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James Hardie Home Additions & ADU: The Jacksonville Owner’s Guide
A James Hardie home addition or ADU in Jacksonville typically runs $45,000 to $130,000, depending on square footage, foundation work, and whether you’re adding a full kitchen and bath or a simple bedroom bump-out. We stock the James Hardie siding, trim, and soffit products needed for these builds and can usually start framing within two to four weeks of permit approval. Most Jacksonville homeowners discover they need help when they realize their existing Hardie siding has been absorbing moisture around a failed window flashing or a rotted eaves line, which means the new addition has to tie into compromised structure before we even start.
What you’re really buying with a home addition is a weathertight envelope. In Jacksonville’s heat, humidity, and afternoon thunderstorms, James Hardie fiber cement is one of the few siding products that holds its paint and resists rot. But if the existing Hardie around the tie-in point has failed, the new work inherits that failure. So the first question we ask on any addition or ADU quote is not what you want to build. It’s what the existing exterior is doing where the new roofline meets it.
- Jacksonville home addition pricing: $45,000 – $130,000, with ADUs running higher when they include a kitchen or separate utility service.
- Bradford Remodeling Co Jacksonville is an independent remodeler, not affiliated with James Hardie. We install and repair James Hardie products, but the product warranty stays with the manufacturer.
- Every project gets a written price before work starts, and every completed job carries our 365-Day Done Right Promise.
- A live person answers our phone 24/7 at (904) 337-5929.
Which James Hardie Models This Applies To
If you’re adding onto a Jacksonville home built since about 1990, there’s a good chance the exterior is James Hardie HardiePlank lap siding, HardiePanel vertical siding, or HardieTrim boards. The product matters because your addition’s exterior has to match the existing elevation, and Hardie products are not interchangeable with vinyl or wood without looking like an afterthought. The most common Hardie lines we tie into are HardiePlank lap siding in 5/4-in exposure and 8-1/4-in exposure, HardiePanel for gable ends and shed-style roofs, and HardieSoffit for eaves and porch ceilings. If your home has HardieShingle or the newer Hardie Architectural Collection, the match gets trickier because those profiles have been discontinued or reformatted in some regions. We identify the exact product by pulling a piece off a hidden area and checking the edge marking, which carries the Hardie product code, thickness, and lot number.
The OEM-versus-aftermarket question matters here. For trim and soffit, we use genuine James Hardie products because the color, texture, and joint behavior match the existing elevation. For structural lumber, sheathing, flashing, and fasteners, we use code-spec equivalents from name-brand suppliers, not no-name imports. The one compatibility gotcha Jacksonville homeowners hit constantly is fasteners. Hardie requires hot-dipped galvanized or stainless nails, not electroplated trim nails. Drywall screws and common bright nails corrode in our humidity and leave rust streaks down the siding inside two years. We’ve fixed that mistake on enough Riverside and San Marco additions to know it’s the first place shortcuts show up.
Styles & brands we work with
Signs Your James Hardie Home Additions & ADU Is Failing
- Rust streaks running down from nail heads. That means the original installer used bright or electroplated nails. The fastener is failing, not the Hardie. In Jacksonville’s salt air and humidity, it’ll only get worse, and the streaks etch into the paint. The fix is removing and replacing fasteners, then repainting, which is a job for a painter or siding crew.
- Swollen, soft, or dark edges at the bottom course of siding. Hardie should never touch grade. It needs a 6-in minimum clearance, and in Jacksonville’s heavy rain, we prefer 8 in. If dirt or mulch has built up against the bottom edge, the siding wicks moisture continuously and starts to delaminate at the cut edge.
- Gaps opening at butt joints between siding boards. Hardie moves with temperature and humidity. Original HardiePlank joints are often butted tight, which means expansion shows up as buckling or open seams. Proper joint gaps with flashing behind them are part of the manufacturer spec, and when we add onto a home with tight joints, we correct the worst of them at the tie-in.
