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Boral Home Additions & ADU: The San Antonio Owner’s Guide
If you’re planning a Boral home addition or ADU in San Antonio, the installed cost for a full addition runs $45,000 – $130,000, while a detached ADU typically lands between $90,000 and $220,000 depending on square footage, foundation work, and finishes. Most owners reach out to us because their existing build has stalled, an earlier contractor left framing or flashing incomplete, or the project failed inspection over how Boral materials were integrated with existing roof lines and slab edges. The frustrating part is rarely the Boral product itself. It’s the intersection details, the places where Boral panels meet Hardie siding, where the new slab ties into old plumbing, where the roof slope changes mid-span. Those are the joints that leak, crack, or fail a final walkthrough.
We’re an independent general contractor in San Antonio, not affiliated with Boral, but we do stock and install Boral-compatible materials across home addition and ADU projects. Written price before any work starts, drop cloths and shoe covers inside the house from day one, and a 365-Day Done Right Promise that outlasts the final walkthrough. Call (432) 233-0976 for a free estimate on your addition or ADU.
Which Boral Models This Applies To
Boral products used in San Antonio home additions and ADUs fall into three main families: Boral TruExterior siding and trim, Boral roofing tiles and underlayment, and Boral building products like their plywood sheathing and fascia boards. The TruExterior line is the one we see most on additions in this market because it handles the humidity swings of a San Antonio summer without cupping or buckling the way some wood composites do. Trim profiles come in 5/4 and 4/4 thicknesses, with smooth or wood-grain finishes, and the kicker for compatibility is that Boral trim requires specific fastener schedules and flashing details at the sill and head. Miss those and the warranty doesn’t travel with the project.
For ADUs, we frequently match Boral TruExterior trim to HardiePlank lap siding because both products carry manufacturer warranties families can verify by name. If you have an existing Boral install and you’re adding on, we match the profile and color, then write every material line into the scope of work before the first tool leaves the truck. That’s how I was trained at Los Angeles Trade-Technical College, and it’s how we still run every addition and ADU in San Antonio.
Styles & brands we work with
Signs Your Boral Home Addition & ADU Is Failing
- Trim swelling or paint peeling at the bottom edge. Water is wicking up through an unsealed cut end or a missing sill flashing. Boral trim resists moisture, but the cut edges still need sealing, and skipping that step voids the warranty.
- Gaps opening at corners or window heads. Improper fastening or the wrong fastener type. Boral requires stainless or hot-dipped galvanized nails at specific spacing. We’ve corrected corners in the King William Historic District where nails had backed out after two Texas summers.
- Visible cracking in the sheathing. Substrate movement or span issues. Boral sheathing should not crack under normal San Antonio wind loads. If it is, something moved behind it and the crack is the symptom, not the cause.
- Water staining at roof intersections. The place where an addition ties into an existing roofline is the number one failure point on any Boral addition. Flashing gets bent, step flashing gets skipped, and the first big thunderstorm finds it.
- Doors that stick in the new framing. Foundation or framing settlement. San Antonio’s clay soil expands and contracts, and if the slab wasn’t prepped right on an ADU, the whole structure tells you within two years.
See the difference
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AfterReplacement Cost & What’s Included
In San Antonio, a whole-home addition with Boral materials runs $45,000 – $130,000 installed. A detached ADU typically runs $90,000 – $220,000. Where your project lands inside that range depends on three things: square footage, foundation type (slab on grade is less than pier and beam), and whether we’re tying into existing plumbing and electrical or running new service. A garage conversion with Boral trim and a small bath tends toward $30,000 – $80,000.
Every quote includes the Boral product specified by name, all flashing and fasteners, labor, permit coordination, and a written scope of work. You get a line-item price before demolition starts and a photo of the cleanup before the crew leaves. No change orders added after the first day, no estimates that grow quietly. Our 365-Day Done Right Promise covers the full project. If it’s not done right, we make it right.
DIY or Call Us?
There are a few things a homeowner can check safely: look at whether the trim bottom edges are cut clean and sealed, see if gutters are draining onto the walls instead of away from them, and check for visible gaps at the roofline. That’s useful information when you call.
What you should not do is pull trim, open the furring strips, or rework a roof tie-in yourself. Working off a ladder at a roof intersection with flashing is not a weekend project, and getting the Boral fastener schedule wrong on a two-story addition in San Antonio creates liability you don’t want. This is the point where Graham Stein walks the site room by room and writes down what’s actually failing before a single board comes off. Call (432) 233-0976 and we’ll get you a free estimate for the repair or the full build.
FAQs
Boral products themselves are warrantied for up to 25 years depending on the line, but the lifespan in San Antonio depends on installation details, especially flashing and fastener choices. A properly installed Boral addition should look and perform well for 30+ years. The weak links are always the connections, not the material. Call (432) 233-0976 to have us look at yours.
Most often, the repair is a flashing, fastener, or sealing correction. Full rebuilds are rare unless there’s extensive rot in the framing underneath. We’ll write down exactly what needs to happen and give you the price before starting.
A single-room addition with Boral trim and siding typically runs eight to twelve weeks in San Antonio once permits clear. A full ADU with foundation, plumbing, and electrical usually takes four to six months. We schedule around your family’s quiet hours where possible and name the drop cloths, shoe covers, and cleanup steps before we start.
We maintain common Boral trim profiles and fasteners on the truck for repair work. For full additions and ADUs, we order project-specific quantities to match your existing profile, color, and texture. Since we also stock materials from KraftMaid, Cambria, and Silestone for kitchens and baths, we can bundle finish work into the same written scope. Call (432) 233-0976 for an exact quote – estimates are free.
Written by Graham Stein, Owner, Elmstead Remodeling San Antonio at Elmstead Remodeling San Antonio, serving San Antonio and nearby areas.
