Free written scope consultation - allowances, timeline, and change-order rules on paper before a single trade is scheduled
Before
After
Before
After
Before
AfterFast, Reliable Home Additions & ADU Across Sanibel
Adding square footage to a Sanibel home means building to a standard most mainland contractors never touch: pile foundations, 30-foot height caps, and FEMA flood rules that decide everything from your finished-floor height to which fasteners your crew uses. A home addition in Sanibel typically runs $45,000-$130,000, and a new detached ADU starts around $90,000. Barrett & Sons Construction has been building and remodeling elevated coastal homes since 1998, and we handle the permits, the pile work, and the paperwork so you don’t get a surprise bill at the final walkthrough. Call (877) 610-1318 to schedule your free estimate.
We know what opening up a 1972 Sanibel cottage actually turns up. We know the causeway schedule, the inspector’s load-path requirements, and why a $45,000 addition quote that skips the pile retrofit is not a deal, it’s a problem waiting on a date.
Why Barrett & Sons Construction Is Sanibel’s Preferred Home Additions & ADU Company
Tom Barrett puts his name, address, and license number on every contract and every page of this site. Look it up before you sign anything. That’s how we’ve done business since 1998, and it’s how we handle every Home Additions & ADU job on Sanibel, from a single-room bump-out to a full detached ADU with its own utility service.
Most Sanibel homeowners we meet have already been burned once by a company that quoted over the phone and delivered a different number at the door. We don’t work that way. Every scope change, every allowance adjustment, every surprise from a 1970s wall cavity gets priced in writing before we touch it. The permit inspector works for you, not for me, and that’s exactly why we like him.
Crews serving Sanibel are Tom’s sons and their teams, not dispatched labor from an out-of-state office. Dispatch and scheduling are coordinated from our South Florida office, but the people swinging hammers on Sanibel wear the Barrett & Sons name and answer for it. A live person answers our phone 24/7. Call at midnight from Sanibel and you’ll get a voice, not a voicemail box.
Key takeaways before the details:
- Sanibel residential additions and ADUs must meet FEMA pile-foundation rules and a 30-foot height cap in many overlay zones, not the looser Lee County mainland standards.
- Written change orders before any scope change touches your job. No exceptions, no verbal handshakes.
- Our crew knows Sanibel’s sandy substrate, high water table, and salt-air corrosion patterns. That knowledge changes how we price and how we build.
- Estimates are free, and every completed job carries the 90-Day Done Right Promise in writing.
Our Home Additions & ADU Services in Sanibel
ADU Design & Permitting
An ADU on Sanibel is a code project first and a construction project second. We start every ADU with a review of your lot’s FEMA flood zone, the Sanibel Land Development Code height overlay for your specific street, and the required Base Flood Elevation for the finished floor. From there we design the structure, the foundation system, and the paperwork package. Permits get pulled, inspections get signed, and you know what the city requires before the first pile goes in the ground.
Garage Conversion ADU
Converting a ground-floor garage on Sanibel means confronting a hard truth: most garages here sit below the required flood elevation. That means either floodproofing the lower level as a non-habitable enclosure or raising the living space above BFE. In some zones, the city will require a full pile retrofit. We’ll tell you that in the first conversation, not after the demo is done. A garage conversion ADU in Sanibel typically runs $30,000-$80,000 depending on whether the conversion triggers a foundation elevation.
New Detached ADU
A new detached ADU on Sanibel gives you the most design freedom, but it also puts the city’s toughest requirements on full display: pile embedment depth in loose sandy soil, breakaway lower-level walls if you’re in a V-zone, impact-rated windows throughout, and a roof line that stays under the height overlay. We build new ADUs from treated-timber or concrete piles up through finish, and we coordinate the separate utility runs, the electric service upgrade if you need it, and the final inspection sign-off. Expect $90,000-$220,000 for a properly permitted, elevation-compliant detached ADU.
Junior ADU & Interior Conversion
A junior ADU tucked inside your existing footprint is usually the fastest and least expensive way to add rentable or family space on Sanibel. The catch is that interior conversions still trigger the same code review: as soon as walls open, the city asks about the wiring, the lateral bracing, and the flood elevation of the finished space. If your existing home already sits above BFE and the conversion stays within the old footprint, you’re ahead. If not, we’ll show you the upgrade path in writing before any demo starts.
What happens when you call
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A real person answersNo phone trees - you reach a local pro.
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You get an upfront price rangeHonest numbers before anyone is dispatched.
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A background-checked tech heads outLicensed & insured, dispatched right away.
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You approve before work beginsNothing starts until you say go.
