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Unilock Home Additions & ADU: The Riverside Owner’s Guide
Unilock home additions and ADU construction in Riverside typically runs $90,000 to $220,000 for a complete detached accessory dwelling unit, while a garage conversion or room addition falls between $30,000 and $130,000 depending on square footage, foundation work, and finish level. You usually know it’s time when your current space no longer works – aging parents need a ground-floor suite, a grown child needs a private entrance, or the garage has become dead storage and Riverside rents justify the build. We’ve built enough additions across Riverside to know that Unilock pavers and retaining wall systems often become part of the scope, tying the new structure’s hardscape to the existing driveway and patio so the whole property reads as one piece.
We’re an independent contractor. We install and integrate Unilock products, but we’re not a Unilock dealer or manufacturer affiliate.
Which Unilock Models This Applies To
When an addition or ADU goes in, the Unilock conversation usually centers on three product lines: Hollandstone and Brussels Block for driveways and walkways that tie into the new entrance, Pisa II or Estate Wall for retaining walls where grade changes around the new foundation, and Beacon Hill Flagstone or Umbriano for patio surfaces that connect the main house to the ADU. Each series has specific dimensional tolerances – Hollandstone is a 60mm paver, Brussels Block runs 60mm and 80mm, and Estate Wall blocks have a lip system that locks courses together, which matters when you’re matching existing hardscape after excavation.
Two things trip up Riverside homeowners. First, Unilock colors vary by manufacturing batch. A “Sierra” pavestone poured in 2019 will not match a “Sierra” poured in 2025 perfectly, so if we’re extending an existing patio around a new ADU, we plan the color transition at a natural break line rather than promising a seamless blend. Second, older Unilock installations from the 1990s and early 2000s often used discontinued lines like Olde Greenwich Cobble. In those cases, OEM is gone and we source a quality matched equivalent rather than ripping out a whole hardscape. Curtis Lane has spent enough years matching pavers on Riverside additions to know when to blend and when to replace.
Styles & brands we work with
Signs Your Unilock Home Additions & ADU Is Failing
- Settling or sinking pavers near the new foundation. This usually means the subgrade wasn’t compacted correctly after the addition’s trenching, and water is now migrating under the base. You’ll see low spots within a year of the addition being completed.
- Retaining wall leaning or bulging. Behind that tilt is almost always hydrostatic pressure – Riverside’s clay-heavy soil holds water against the wall after winter rains, and without a proper gravel backfill and drain tile, the wall pushes outward. This gets worse every season.
- Gaps opening between the original structure and the addition. Different foundation types – slab on grade against raised wood framing – move at different rates through Riverside’s temperature swings. If the original contractor poured a rigid connection between them, you’ll see cracks.
- Joint sand washing out of paver seams after heavy rain. Riverside’s winter bursts of rain will flush polymeric sand if it wasn’t activated correctly or if the pavers are moving underneath. You’ll see weeds and standing water in the seams.
- Door and window alignment issues in the new ADU. When doors bind or windows won’t latch seasonally, it points back to foundation settlement. This isn’t a cosmetic issue – it’s a signal the structure is moving more than it should.
See the difference
Before
After
Before
After
Before
AfterReplacement Cost & What’s Included
| Scope | Riverside Installed Range |
|---|---|
| Detached ADU (400 – 800 sq ft, complete) | $90,000 – $220,000 |
| Garage conversion to ADU | $30,000 – $80,000 |
| Home addition (room/suite) | $45,000 – $130,000 |
| Unilock paver patio tied to addition | $3,500 – $11,000 |
| Retaining wall (Unilock block) | $4,000 – $10,000 per wall section |
These are real fixed-price ranges for Riverside, not estimates. What moves the number: foundation type (slab vs. raised), kitchenette or full kitchen in the ADU, utility trenching distance to the main sewer and electrical panel, and whether the city requires structural upgrades to the existing house. The written price we give you before work starts includes all permits, engineering, materials, labor, and the Unilock hardscape. It does not move at the door.
DIY or Call Us?
You can safely check a few things yourself: walk the paver line after rain and mark low spots with chalk, run a string line along the retaining wall to see if it’s out of plane, and note where water pools. That information helps you talk to any contractor and keeps you from getting talked into work you don’t need. What you should not do yourself is dig out and reset a retaining wall, level settled pavers that abut a new foundation, or attempt any structural work around the addition itself. Foundation corrections, drainage, and structural ties are not weekend jobs. Getting it wrong means redoing the whole hardscape and possibly compromising the addition. Call (424) 567-8472 and we’ll send a crew lead to look at it, give you a straight number, and put the scope in writing.
FAQs
A properly installed Unilock paver patio on a compacted base with polymeric sand joints will last 25 to 30 years in Riverside’s climate before the surface needs resetting, and the wall block itself has a manufacturer lifespan well beyond that. What fails early in Riverside is the installation underneath – poorly compacted base, missing geotextile, or skipped drainage. Those fail within 2 to 5 years. Call (424) 567-8472 for an assessment if your hardscape is under five years old and already moving.
Yes, if the failure is isolated – a section of settled pavers, one end of a retaining wall, or joint sand that’s washed out – we repair the zone, not the whole project. If the base was never compacted or drainage was never installed, patching just delays a bigger failure, and we’ll tell you that plainly before we take your money. The goal is a repair that holds, not a repeat visit.
A garage conversion in Riverside typically runs 10 to 16 weeks. A detached ADU runs 5 to 9 months depending on plan check at the city and utility work. We sequence Riverside jobs so that subs are booked in order and the schedule you get at contract is the schedule we hold.
We order Unilock pavers and wall block through our regular material accounts and have them delivered to the Riverside job site on our schedule. We don’t retail individual units from a yard, but if we’re already on your project and you need a few matched pavers to fill a gap, we’ll bring them on the truck. We also work with KraftMaid, Cambria, and Silestone for the interior scope so the whole project runs through one crew on one schedule.
Written by Curtis Lane, Owner, Bradford Remodeling Co Riverside at Bradford Remodeling Co Riverside, serving Riverside and nearby areas.
