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 Miami
A full home addition or ADU in Miami typically runs $53,100-$153,400, and the biggest variable isn’t square footage. It’s what’s inside your walls. The CBS concrete block construction, the Miami-Dade NOA product requirements, and the HVHZ wind-load rules that govern every permit change what a “simple” addition costs and how long it takes. If you’re planning a room addition, second story, or detached ADU in Miami, call Barrett & Sons Construction at (877) 610-1318 for a free estimate before you commit to anything. We’ll walk your property, check the existing structure, and give you a written scope with allowances in place for what we can’t see yet.
Why Barrett & Sons Construction Is Miami’s Preferred Home Additions & ADU Company
Tom Barrett started this company in 1998, and the way we do business hasn’t changed since: his name is on the truck, his sons run the crews, and every price change arrives in writing before one nail moves. Nobody in Miami gets a surprise invoice at the end of an addition. The allowance that isn’t on paper is a surprise waiting for a date, and we don’t work that way.
Miami homeowners keep calling us back because we understand what this county’s building code actually demands. The HVHZ standard isn’t a suggestion here. A contractor who passed inspections in Broward or Palm Beach can’t just waltz into Miami-Dade and pull a permit without knowing the NOA product rules. We know them. We’ve been pulling permits in Miami for years, and we’ve sat across the table from plenty of inspectors who sign off on our work because the load paths, fastener schedules, and waterproofing details are done right the first time.
Our Home Additions & ADU team works directly with Miami homeowners from the first walkthrough through final inspection. Tom answers his own phone. The crew that shows up at your house in Miami is the same crew you’ll see at the hardware store on Saturday. That’s the Barrett & Sons difference, and it’s why our repeat and referral business runs deep across the county.
Our Home Additions & ADU Services in Miami
ADU Design & Permitting
Every ADU in Miami starts with paperwork before concrete. We handle the full design, engineering, and permit package, including the Miami-Dade NOA product documentation the county requires. If your lot sits in a flood-prone western ZIP like 33142, we’ll check the elevation and aquifer depth before we ever draft a foundation plan. Miami limestone makes basement ADUs impossible, so we design what actually works here: slab-on-grade or elevated pier systems with proper drainage.
Garage Conversion ADU
Converting a Miami garage into an ADU runs $35,400-$94,400 depending on condition. Older garages in neighborhoods like Flagami and Little Havana often have flat built-up roofs past their service life and electrical panels that won’t pass a load calc. We strip back to sound deck, re-feed what the code demands, and install Windows & Doors - Miami with HVHZ ratings. The permit inspector works for you, not for me. That’s why I like him. When he signs off, it means the work is correct.
New Detached ADU
A new detached ADU in Miami is a ground-up build, typically $106,200-$259,600. That range reflects whether you need pilings, how far the utilities have to run, and whether the site sits within a mile of salt air. We use hot-dipped galvanized or stainless fasteners on every exterior connection because standard galvanized corrodes in under five years near the coast, and the inspector red-tags it at rough-in. We’d rather do it right once.
Junior ADU & Interior Conversion
Junior ADUs carve rentable space from existing square footage, often a large bedroom, den, or attached garage bay. In Miami’s CBS homes, this means cutting a new exterior egress door through eight inches of concrete block. That’s an engineered job with a proper lintel and HVHZ load-path calc. We handle the structural details, the waterproofing at the tie-beam, and the permit sign-off so your conversion is legal, insurable, and built to Miami-Dade standards.
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 Miami
The materials on your Miami addition matter as much as the framing. We install Techo-Bloc pavers for driveways, walkways, and ADU patios, Cambridge Pavers where the design calls for a wider color range, and Quikrete products for slab work and anchoring. These are brands you can look up, not mystery products off the back of a van, including Cover in Miami where specified. We keep common stock staged locally for Miami jobs, which means fewer delays when a change order adds a walkway or paver pad mid-project.
Common Home Additions & ADU Problems We See in Miami Homes
- Original aluminum wiring in 1950s-1970s CBS homes. When we open walls in neighborhoods like Flagami (33125) or along the 33124 corridor, we regularly find single-strand aluminum feeds that were never re-terminated. Code requires a re-feed once that wall is open. That’s a cost you didn’t plan for, which is exactly why we write wiring allowances into every Miami addition contract.
- Failed waterproofing at the tie-beam. Miami’s tropical monsoon climate pushes over 60 inches of rain a year, concentrated between May and October. On older CBS construction, the tie-beam flashing fails quietly, and the first sign is mold on the inside face of the wall. We strip it back, re-flash to HVHZ detail, and price the hidden rot before we touch it.
- Undersized or corroded anchors on exterior additions. Within a mile of the coast, salt air eats standard galvanized hardware in under five years. Miami-Dade code expects stainless or hot-dipped galvanized at every exterior structural connection. We spec that from day one, not after the inspector flags it.