Trusted Brands We Service in Sanibel
We don’t use mystery materials off a van. On Sanibel, the salt air and humidity eat cheap hardware in one wet season, so we spec what holds up. Our team installs and stands behind brands like Schluter waterproofing systems in wet areas, GAF roofing on any tied-in roofline between the addition and the existing structure, and Sterling fixtures where a tub-to-shower conversion is part of the scope. You can look these brands up, see the warranty, and hold us to the same standard. That’s the point.
Common Home Additions & ADU Problems We See in Sanibel Homes
- Height cap collisions. A homeowner wants a second-story bonus room over a new addition, the permit goes in, and the city flags it because the pile height plus floor assembly plus roof pitch clears 30 feet. Contractors using mainland Lee County takeoffs miss this every time. We check the height overlay before we draw the first line.
- Salt-air hardware failure. Standard galvanized fasteners on a ground-contact deck ledger rust through within one wet season on Sanibel. We spec hot-dipped galvanized or stainless connectors on every exterior connection and every pile-to-beam tie.
- Old 1972 aluminum wiring. Sanibel’s pre-Ian slab-on-grade cottages regularly hide aluminum branch circuits corroded by decades of salt air. Open the wall and the code trigger says you’re re-feeding the circuit. We write that into the change order before rough-in, so you approve the number in writing.
- Skipped pre-drywall inspections. The homeowner who skips the pre-drywall inspection to save a day gets a final sign-off rejection later, then has to open walls so the inspector can see the load path. That triples the punch list time and adds thousands. We schedule the inspection. It’s not optional for us.
Pricing for Home Additions & ADU in Sanibel, FL
Here’s the honest math for Sanibel. Pile foundations, elevation requirements, impact-rated windows, and the single-causeway material logistics all push costs higher than a comparable mainland job. That’s the market here, and it’s not negotiable if you want the permit to pass and the house to survive the next storm.
| Project | Sanibel Price Range |
|---|---|
| Home Addition | $45,000-$130,000 |
| ADU Construction | $90,000-$220,000 |
| Garage Conversion ADU | $30,000-$80,000 |
What moves these numbers: whether your lot sits in a V-zone or A-zone, how deep the piles need to go in your specific soil, whether the existing structure’s wiring and lateral bracing survive a code-triggered review, and whether the height overlay allows the roofline you want. Every scope item and every allowance goes on paper before work starts. Call (877) 610-1318 for a free estimate with real numbers, not a phone quote you can’t hold us to.
We also offer a free second opinion on any written estimate, no trip charge inside the county, $40 off any repair over $200, and a permanent 10% senior and veteran discount. Those are the standing offers. Nothing hidden, nothing invented.
We Also Serve Cities Near Sanibel
Our crews regularly work Sanibel to Fort Myers Beach, Iona, Cypress Lake, and McGregor. If you’re just over the causeway and wondering whether we’ll come out, the answer is yes. For a full overview of our work across the island, see our Home Additions & ADU in Sanibel guide.
Serving Sanibel, FL - Our Local Coverage Area
We’re based in the Sanibel area and know this community well. Use the map below to see our service coverage - if you’re nearby, we can almost certainly help.
FAQs - Home Additions & ADU in Sanibel
Yes, in most cases. Sanibel’s FEMA flood zones require new habitable space to sit at or above Base Flood Elevation, and because the island’s average elevation is only 3-4 feet above sea level, that almost always means elevating the ADU on piles even if the original 1970s cottage sits on a slab. The city will not let you add new habitable square footage below BFE in most overlay zones. Call (877) 610-1318 and we’ll check your specific lot’s flood zone and required elevation before you spend a dime on design.
It depends on your garage’s elevation relative to BFE and your zone’s height overlay. Most Sanibel garages sit below BFE, which means the city typically treats the conversion as either a floodproofed non-habitable enclosure or requires raising the living space. We’ll tell you which path applies to your property in the first conversation, in writing, with the permit requirements laid out. Estimates are free.
You get a written change order. When we open a wall and find aluminum branch circuits or salt-corroded connections, the city requires the circuit to be brought to current code before we close the sheathing. We price the re-feed, put it on paper, and you approve it before we touch the rough-in. That’s the difference between a contractor who surprises you at the end and one who hands you the number before the work happens.
We check the Sanibel Land Development Code height overlay for your specific parcel before we draw. Many residential zones cap structures at 30 feet from grade, and once you add pile height for FEMA elevation, the finished floor, and the roof pitch, you can clear that limit fast. Mainland contractors miss it. We don’t, because the permit gets rejected if we do. Call (877) 610-1318 for a free lot review.
Yes. The ADU’s electric service, water line, and sewer or septic connection each require their own permit and inspection, and the city coordinates them through the main building permit. We handle all of it, including the load calculation if your existing panel can’t carry a second dwelling unit. It’s all on the permit schedule before the first pile goes in.
Written by Tom Barrett, Owner at Barrett & Sons Construction, serving Sanibel since 1998.