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Unilock Home Additions & ADU: The San Jose Owner’s Guide
Unilock home additions and ADU construction in San Jose typically run $53,100 – $153,400 depending on square footage, foundation work, and finish level. If you have a Unilock paver patio, walkway, or retaining wall that’s now sitting awkwardly against a planned home addition or ADU, we handle the full scope: design, permits, foundation, framing, and integrating your existing Unilock hardscape so it doesn’t get torn up and redone twice. Most San Jose owners discover the problem when their contractor starts quoting the addition and suddenly the patio you paid $15,000 for three years ago is in the way of the new foundation line.
We’re an independent remodeling company in San Jose, not a Unilock dealer or affiliate. What that means for you is simple: we spec Unilock products where they make sense, we know how their paver systems interact with new foundations and drainage, and we won’t sell you a product you don’t need just because it’s on a truck somewhere.
Which Unilock Models This Applies To
Unilock doesn’t make “home addition” or “ADU” products in the way most people think. Unilock makes hardscape: pavers, retaining wall blocks, and permeable paver systems. The connection to home additions and ADUs in San Jose is real but specific: if your existing property has a Unilock patio, driveway apron, walkway, or retaining wall, and you’re adding square footage, that hardscape either gets protected during construction or gets ripped out and relaid after the foundation cures. Both paths cost money. Both require someone who knows how Unilock pavers sit on their base layers, because a paver patio that’s pulled up and relaid on a poorly compacted base will settle and shift within two years.
The Unilock product lines we see most often on San Jose properties are the Brussels Block and Courtstone paver lines for patios and walkways, and the U-Cara multi-face wall system for retaining walls and planter boxes. Each has different joint widths, base depth requirements, and edge restraint needs. If you’re adding an ADU within five feet of a Unilock retaining wall, that wall becomes a structural consideration under San Jose building code, not just a landscaping feature. We check wall height, setback, and drainage before we ever talk about framing.
On the OEM-vs-aftermarket question: for pavers and wall blocks, Unilock products are the OEM. Aftermarket equivalents exist from Belgard and other manufacturers, but matching color, texture, and dimensional tolerance across brands rarely works well. If we’re extending an existing Unilock patio as part of a San Jose home addition, we order the same Unilock product line and lot-run whenever possible. Mismatched pavers look like a patch job, and you’ll see it every day for the next twenty years.
Styles & brands we work with
Signs Your Unilock Home Additions & ADU Is Failing
- Paver settlement around the existing patio perimeter. If the pavers nearest the house have sunk half an inch or more, water is running toward your foundation instead of away from it. In San Jose’s clay-heavy soils, this gets worse every wet season as the clay expands and contracts.
- Retaining wall leaning or bulging within ten feet of the planned addition. A leaning wall means hydrostatic pressure is building behind it. Add the excavation for a foundation and that pressure doesn’t have anywhere to go. The wall needs to be addressed before framing starts, not after.
- Drainage water pooling at the corner where your addition will tie in. If the downspout or area drain already can’t handle San Jose’s winter rains, adding roof surface from a new addition will overload it. You’ll see standing water within hours of a storm.
- Cracks in existing Unilock edge restraint or lifted border courses. Edge restraint failure is the first thing to go on a paver patio. Once the edge opens up, the whole field starts creeping. If your addition’s foundation trench runs alongside that edge, you lose the patio’s structural integrity entirely.
- Frost heave or efflorescence on wall blocks. San Jose doesn’t get much frost, but we do get cold snaps in the Almaden Valley and up toward the foothills. Efflorescence (that white chalky residue) means moisture is moving through the block. If the wall is part of your ADU’s landscape plan, the drainage behind it matters. Skip the fix and you get a cracked wall face within a few years.
See the difference
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AfterReplacement Cost & What’s Included
For a full home addition in San Jose, we quote $53,100 – $153,400 as a realistic installed range. ADU construction runs higher, $106,200 – $259,600, because it includes a second kitchen, separate bath, and utility connections. If your project is primarily about protecting or relaying Unilock hardscape while the addition goes in, the paver portion typically adds $4,130 – $12,980 to the job depending on square footage and whether we’re reusing the existing pavers or buying new Unilock product to match.
What drives the number up or down in San Jose: foundation type (slab vs. raised), soil condition, whether you’re in a hillside overlay zone that requires geotech reports, and how much of the existing hardscape can be salvaged. What’s included: the written scope, permit drawings, the build itself, permit inspections passed, and our 365-Day Done Right Promise on every job. That last part matters when you’re spending six figures. If something fails inside a year, we come back and fix it at no charge. It’s in writing before any work starts.
DIY or Call Us?
There are things you can do yourself safely. Walk the patio perimeter and mark any paver that’s moved more than a quarter inch. Check your downspouts and area drains during the next rain. Take photos of cracks and settlement and keep them with your house records. That’s useful, and it costs you nothing.
What you shouldn’t DIY: retaining wall demolition or repair within proximity to a foundation, any excavation that goes deeper than about a foot, and any paver relay work that involves edge restraint and base compaction. The risk isn’t just cosmetic. A botched base layer under pavers that sit next to your new foundation can redirect water into your crawlspace or slab, and that’s a $20,000 mistake dressed up as a Saturday project. Call (669) 274-2362 before you start digging. We’ll tell you straight up whether it’s a job for you or a job for us.
FAQs
Unilock pavers typically last 25 to 40 years in San Jose’s climate when installed on a properly compacted base with solid edge restraint. The paver itself rarely fails. What fails first is the base, edge restraint, or drainage around it. Fix those three things and the pavers will outlast your mortgage.
It depends on where your addition’s foundation line falls and how deep the excavation goes. If the foundation trench stays at least two feet from the patio edge, we can usually protect it in place with fencing and plywood overlays. If the trench runs alongside or through the patio, the pavers come out, get cleaned and palleted, and go back after the foundation cures. Reusing existing pavers is cheaper than buying new Unilock product, and we’ll tell you which path applies once we see the site. Call (669) 274-2362 for an exact read. Estimates are free.
A standard single-story addition in San Jose runs four to seven months from permit submission to final inspection. An ADU runs five to nine months depending on utility work and whether you’re doing a conversion or new construction. What slows most projects down isn’t the building. It’s the permitting, and San Jose’s planning department has its own timeline that no contractor can rush. We give you a written schedule with the written price, and we stick to the arrival windows we promise.
We order Unilock products per project because color lots and product runs vary. Stocking pallets of pavers we may not use for six months means color drift between what’s in the warehouse and what’s available when your project starts. We place the order once your permit is approved, and we coordinate delivery to the San Jose job site so the product isn’t sitting in the weather for weeks. If you need a specific Unilock line matched to existing work, we handle lot verification before anything gets delivered.
If you’re planning a home addition or ADU in San Jose and you’ve got existing Unilock hardscape in the mix, call (669) 274-2362 to schedule a free estimate. We’ll walk the site, explain what can be saved and what can’t, and hand you a written number you can hold us to. That’s the way we’ve done it since the Kingswell standard was set in 2004, and it’s the only way Trevor Nash runs a job. Give me the real problem and I’ll give you the real number.
Written by Trevor Nash, Owner, Penhallow Remodeling San Jose at Penhallow Remodeling San Jose, serving San Jose and nearby areas.