- Caulk cracking around windows and door trim on the existing structure. This is a flashing failure, not a caulk problem. The caulk cracks because water is already moving behind it. On a Jacksonville afternoon, a 20-minute downpour can drive water behind poorly flashed trim, and that water ends up in the wall cavity where the new addition butts against it.
- Paint peeling in sheets rather than wearing thin. Hardie requires a primed face and edges before painting, and the cut edges need end-sealing. If the original painter skipped edge sealing, moisture enters the board at the cuts and pushes paint off in sheets. A new addition attached to that wall inherits the same moisture path.
See the difference
Before
After
Before
After
Before
AfterReplacement Cost & What’s Included
| Scope | Typical Jacksonville Price |
|---|---|
| Home addition (bedroom, office, or family room bump-out) | $45,000 – $130,000 |
| ADU with kitchenette and bath | $90,000 – $220,000 |
| Garage conversion to living space | $30,000 – $80,000 |
That price includes the full scope in writing before we start: plans and permit drawings where required, demolition of the tie-in area, framing, sheathing, weather barrier, James Hardie siding and trim matched to your existing elevation, roofing tie-in, electrical rough-in and finish, insulation, drywall, paint, and a signed 365-Day Done Right Promise at closeout. What moves the number is the foundation. If your addition needs a monolithic slab with footing inspections, you’re adding $8,000 to $15,000 before a single stud goes up. If you’re on pier-and-beam or building a second-story addition over an existing first floor, the structural work changes the math again. We give you the line items, not a lump figure, so you can see exactly where the money goes.
DIY or Call Us?
You can check a few things without touching the siding. Look for rust streaks at nails, check whether the bottom course clears grade by at least 6 inches, and run your hand along the butt joints for gaps or buckling. That tells you what you’re dealing with before anyone shows up. What you should not do is attempt to pull and reset Hardie siding yourself, especially near window or door flashings. The boards are heavy, the cut edges are sharp, and the moment you expose the weather barrier behind them, the clock is running against Florida humidity. A mis-flashed window on a new addition in Jacksonville leaks inside a season, and by the time you see the stain on the drywall, the framing has been wet for months. Curtis Lane has walked more than a few Jacksonville additions where the homeowner tried to save on the tie-in and paid double to rip it out and redo it. Scope it right the first time – the job goes a lot smoother when nobody’s surprised. Call (904) 337-5929 and we’ll give you a written price before any work starts.
FAQs
James Hardie fiber cement carries a 30-year product warranty and in Jacksonville it commonly holds its finish for 12 to 18 years before repainting, depending on sun exposure and how well the installer sealed the cut edges. The siding itself will outlast that if it’s kept off grade and flashed correctly. Call (904) 337-5929 for an inspection and a written quote.
In most cases we can replace individual boards, re-flash the problem areas, and repaint the affected elevation rather than tearing out the entire wall. The exception is when the weather barrier or sheathing behind the Hardie has already been compromised by long-term moisture, which requires opening the wall. The estimate will tell you which one you have before we start.
Plan on four to eight months for a full addition from permit approval to final inspection, and six to ten months for an ADU with a kitchen and bath. Permit review times in Jacksonville and Duval County move at their own pace, and we build that into the schedule up front so you’re not surprised. Call (904) 337-5929 for a project-specific timeline.
We keep common James Hardie profiles and colors in stock for repair work, especially HardiePlank lap siding in popular Jacksonville widths and white, arctic white, and khaki trim boards. Large addition and ADU orders are placed per project with the manufacturer so the lot numbers match across the elevation, and we confirm availability before we finalize the schedule. We also stock and install KraftMaid cabinetry, Cambria and Silestone countertops, and other name-brand materials when the addition calls for them.
If your Jacksonville home needs a James Hardie addition or ADU, or your existing Hardie siding is failing at the tie-in point, call Bradford Remodeling Co Jacksonville at (904) 337-5929. We’ll walk the property, document the scope, and hand you a written price before any tools come out. A live person answers, day or night.
Written by Curtis Lane, Owner, Bradford Remodeling Co Jacksonville at Bradford Remodeling Co Jacksonville, serving Jacksonville and nearby areas.
