James Hardie Garage Conversion Contractor in San Jose: What to Know First
We convert garages built with James Hardie siding and trim into legal, livable space across San Jose, and we do it as an independent James Hardie service provider, not a factory-authorized shop. A typical garage conversion in San Jose runs $95,000 to $180,000 for a full ADU build-out, with the James Hardie work itself (siding repair, trim replacement, weatherproofing before drywall goes up) usually landing between $4,000 and $12,000 depending on what’s failing. We give you a written price before any work starts, and that number doesn’t move unless you change the scope.
This page is for homeowners in San Jose whose garage has James Hardie siding, HardieTrim boards, or HardieBacker panels and who want to know what actually happens when that material meets a conversion project. If you’ve been burned by a contractor who quoted low and changed the price at the door, you’ll find the straight numbers here. Call (669) 266-4319 to schedule a free estimate.
How James Hardie Products Fail – and How We Fix Them
James Hardie fiber cement is tough, but it’s not invincible. After a decade of garage conversions in San Jose, here’s what we actually see on job sites, and what we do about it.
- HardiePlank lap siding wicking moisture at cut edges. Installers who cut HardiePlank with a dull blade or skip edge sealing leave raw fiber cement exposed. In San Jose’s wet winters, those edges absorb water and swell. On a garage conversion, we catch this before insulation and drywall go in. If the bottom courses are compromised, we pull them, seal the cuts, and rehang. If they’re sound, we seal and move on. You don’t want to bury wet siding behind a new wall.
- HardieTrim corners separating at the garage door opening. When a garage door gets framed into a wall with a window or French doors, the old trim corners often crack or pull away. We’ve seen this on nearly every attached garage conversion in the Willow Glen area where the original install used nails too close to the board edge. We pull the damaged HardieTrim, refasten with the correct spacing, and flash the new opening properly before the door unit goes in.
- HardieBacker boards crumbling behind failed tile work. In garages that had a utility sink or a bathroom rough-in, HardieBacker behind old tile sometimes turns to mush if water got behind the grout. The fix is straightforward: cut out the damaged section, check the studs, replace with new HardieBacker, and waterproof before re-tiling. Skipping this step means your new garage bathroom fails from day one.
- Improper clearances between Hardie siding and grade. James Hardie specifies a minimum clearance between siding and finished grade. When a driveway slab was poured too high years after the original siding install, water splashes up and rots the bottom edge. On a detached garage conversion, we regrade or add a drainage swale before touching the siding. The siding fix is simple. The drainage fix is what keeps it from coming back.
- Faded or chalked ColorPlus finish that’s still structurally sound. James Hardie’s ColorPlus baked-on finish holds up better than field paint, but after 15-plus years of San Jose sun, it chalks and fades. If the substrate is solid, we can repaint with a fiber-cement-rated exterior paint instead of residing. That saves thousands on a garage conversion budget, and it’s a legitimate fix if the boards aren’t cracked or swollen.
Our James Hardie Garage Conversion Contractor Process
Here’s how a James Hardie garage conversion job goes from first call to final walkthrough at Lodgewick ADU San Jose.
- 1
Call and site visit. You call (669) 266-4319, a live person answers, and we schedule a time to walk the garage. Russ Delmar or one of our project leads looks at the James Hardie siding, the slab, the roof, and the existing framing.
- 2
Written scope and price. We give you a written line-item quote before any work starts. It includes the James Hardie repairs, the framing, plumbing, electrical, insulation, drywall, and finish work. The price on that paper is the price.
- 3
Demo and structural work. We pull the garage door, frame the opening, and address any James Hardie repair work on the exterior before we close up walls. Exterior first, interior second. That’s the order that prevents buried problems.
- 4
Rough-in and inspections. Plumbing, electrical, and HVAC go in, and we pull permits with the City of San Jose. Inspections happen before insulation and drywall cover anything. No burying work that hasn’t been signed off.
- 5
Finish work and James Hardie exterior. Drywall, paint, flooring, and the exterior Hardie work get completed. We match existing siding profiles where possible, and we use OEM James Hardie stock for repairs unless a quality aftermarket equivalent makes better sense for the budget.
- 6
Final walkthrough and written guarantee. You walk the space with us. We hand you the written Kingswell Guarantee. If anything fails within 365 days, we come back and fix it. That’s in writing, on every project.
What James Hardie Garage Conversion Contractor Costs in San Jose
Here are honest ranges based on what we’ve quoted across San Jose. These are ballpark figures, not the price you’ll necessarily pay, because every garage is different.
