Free written scope consultation - allowances, timeline, and change-order rules on paper before a single trade is scheduled
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AfterFast, Reliable Home Additions & ADU Across Sanibel
Home additions and ADUs in Sanibel run $45,000 to $130,000 for most projects, with garage conversions starting around $30,000 and full detached ADUs reaching $220,000 depending on pile elevation, impact-rated materials, and the island’s overlay-zone height limits. We schedule free estimates across Sanibel and walk your lot before a single number gets quoted, because a mainland quote that ignores FEMA Base Flood Elevations and the 30-foot overlay cap isn’t worth the paper it’s printed on. Call (877) 610-1318 and Tom Barrett or one of his sons will answer.
Sanibel is not a normal building site. Every addition, every ADU, every second story has to clear a permitting gauntlet shaped by Hurricane Ian, the Florida Building Code 8th Edition, and the Sanibel Plan’s height and setback rules. Our crews live with those rules on every job we take on the island. We’ve opened enough 1970s cottages and post-1992 stilt homes out here to know what’s behind the stucco before we quote it.
Why Barrett & Sons Construction Is Sanibel’s Preferred Home Additions & ADU Company
We’ve been in business since 1998, owner-operated from day one, and Tom Barrett’s name, address, and license number are published and verifiable. Look us up before you sign anything. That’s the point. We’re not a franchise dispatching strangers to your property; Tom and his sons are on-site most days, and the crew members who carry the Barrett & Sons name are background-checked and uniformed on every visit.
Sanibel homeowners have a particular reason to be suspicious of out-of-town contractors. The island’s rebuilding effort after Ian attracted every outfit with a truck and a logo. Some of them quoted mainland Lee County pile heights and 45-foot island-wide rules, then got red-tagged when the 30-foot residential overlay hit the permit desk. We don’t guess. We pull the lot’s actual zoning overlay, we check the FEMA flood map for the specific V-zone or A-zone designation, and we build the scope around what that lot legally allows.
Every price change on a Sanibel job comes as a written change order before work proceeds. Every scope item, every allowance, every permit fee is on paper. “An allowance that isn’t on paper is a surprise waiting for a date” is how Tom says it, and it’s why our Sanibel customers don’t get the five-figure surprise at the end. The permit inspector works for you, not for me. That’s why we like him here.
Our Home Additions & ADU Services in Sanibel
We handle the full range of Home Additions & ADU work on Sanibel, from small interior conversions to full second-story builds. These are the four services Sanibel homeowners call us about most.
ADU Design & Permitting
Most ADU projects on Sanibel stall at permitting, not at construction. Between the Sanibel Plan’s impervious-surface limits, FEMA pile-foundation mandates, and the island’s 30-foot residential overlay zones, a set of plans drawn for a mainland lot simply won’t clear. We handle the design review, the flood-zone documentation, and the permit package from the start, so you’re not paying for three rounds of county corrections.
Garage Conversion ADU
Garage conversions on Sanibel typically run $30,000 to $80,000, and the single biggest variable is what we find when walls come open. On East Gulf Drive, our crew opened a 1970s cottage for a garage conversion ADU and found original cloth-wrapped wiring, rotted sill plates, and no waterproofing behind the stucco. We wrote a change order for a full rewire, pressure-treated stem-wall repair, and fluid-applied flashing with rough-in inspection sign-off before closing anything up. The same week, two other contractors quoted the job without opening a single wall.
New Detached ADU
A new detached ADU in Sanibel runs $90,000 to $220,000, and the pile foundation is where budgets get made or broken. Sanibel’s high water table and loose sandy substrate require treated-timber or concrete piles embedded deep enough to satisfy FEMA and the building code. We spec hot-dipped galvanized connectors and ground-contact pressure-treated framing throughout, because salt air eats standard hardware in a few seasons out here.
Junior ADU & Interior Conversion
Interior conversions and junior ADUs are the most straightforward path when the existing envelope is sound. We convert underused interior space, enclosed patios, or attached storage into legal dwelling units, with impact-rated windows and doors throughout. Still, any Sanibel interior conversion triggers code upgrades once we open walls, which is why our contracts include unit-price allowances for hidden damage tied to your home’s age band.
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 install mystery materials off a van. On Sanibel ADUs and additions we regularly spec Schluter waterproofing systems in wet areas, Sterling fixtures where durability matters, and GAF roofing on any new roofline we add. These are brands you can look up. We order from local Sanibel and Fort Myers-area suppliers, and we stage materials to work around the causeway’s single-chokepoint logistics, so a missing board doesn’t idle your whole crew for a day.
