Free written scope consultation - allowances, timeline, and change-order rules on paper before a single trade is scheduled
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Before
AfterUnilock Home Additions & ADU: The Campbell Owner’s Guide
Unilock pavers and retaining wall systems used in Campbell home additions and ADU projects typically run $45,000-$130,000 installed, depending on whether you’re extending a foundation, building a detached unit, or integrating outdoor living space with structural walls. We stock Unilock-compatible materials and can usually begin material staging within 48 hours of a signed scope. Most Campbell homeowners discover their Unilock system needs attention when settling cracks appear in a patio that was supposed to carry load, or when a retaining wall begins tilting after winter rains saturate the backfill behind an ADU-grade elevation change.
Which Unilock Models This Applies To
Unilock’s structural lines break into two categories relevant to Campbell additions and ADUs: the Wall system (Brisa, Pisa, RomanPisa, and SienaStone) used for grade changes and foundation-adjacent retaining, and the Paver system (Beacon Hill, Bristol Valley, Copthorne, Richcliff, and Thornbury) used for load-bearing patios, walkways, and integrated outdoor rooms. The critical compatibility point is the vertical-to-horizontal transition - where a wall system meets a paver surface, Unilock specifies different base depths and drainage aggregates that are not interchangeable between residential-grade and commercial-grade specs.
To identify your system, check the back-face stamp on retaining wall units (usually found on the hidden rear edge) or the edge-spacer profile on pavers - Unilock’s ADU-suitable lines use a 3/16-inch spacer lug, while thinner residential-only pavers use 1/8-inch. We source OEM Unilock through authorized distribution in San Jose, though for certain foundation-adjacent applications we specify Belgard or Techo-Bloc equivalents with higher PSI ratings - the decision is documented in writing before any material is ordered, per Clause 1 of the Haven Standard.
Signs Your Unilock Home Additions & ADU Is Failing
- Step cracks in the wall face or settling pavers near the foundation. Campbell’s clay-heavy soil expands and contracts with seasonal moisture shifts; if the base course was compacted to 95% standard Proctor (as Unilock specifies) but the geotextile fabric was omitted or punctured, fines migrate upward and create voids that show as vertical displacement.
- Efflorescence that returns after cleaning. White mineral deposits indicate water is moving through the wall matrix rather than draining freely - common in ADU retaining walls where the drainage aggregate was substituted with native soil to save cost.
- Pavers rocking under foot traffic that were previously stable. The bedding sand layer has washed out, usually at a downspout termination or where the slope was insufficient; Unilock calls for 1/8-inch per foot minimum, and Campbell’s winter sheet-flow can overwhelm shallower grades.
- Wall leaning toward or away from the retained soil. A tilt exceeding 2 inches in 4 feet indicates either inadequate embedment (Unilock requires 6 inches minimum for walls under 4 feet, 12 inches for taller ADU-grade structures) or a failed deadman anchor system.
- Gaps opening between cap units or along copings. Thermal expansion in Campbell’s 90-degree summer cycles against near-freezing January nights stresses rigid adhesives; Unilock’s flexible polyurethane cap adhesive has a 15-year rated lifespan in this climate, but cheaper substitutes fail in 3-5 years.
Before
AfterReplacement Cost & What’s Included
| Scope | Campbell Price Range | What’s Included |
|---|---|---|
| Partial paver reset (under 200 sq ft) | $3,500-$8,500 | Lift, regrade, recompact base, reinstall with new bedding sand |
| Retaining wall rebuild (under 4 ft height, 20 linear ft) | $8,000-$18,000 | Demolition, drainage correction, new aggregate, rebuild to Unilock spec |
| Full ADU hardscape integration | $45,000-$130,000 | Design, permits, excavation, structural base, Unilock materials, installation, documented photo record |
| Wall cap replacement only | $800-$2,500 | Remove failed caps, substrate prep, adhesive, reset with flexible jointing |
The range driver is almost always what we find when we lift the first course. A wall that looks like a cap-and-adhesive problem often reveals saturated, decomposed backfill that requires full excavation to 12 inches behind the face. We put the number in writing before anyone picks up a shovel - the price you sign is the price you pay, with signed change orders required for any additional work. Every Unilock installation carries our 365-Day Done Right Promise and a documented photo record showing base prep, drainage detail, and final compaction readings.
DIY or Call Us?
There’s a safe middle ground here. A homeowner can check the wall for plumb with a 4-foot level, verify downspout termination points, and photograph efflorescence patterns - all useful diagnostic steps that help us scope the work before we arrive. What goes wrong fast: excavating behind a retaining wall without understanding active earth pressure (the lateral force soil exerts when disturbed), or attempting to reset pavers over an uncompacted base without a plate compactor and proper lift thickness. We’ve rebuilt three Campbell ADU walls in the past eighteen months where the homeowner’s weekend project destabilized the entire elevation. The fix then costs 40-60% more than calling us first. If you’re seeing any of the five signs above, call (831) 704-1211 and we’ll walk through what you’ve found - estimates are free, and we bring a legal pad, not a sales pitch.
FAQs
In Campbell’s climate - wet winters, dry summers, moderate freeze-thaw - a properly installed Unilock wall should perform 25-30 years before significant intervention. We’ve found that walls with correct drainage aggregate and 12-inch clean stone behind the face routinely outlast those with soil backfill by a decade. Call (831) 704-1211 for an exact assessment of your wall’s condition - estimates are free.
Partial repair is possible when the failure is isolated to the top two courses, the cap system, or a single drainage point. Once tilting exceeds 2 inches or step cracks penetrate more than half the wall depth, replacement is more cost-effective than staged remediation that addresses symptoms while the underlying base continues to fail. We document both options in writing with line-item pricing before you decide.
A partial paver reset under 200 square feet typically takes 2-3 days including cure time for the bedding layer. A retaining wall rebuild runs 5-10 days depending on excavation access and whether we’re coordinating with an active ADU foundation pour. Full home addition or ADU hardscape integration scales with the building permit timeline - in Campbell, we typically see 8-14 weeks from permit submission to final inspection when we’re managing both trades.
We stock common base materials, drainage aggregate, and geotextile on our trucks; Unilock-specific color blends and specialty units ship from San Jose distribution within 3-5 business days for standard lines, 2-3 weeks for custom orders. We do not begin demolition until materials are confirmed on-site - Clause 1 means no homeowner waits on back-ordered product with an open excavation. We also source KraftMaid, Cambria, and Silestone for integrated indoor-outdoor ADU finishes, quoted as a single written scope.
Rowan Construction Group Campbell is an independent contractor and is not affiliated with, endorsed by, or sponsored by Unilock Corporation. We install Unilock products according to manufacturer specifications and our own Haven Standard documentation requirements.
Ready to get a written price before any work starts? Call (831) 704-1211 to schedule your free estimate. We’ll review your site, identify the Unilock system in place, and deliver a flat-price quote with scope, timeline, and warranty in writing - the same way we’ve done it for over 4,000 projects since 2007. Measure twice, document once, build it right.
Written by Grant Rowan, Owner, Rowan Construction Group Campbell at Rowan Construction Group Campbell, serving Campbell and nearby areas.