- Full attached garage conversion to ADU: $95,000 to $180,000, depending on size, plumbing requirements, and finish level.
- Detached garage conversion with new exterior siding: $120,000 to $220,000 if you’re replacing the entire exterior with new James Hardie siding and trim.
- James Hardie siding repair on an existing garage before conversion: $4,000 to $12,000, depending on how many courses are failing and whether trim boards need replacement.
- HardieBacker replacement in a garage bathroom prep area: $800 to $2,500, mostly labor and waterproofing.
What moves the price: whether the slab needs leveling, whether the roof needs structural upgrades, whether the electrical panel has capacity for a new dwelling unit, and how much of the James Hardie exterior is salvageable. We’ll tell you which of those apply to your garage. Call (669) 266-4319 for a written quote. Estimates are free.
Why San Jose Homeowners Call Lodgewick ADU San Jose for James Hardie Work
We’ve been doing ADU work since 2010, and we’ve spent that time learning how James Hardie products behave in San Jose’s specific climate: wet winters, dry summers, and soil that shifts under slabs. We’re not authorized by James Hardie, but we’ve repaired enough of their siding and trim to know exactly where it fails and what it costs to fix right.
Every Lodgewick ADU San Jose project runs under The Kingswell Guarantee. Written price before work starts. Real arrival window. Clean job site at the end of every day. Written guarantee on every project, with a free return visit if anything fails within 365 days. That’s our 365-Day Done Right Promise, and it’s on paper before we drive the first nail.
We work with other ADU brands too, Abodu, Cover, and Dvele among them, because some homeowners want a prefab unit instead of a site-built conversion. When a prefab makes more sense for your lot, we’ll tell you. When your existing garage is worth converting, we’ll tell you that too.
Russ Delmar grew up in Los Angeles, trained in building technology at Los Angeles Trade-Technical College, and spent years working through every stage of a build before focusing on ADUs. He’s the one who ends up on the phone when a previous contractor left a half-finished garage conversion and a stack of permits that went nowhere. Tell me what you were promised before, and we’ll tell you what we can actually deliver.
FAQs
James Hardie’s product warranty covers manufacturing defects in the siding material itself, not installation or modification related to a garage conversion. The warranty generally stays intact for the siding as long as the product wasn’t damaged during the conversion. If we need to cut or remove siding to frame new openings, we document the condition and use proper cutting and fastening methods so the remaining product stays sound. If your siding has a separate installation warranty from the original contractor, that’s a different conversation, and we’ll walk you through it before any work starts. Call (669) 266-4319 if you want us to look at your specific warranty paperwork.
Yes, in most cases. HardiePlank lap siding is still manufactured in the same 5.25-inch and 8.25-inch exposures, and ColorPlus finishes are available in current stock colors. If your siding is an older or discontinued color, we’ll match it with a fiber-cement-rated exterior paint instead of leaving a mismatched patch. Matching texture matters too: smooth versus wood-grain, and we check that before ordering material. Call (669) 266-4319 and we’ll tell you if your exact siding is still available.
Most garage conversions in San Jose take 3 to 5 months from the day we start demo to the day the final permit is signed off. Permitting with the City of San Jose typically adds 4 to 8 weeks before construction, depending on plan review workload and whether your project triggers any zoning reviews. We handle the permits for you, and we’ll tell you upfront if your specific project is likely to hit delays. The Kingswell Guarantee includes a real arrival window for every phase, so you’re never left wondering when the crew shows up.
If the existing slab is level, the framing is sound, and the James Hardie siding is in decent shape, converting usually costs 30 to 40 percent less than building new. But if the slab has settled, the roof needs structural work, and the siding is failing across most of the walls, a teardown can be the cheaper option in the long run. We’ll give you honest numbers for both paths before you decide. A written quote covers each option, and you pick the one that makes sense for your budget.
If anything we built or repaired fails within 365 days, we come back and fix it. That’s the 365-Day Done Right Promise, and it’s in writing on every project. No arguing about who’s responsible, no chasing a subcontractor. You call (669) 266-4319, a live person answers, and we schedule the return visit.
Ready to Get a Written Price on Your San Jose Garage Conversion?
Call (669) 266-4319 to schedule a free on-site estimate. A live person answers, 24 hours a day, 7 days a week. We’ll walk the garage, look at the James Hardie exterior, and give you a written price before any work starts. No pressure, no vague numbers. Just a real quote from a contractor who puts every commitment on paper.
Written by Russ Delmar, Owner, Lodgewick ADU San Jose at Lodgewick ADU San Jose, serving San Jose and nearby areas.
