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James Hardie Home Additions & ADU: The Fort Lauderdale Owner’s Guide
A James Hardie home addition or ADU in Fort Lauderdale typically runs $45,000 to $130,000 installed, depending on square footage, foundation work, and whether you’re building up or out. We stock James Hardie siding, trim, and HardieBacker board for additions and ADUs across Fort Lauderdale, and we can typically match your existing Hardie profile without a full re-side. Most owners call us because their existing Hardie siding has failed at the seams or their addition was quoted by someone who doesn’t know Fort Lauderdale’s wind and moisture codes. The good news: the right siding choice is usually a correction, not a rebuild.
We’re Sawyer Remodel Fort Lauderdale, an independent remodeling contractor. We’re not affiliated with James Hardie, but we install and source their products every week because they hold up better than anything else in South Florida’s humidity and hurricane cycles. When a Fort Lauderdale homeowner sees cracked HardiePlank, swollen trim, or gaps where the siding meets the roofline, that’s when they call us. The fix usually involves matching the existing profile, replacing the damaged boards, and making sure the new addition or ADU gets the same exterior treatment from day one.
Which James Hardie Models This Applies To
Most Fort Lauderdale additions and ADUs use HardiePlank lap siding (the horizontal boards), HardiePanel vertical siding, or HardieShingle for accent walls. The product line matters because the profile depth and reveal differ: HardiePlank comes in 4″, 5″, 6″, 7″, and 8″ exposures, and if you match the wrong reveal, the patch job looks like a patch job. We check the back of an existing board for the printed product code before ordering anything. If your existing siding is older, it’s likely HardiePlank HZ5, which was the standard for years. Newer installations in Fort Lauderdale should be HZ10, which has a slightly different edge profile and better moisture resistance for our climate.
On the OEM versus aftermarket question: for siding and trim, we always use genuine James Hardie products. The reason is warranty continuity and color matching. James Hardie’s ColorPlus finish is factory-applied and carries a 15-year finish warranty, but only if you use genuine boards. Aftermarket fiber cement boards exist, but the color match on a Fort Lauderdale addition is never exact, and the difference shows within six months of UV exposure. For backer board inside the ADU, HardieBacker is the standard, but we’ve also used equivalent cement board from USG when a client’s budget demands it. The difference is minimal for interior tile substrate. For exterior cladding, don’t cut corners.
Styles & brands we work with
Signs Your James Hardie Home Addition or ADU Is Failing
- Seam separation at the butt joints. Fort Lauderdale’s humidity cycle swells and shrinks fiber cement at the seams. If the caulk has failed and you see vertical gaps, water is getting behind the boards. This is the most common failure we see on additions built before 2015.
- Swollen or crumbling trim boards. HardieTrim is dense but not waterproof. When it’s installed too close to grade or behind a gutter that overflows, it wicks water and starts to expand. Once it crumbles at the corner, that’s a tear-out, not a patch.
- Paint peeling in sheets, not flakes. If the ColorPlus finish is separating from the board itself, that’s usually a factory finish failure or an installation issue with improper flashing. Repainting alone won’t fix it. The board needs replacement.
- Gaps where the addition meets the original house. This is a structural transition problem. Fort Lauderdale homes shift on sandy soil, and if the addition wasn’t properly tied to the main structure, the siding at that junction opens up. That gap lets in both water and pests.
- Dark streaks below window sills and door thresholds. That’s not dirt. That’s tannin bleed from water soaking the fiber cement and leaching through. The flashing was either missing or wrong when the window was installed. The fix is pulling the siding, installing proper flashing, and replacing the stained boards.
See the difference
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AfterReplacement Cost & What’s Included
A full home addition or ADU in Fort Lauderdale runs $45,000 to $130,000, and that range reflects square footage, foundation type, and whether you’re adding plumbing and electrical. For a smaller addition of 300 to 500 square feet, expect the lower end. For a full ADU with a kitchenette and bath, the higher end. If the exterior is being clad in James Hardie siding, materials for a 1,500-square-foot exterior run $8,000 to $15,000 alone, depending on the profile and whether you’re using ColorPlus pre-finished boards or painting on-site.
Every quote we write is a line-item price before any work starts. That means the siding, trim, flashing, fasteners, labor, and disposal are all broken out. You’ll know the board count, the profile, and the color code before we order a single piece. If a wall gets opened up and we find water damage behind the siding, the change order is written and approved by you before we proceed. No surprises at the invoice. The 365-Day Done Right Promise applies to the entire addition or ADU: if something we installed fails within a year, we come back and fix it. Written, not verbal.
DIY or Call Us?
For the exterior portions of a James Hardie addition or ADU, don’t DIY. Fiber cement siding is heavy, requires specialized blades, and the fastening pattern is specific. Too many nails and the board cracks. Too few and it flaps in a hurricane. Too deep and the board face dimples. The silica dust from cutting HardiePlank is also a legitimate respiratory hazard, which is why we use dust-extraction saws. That said, there are things you can do yourself: check your seams and caulk joints each spring, keep sprinklers from soaking the siding, and trim back vegetation so boards can dry. If you see seam gaps or crumbling trim, call us at (754) 354-7423. We’ll come look, tell you what actually needs done, and put the price in writing.
FAQs
James Hardie siding carries a 30-year limited product warranty, and in Fort Lauderdale’s climate you can realistically expect 25 to 35 years before board replacement becomes necessary. The failure point is almost always installation-related: bad flashing, wrong fasteners, or improper clearance from grade. We see 20-year-old HardiePlank in good shape and 5-year-old HardiePlank that has to be pulled because someone nailed it wrong.
Yes, isolated board replacement and seam repair is a normal job for us. If the damage is limited to a few boards or one elevation, we match the profile, cut out the damaged section, and replace it. The challenge is color matching older finishes. ColorPlus panels fade slightly over a decade in Fort Lauderdale sun, so a brand-new board will not blend perfectly against sun-faded neighbors. We’ll tell you that upfront.
A 300 to 500-square-foot addition or ADU in Fort Lauderdale takes 8 to 16 weeks from permit approval to final walkthrough. The range depends on foundation work, the complexity of plumbing and electrical, and whether the city’s permitting office is moving quickly that month. We give you a written schedule before work starts, with live arrival times and photo updates throughout, so you always know what’s happening on site. Call (754) 354-7423 for a timeline specific to your project.
We keep common James Hardie profiles, trim, and backer board inventoried for the addition and ADU projects we run in Fort Lauderdale. That includes 6″ and 8″ HardiePlank exposures, 4×8 HardiePanel sheets, and standard HardieTrim widths. If your existing profile is a less common reveal or a discontinued line, we order it direct from our supplier, usually with a 3 to 5 day lead. The work either holds up or it doesn’t – we make sure it does.
Written by Luca Romano, Owner & Lead Contractor, Sawyer Remodel Fort Lauderdale at Sawyer Remodel Fort Lauderdale, serving Fort Lauderdale and nearby areas.