Common Home Additions & ADU Problems We See in Sanibel Homes
Sanibel’s pre-Ian housing stock is specific, and it fails in specific ways. Here’s what we run into most often when opening island homes:
- Cloth-wrapped and out-of-code wiring from the 1960s and 70s, now corroded by salt air. Once we open a wall for an addition, the panel and branch circuits usually have to come up to current code. That’s not a surprise if it’s in an allowance; it’s a five-figure shock if it isn’t.
- Rotted sill plates and rim joists at the base of slab-on-grade cottages. Ian’s surge and the persistent humidity in Sanibel rot ground-contact framing fast. We inspect the stem wall and sill before we quote any tie-in work.
- Failed or missing waterproofing behind stucco and lap siding. Salt-driven rain gets behind the cladding and sits there. You won’t see it until the wall is open.
- Undersized or rusted structural connectors on elevated homes. Post-1992 stilt homes sometimes got light-gauge hardware that’s now corroded. Code requires hot-dipped galvanized or stainless replacement hardware for any alteration.
Pricing for Home Additions & ADU in Sanibel, FL
Sanibel pricing reflects island logistics, FEMA-required pile work, impact-rated materials, and the strictness of the local building department. A mainland quote that ignores any one of those will drift once a permit lands on a plan reviewer’s desk. Here are the ranges we see on actual Sanibel jobs:
| Service | Typical Sanibel Range |
|---|---|
| Home Addition | $45,000 - $130,000 |
| ADU Construction | $90,000 - $220,000 |
| Garage Conversion | $30,000 - $80,000 |
| Second Story Addition | $45,000 - $130,000 |
These are real numbers, not phone quotes. A garage conversion that lands at the low end assumes we find sound framing, modern wiring, and a compliant slab. A second-story addition at the high end assumes new helical piles or concrete pilings, full impact-rated window packages, and a roof pitch that respects the 30-foot overlay. We write every allowance and every scope item into the contract before work starts. Call (877) 610-1318 for a free estimate. It’s free because Tom wants to see the lot and the house before he gives you a number he has to stand behind.
We Also Serve Cities Near Sanibel
If you’re on the water or just off-island, we also serve Sanibel‘s neighbors: Fort Myers Beach, Iona, Cypress Lake, and McGregor. The permitting rules differ once you cross the causeway to the mainland, so we re-check every lot against Lee County standards before quoting. The same written-change-order process applies everywhere we work.
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
On Sanibel’s 1960s and 70s cottages, we most often add a full rewire, pressure-treated stem-wall or sill repair, and fluid-applied flashing behind the existing cladding. Those three items account for the majority of change orders on our island jobs, and that’s exactly why we build unit-price allowances for them into your contract before demo starts. You approve every change in writing before we touch it. Call (877) 610-1318 and we’ll walk you through how the allowance works on your specific house.
A permit means a county inspector signs off on the structural, electrical, and flood-plain work. On Sanibel, where a second-story addition has to comply with FEMA pile requirements and a 30-foot residential overlay cap, the inspector is the one who confirms your contractor didn’t cut a pile-embedment corner or exceed a height limit that would red-tag you later. The permit inspector works for you, not for the contractor. We like that.
Sanibel’s Land Development Code caps buildings at 45 feet island-wide, but many residential overlay zones cap structures at 30 feet measured from grade. When you add FEMA-required pile elevation on top of a finished floor and a roof pitch, a plan drawn to the 45-foot rule busts the 30-foot overlay and gets stopped at permitting. We check your lot’s specific overlay before we draw anything. Call (877) 610-1318 if you want us to look up your parcel before you spend a dollar on plans.
Everything exposed to Sanibel’s salt air and periodic saltwater inundation should be hot-dipped galvanized or stainless steel connectors, with pressure-treated lumber rated for ground contact in all subfloor framing and stem walls. Concrete or fiber-cement exterior finishes last longer out here too. We write these specs into every ADU quote, not as an upgrade line item. It’s what the building department out here expects to see at rough-in inspection.
We stop work, photograph it, price the repair, and hand you a written change order before we order a single board. You approve the number, or we talk through alternatives. What we don’t do is bury it in the final bill. That’s the difference between a written-allowance contract and a handshake. On Sanibel, where hidden rot is common in the older slab-on-grade cottages, that difference is usually worth five figures.
If you’re planning a home addition or ADU in Sanibel, start with a free estimate and a walk of your lot. We’ll tell you what’s possible under your parcel’s zoning before you spend money on plans. Call (877) 610-1318 now. Tom or one of his sons will answer.
Written by Tom Barrett, Owner at Barrett & Sons Construction, serving Sanibel since 1998.