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Unilock Home Additions & ADU: The San Jose Owner’s Guide
If you’re planning a home addition or ADU with Unilock pavers and wall systems in San Jose, the installed project cost typically lands between $53,100 and $153,400 depending on square footage, foundation work, utility rough-ins, and the specific Unilock product line you’re building with. Most San Jose owners discover their planning stage fails when the existing concrete pad won’t support the Unilock base spec, or when setback requirements force a redesign. We handle Unilock-compatible site prep, base installation, and structural integration for additions and ADUs across San Jose, and we’ll give you a written price before a single tool comes out.
Bradford Remodeling Co San Jose is an independent contractor. We’re not affiliated with Unilock, but we work with their paver and wall systems regularly and we know how the Unilock base spec has to be adapted for San Jose’s clay-heavy soil and seasonal settling.
Which Unilock Models This Applies To
This page covers full Unilock paver and retaining wall integration for home additions and ADU projects, not a single replacement part. The Unilock product lines we specify most often in San Jose are the Hollandstone and Mattoni paver series for walkways and patio slabs, Brussels Block for driveways and heavier load areas, and Lineo Dimensional Stone for retaining walls and stair risers where the grade change matters. Each series has different base requirements. Brussels Block, for example, is rated for vehicular loads and needs a compacted aggregate base of at least 10 to 12 inches in San Jose’s expansive clay. Hollandstone is a pedestrian-load paver and can get away with 6 to 8 inches of base in most yards, but not on a driveway approach.
Here’s the compatibility gotcha most owners miss: Unilock pavers are manufactured with a spacer bar on the side of each paver, not a flat edge. That means joint spacing is built into the paver itself, and if you’re matching an existing Unilock patio with a new paver lot, the series and color mix have to come from the same manufacturing window or the color drift will show. Unilock colors shift subtly between production runs. When we extend an existing patio for an ADU, we pull a sample from the existing installation and match at the distributor level before we order, because the color stamped on the pallet label doesn’t always tell you the whole story in San Jose’s UV exposure. Over a decade of California sun, even sealed pavers lose some surface tone.
For OEM versus aftermarket: Unilock pavers don’t really have an aftermarket equivalent the way a furnace igniter or a garage door spring does. If you’re matching existing Unilock, you buy Unilock. There are generic concrete pavers that cost less, but they won’t have the spacer bar, the color blend, or the freeze-thaw and UV rating that Unilock manufactures for. In San Jose, where the real concern is sun fade and soil movement more than frost, the Unilock manufacturing consistency is what you’re paying for.
Styles & brands we work with
Signs Your Unilock Site Prep or Existing Hardscape Is Failing
Most addition and ADU projects in San Jose start with an existing patio, walkway, or retaining wall that has to tie into the new foundation. If your hardscape is failing, the addition will fight it from day one. Here’s what we see most often:
- Pavers sinking or heaving near the planned addition footprint. This means the existing base wasn’t compacted for San Jose’s expansive clay, and the subgrade is moving with moisture. You can’t pour a foundation next to a moving paver field and expect the joint between them to stay clean.
- Retaining wall leaning or bulging at the middle. Over time, San Jose’s winter rains saturate the soil behind walls built without proper drainage. The hydrostatic pressure pushes the wall out. A leaning wall next to a new ADU foundation is a structural problem waiting to happen.
- Paver surface flaking or spalling in patches. That’s usually a de-icing or moisture issue, but in San Jose it’s more often trapped moisture under a sealer that wasn’t breathable. If the existing patio has flaking pavers and you’re extending the same surface, you need to know whether it’s the paver or the sealer that failed.
- Gaps opening between the paver edge and a concrete slab or foundation. Unilock pavers expand and contract slightly with temperature. If the edge restraint was never installed or has failed, the pavers drift. When the new addition goes in next to that drifting edge, the problem gets locked into the design.
