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Belgard Home Additions & ADU: The San Jose Owner’s Guide
Belgard home additions and ADU construction in San Jose typically runs $53,100 – $153,400 for a full addition, while a detached ADU built to Belgard hardscaping and exterior standards lands between $106,200 and $259,600. We handle the framing, foundation, utilities, and finish work, then tie the exterior into Belgard pavers, retaining walls, and permeable surfaces so the whole property reads as one build, not a patch job. Most San Jose homeowners call us after a handyman-grade addition starts showing its age: cracks at the roofline tie-in, settling at the slab edge, or a permit that never got closed and now blocks a sale.
Which Belgard Models This Applies To
Belgard doesn’t manufacture wall panels or roof trusses for additions. What Belgard produces is the exterior hardscape system: pavers, segmental retaining walls, permeable pavement, and outdoor living components like fire pit kits and grill islands. When an addition or ADU in San Jose is spec’d “Belgard,” it means the site work and exterior surfaces are built on Belgard products, and that’s where compatibility matters. The two product lines we see most on San Jose additions are the Belgard Catalina and Mega-Arbel paver series for driveways and paths, and the Belgard Diamond 9D and Dublin retaining wall blocks for grade changes at the addition’s edge. Here’s the gotcha: Belgard pavers are modular, but they’re not interchangeable across series. A Catalina paver is 60mm thick with a different edge profile than a Mega-Arbel at 80mm. If your addition settled and you need to match existing pavers, pulling a paver and measuring the thickness against Belgard’s spec sheet is the only way to order the right replacement without a visible seam. We keep a digital caliper on the truck for exactly that. For aftermarket versus OEM on retaining blocks, OEM Belgard is worth the premium. Aftermarket blocks rarely match the chamfer and color blend, and the difference shows at every course line.
Styles & brands we work with
Signs Your Belgard Home Additions & ADU Is Failing
- Cracking at the roofline tie-in. The addition roof was framed into the existing house without proper flashing or a structural saddle, and now thermal movement in San Jose’s hot summers and cool winters is opening a gap. Water gets in where the crack is widest.
- Settling at the slab perimeter. Belgard pavers around the addition start to lip or separate because the base material under them wasn’t compacted to spec, or the slab edge itself is sinking. In San Jose’s expansive clay zones, this shows up within two dry seasons.
- Sticking doors or windows inside the addition. The new framing is moving independently of the original structure. This isn’t seasonal humidity. It’s either a foundation issue or missing shear transfer at the connection point.
- Water pooling against the addition wall. Belgard permeable pavers are designed to handle drainage, but if the site wasn’t graded before the pavers went down, water backs up and sits. Over time that means rot at the sill plate and efflorescence on the retaining wall blocks.
- Building department red tag or unclosed permit. We get calls from San Jose homeowners trying to sell a house with an unpermitted addition or ADU. The work might have looked fine for years, but the planning department won’t sign off without structural verification and corrections.
See the difference
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After
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After
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AfterReplacement Cost & What’s Included
For home additions in San Jose, you’re looking at $53,100 – $153,400 depending on square footage, foundation type, and whether it’s a ground-floor bump-out or a second-story addition. ADU construction runs $106,200 – $259,600, with the spread driven by site work, utility trenching, and whether it’s attached or detached. Every number we give is a written line-item price before any work starts. That’s The Garrison Standard: no verbal estimates, no change orders that appear after the drywall is up. Here’s what those ranges include: demolition and disposal, foundation and slab work, framing to current California code, roofing and flashing at the tie-in, rough plumbing and electrical, insulation, drywall, flooring, and the Belgard hardscape work at grade. The 365-Day Done Right Promise covers all of it. If anything we built fails inside that year, we come back and fix it at no charge. Curtis Lane has it in writing on every contract, and you’ll have a signed copy before the first tool comes out.
DIY or Call Us?
There’s almost nothing on a home addition or ADU that’s safe for an owner to repair alone. The high-tension problems here aren’t garage door springs, but they’re just as unforgiving: a settling foundation, a roof that’s pulling away from the house, or gas and electrical rough-ins that were never inspected. Those are the things that hurt people or burn structures down. What you can safely do is document the failure. Take photos of the crack pattern, mark the date, measure the gap width if you can reach it safely, and check whether the permit history on your San Jose property shows a closed permit for the addition. Then call (669) 272-2637. We’ll walk you through what we’re seeing, give you a straight number, and schedule a site visit if the scope warrants it. Don’t open up a wall to look for the problem. That is how you turn a $500 flashing repair into a $5,000 remediation.
FAQs
A properly framed addition or ADU in San Jose should stand for 50 years or more with normal maintenance, and the Belgard paver and retaining wall components typically carry a transferable manufacturer warranty that covers structural failure for the life of the product. In San Jose’s climate, the failure points we see before year 10 are almost always tied to water: bad flashing, skipped base compaction, or grade that slopes toward the structure instead of away.
Yes, and most of what we see in San Jose is repairable. The exception is when the foundation has moved enough to compromise the framing, or when the original work was so far out of code that the cost of bringing it up matches the cost of a rebuild. We’ll tell you which one you’re in after a structural assessment, and that assessment is part of the free estimate. Call (669) 272-2637 to set one up.
A ground-floor addition typically takes three to five months from permit to final inspection. A detached ADU runs five to eight months because of the separate utility connections and site work. San Jose’s building department is faster than it was a few years ago, but plan check for structural additions still runs six to ten weeks on average. We pull the permits for you and the permit fees are in the written estimate, not a surprise line item later.
We don’t carry full pallet quantities on the truck, but we keep a running inventory of the most common San Jose Belgard series in our yard: Catalina, Mega-Arbel, Diamond 9D, and Dublin blocks. For a standard repair or a modest addition, we’re typically able to start within the week. For a full ADU build, we order the Belgard product by the pallet once the site work plan is approved and the quantities are calculated. Curtis Lane won’t order a single block more than the plan calls for.
If your Belgard home addition or ADU in San Jose is showing cracks, settling, or water problems, don’t wait until the rainy season makes it worse. We provide a written price before any work starts, a live person answers the phone around the clock, and every job closes with a clean site and a signed guarantee in your hand. Call (669) 272-2637 to schedule your free estimate. Straight number, written scope, done when we said done.
Written by Curtis Lane, Owner, Bradford Remodeling Co at Bradford Remodeling Co San Jose, serving San Jose and nearby areas.