- Flat built-up roofs past their service life. Much of Miami’s older stock has low-slope built-up roofs that were overdue for replacement a decade ago. Tying a new addition roof into that old system without stripping back to sound deck just bleeds the old problem into the new assembly. We open it, assess the deck, and write the repair scope before we marry the roofs.
Pricing for Home Additions & ADU in Miami, FL
Here’s what Miami homeowners can expect for the most common addition and ADU projects:
| Project | Miami Price Range |
|---|---|
| Home Addition | $53,100-$153,400 |
| ADU Construction | $106,200-$259,600 |
| Garage Conversion | $35,400-$94,400 |
| Impact Window Installation | $9,440-$29,500 |
These numbers reflect Miami-Dade’s HVHZ requirements, CBS construction methods, and the cost of NOA-approved materials. A second-story addition in a 1960s Flagami home will land differently than a ground-up detached ADU in a western ZIP with a high water table. We give every Miami customer a written line-item estimate, and if the scope moves once walls are open, you get a written change order with a price before we proceed. Call (877) 610-1318 to schedule your free estimate in Miami. The estimate is free, the scope is in writing, and the price doesn’t move without your signature.
We Also Serve Cities Near Miami
Beyond Miami proper, our teams cover Allapattah, Brownsville, Gladeview, and West Little River. If you live in one of these neighboring communities and you’re planning a room addition, ADU, or second story, the same HVHZ rules and NOA product requirements apply. Our Home Additions & ADU service area covers the full metro, and we’ll give you the same written scope and free estimate no matter which Miami-area neighborhood you call from.
Serving Miami, FL - Our Local Coverage Area
We’re based in the Miami area and know this community well, from Bathroom Remodeling in Miami to full home additions. Use the map below to see our service coverage - if you’re nearby, we can almost certainly help.
FAQs - Home Additions & ADU in Miami
Yes, you need a Miami-Dade NOA-approved window or door for any addition in Miami. Miami-Dade County operates under its own HVHZ code, which is stricter than the Florida Building Code used in Tampa, Jacksonville, and Orlando. A standard FBC product will not pass inspection here. We spec NOA-approved products on every window, door, and exterior opening, and we include those product numbers in your permit package so there’s no question at inspection. Call (877) 610-1318 if you want us to verify what’s already on your house.
Yes, we cut openings in CBS walls regularly across Miami. But it’s structural work, not a cosmetic cut. An opening in a load-bearing concrete block wall needs an engineered lintel, proper tie-downs, and an HVHZ load-path calc so the wall still handles 175 mph wind uplift. We don’t guess at beam sizing. We bring the engineer, we pull the permit, and the inspector confirms the calc before we close it up. If you’re in a CBS home in Flagami, Little Havana, or anywhere else in Miami, we’ll walk you through exactly what the opening requires and what it costs before we cut.
The price moves because Miami’s older homes hide problems behind the walls. When we open a 1960s CBS garage in a neighborhood like Flagami, we find original aluminum wiring, failed tie-beam waterproofing, or rusted anchors. Code requires fixing those once the wall is open. This is why we write allowances into every Miami contract before we start. The allowance covers the unknown, and when we find something, you get a written change order with a price before we touch it. No surprises at the end. Call (877) 610-1318 to discuss your project.
No. Miami sits on porous Miami Limestone with a water table that’s often less than two feet below grade in western ZIP codes like 33142. Basements aren’t built in Miami because they’d flood almost immediately. Any ADU here goes on a slab-on-grade foundation with proper drainage, or on elevated piers if your lot sits in a flood zone. Some out-of-state builders don’t know this until excavation starts. We know it before we draft the plan. Our ADU Site Prep & Utilities work includes a full site assessment so your foundation matches Miami’s actual ground conditions.
It depends on the scope of the addition and what the existing structure already has. When you add a second story in Miami, the permit review looks at the load path from the new roof down through the existing walls to the foundation. If the existing roof has Miami-Dade NOA products and proper straps, you may not need to touch much. If the original roof was never brought up to HVHZ standard, the county can require Miami Roofing upgrades as part of the permit. We’ll tell you what’s coming before you commit. That’s what the free estimate is for. Call (877) 610-1318 and we’ll walk your property, check what’s there, and put the full scope in writing.
Written by Tom Barrett, Owner at Barrett & Sons Construction, serving Miami and South Florida with permitted, written-scope home additions and ADUs since 1998. Tom publishes his name, address, and license number so you can look it up before you sign anything.
Ready to talk about your Miami addition or ADU? Call (877) 610-1318 today for a free estimate. A live person answers, we’ll schedule your walkthrough, and you’ll get a written scope with real numbers before any work begins. No voicemail maze, no out-of-state call center. Just Tom’s team in Miami.