- Water pooling against the foundation after rain. San Jose gets its rain in a few big winter storms. If the grading slopes toward the house and the pavers sit below grade, water is being directed at the foundation. Before an addition or ADU goes in, that drainage has to be corrected with proper slope and drainage channels.
See the difference
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AfterReplacement Cost & What’s Included
For a full home addition or ADU in San Jose with Unilock hardscape integration, the installed price range is $53,100 to $153,400. That’s the range for the complete project: design and structural drawings, permits, foundation and framing, utility rough-ins, interior finish work, and the exterior hardscape tie-in including paver patios, walkways, and any retaining walls.
What drives the price within that range in San Jose:
- Square footage of the addition or ADU. More square footage means more foundation, more framing, more electrical and plumbing rough-in, more everything.
- Site conditions. San Jose lots vary from flat to sloped. A sloped lot in the hills requires more excavation, grading, and retaining wall work. Flat lots in the valley are simpler.
- Unilock product selection. Brussels Block costs more per square foot than Hollandstone, and Lineo walls are a premium product. The specific series and the depth of the base prep both affect the number.
- Utility work. An ADU with its own kitchen and bath requires sewer, water, and electrical connections. If the sewer lateral is old or undersized, the scope grows.
Every Bradford Remodeling Co San Jose project gets a written price before work starts. No change orders unless you approve them in writing. No numbers that move at the door. The 365-Day Done Right Promise covers the completed work for a full year: if anything Bradford installed fails within that window, we come back and correct it at no charge. The Unilock manufacturer’s warranty runs separately and covers defects in the pavers themselves.
DIY or Call Us?
If your Unilock hardscape is failing around the area where you want to build, there’s a safe level of site assessment you can do yourself: check the paver edges for drift, look for water pooling against the house after a rain, and inspect retaining walls for leaning. These are observations, not repairs. The actual fix, compacting a new base, resetting a wall with proper drainage, or grading a paver field away from a foundation, is not weekend work. Getting the base depth and compaction wrong in San Jose clay means the pavers move again within a year or two, and now you’ve spent money twice.
For the addition or ADU itself, this is structural work. Foundation forms, framing, electrical rough-in, and plumbing are not items to attempt without a licensed crew. The risk isn’t just to the project, it’s to the people living in the house. Call (669) 272-2637 and we’ll walk the site with you, put the scope in writing, and give you a straight number before anything gets started.
FAQs
Unilock pavers themselves typically carry a lifetime guarantee against manufacturing defects, but the installed system, base, edge restraint, and joint sand, has a real-world service life of 15 to 30 years in San Jose depending on drainage, load, and whether the base was built to spec. UV exposure fades the color over time, but doesn’t compromise the paver. Call (669) 272-2637 if you want us to look at your existing patio or walkway before you plan an addition around it.
Yes, in many cases individual pavers or a section of pavers can be lifted and reset on a corrected base, especially if the failure is localized settlement or a failed edge restraint. If the base was never properly compacted across the whole field, you’re band-aiding the problem. For a project tied to a new addition or ADU, the base has to be right. Call (669) 272-2637 and we’ll tell you which situation you have after a site visit, and put the repair scope in writing.
The paver and retaining wall work for a typical San Jose addition or ADU site takes 5 to 12 working days, depending on the size of the paver field and whether new retaining walls are part of the scope. This usually happens after the structure is up and the utilities are in. The full addition or ADU project runs months, but the hardscape portion is a shorter, concentrated phase. We’ll put the schedule on paper before work begins, and the written price includes the timeline.
We order Unilock pavers and wall systems specifically for each project from the local distributor, matched to the exact series and color blend required. We don’t keep a yard full of pallets, because storing pavers in San Jose’s sun and rain before installation can cause color and moisture issues. For matching an existing Unilock installation, we pull a physical sample first. Call (669) 272-2637 and we’ll handle the match and the lead time as part of your written estimate.
Written by Curtis Lane, Owner, Bradford Remodeling Co at Bradford Remodeling Co San Jose, serving San Jose and nearby areas.
