shower or tub. The unit gets its own electrical service and plumbing tie-in to the existing sewer lateral or septic system. A kitchenette - microwave, small fridge, sink, no range - drops the cost modestly but limits the unit’s functionality as a long-term living space.
Every ADU we build is covered by our 730-Day Done Right Promise. If something isn’t done right within two full years of completion, we make it right at no cost to you. That’s one of the longest workmanship guarantees you’ll find in residential construction, and it’s not pro-rated or conditional on a dozen carve-outs. Materials carry their own manufacturer warranties, and we walk you through what’s covered under each before you sign.
The estimate is a written, line-item document covering site prep, foundation, framing, roofing, windows, doors, electrical, plumbing, HVAC, drywall, insulation, finishes, and permit fees. It shows exactly what’s in scope. If you change the scope - upgrade countertops, add square footage, move a wall - we price the change order before any new work begins. If the scope doesn’t change, the price doesn’t change. Groundwork Construction Co. runs on upfront pricing with no buried costs, and we’ve done it that way since 2014.
Get a Free, Written Estimate for Your Lely ADU
We’ll walk your lot, talk through what’s possible given your setback envelope and ARC requirements, and deliver a line-item price with no obligation and no pressure. Every call is answered by a live person - not a voicemail box that might get checked on Monday. Reach us at (844) 638-7249 to schedule your free on-site estimate for a new detached ADU in Lely. From foundation to finish line, we build it backed in writing.
Written by Derek Hollenbeck, Owner at Groundwork Construction Co., serving Lely and surrounding communities with full-scope home construction since 2014.