Free written scope consultation - allowances, timeline, and change-order rules on paper before a single trade is scheduled
Unilock Home Additions & ADU: The Torrance Owner’s Guide
We install and build Unilock-compatible home additions and ADUs throughout Torrance, with full addition projects typically running $45,000 – $130,000 and ADU construction from $90,000 – $220,000 depending on square footage, foundation work, and finish level. Most Torrance homeowners call us after a paver course along an addition’s foundation line starts sinking, or when a retaining wall segment tied to an ADU pad begins leaning outward, usually because the original base wasn’t compacted to handle Torrance’s clay-heavy soil through wet winters. You’ll usually see the failure before you feel it: shifted pavers near the tie-in point, a widening gap at the wall-to-wall intersection, or water pooling against the addition’s footing after rain.
We’re an independent contractor, not affiliated with Unilock, but we work with their product lines every week and know how they behave in South Bay conditions.
Which Unilock Models This Applies To
Unilock’s product line splits into two broad families for addition and ADU work: their structural retaining wall systems (think Pisa, Brussels Dimensional, and U-Cara) and their paving lines (Estate, Courtstone, and Richcliff). Each uses different base-lock mechanisms. The Pisa and Brussels walls use a fiberglass pin system that locks each course into the one below it; the pins are model-specific and not interchangeable between the two lines. Courtstone pavers, by contrast, rely on side nibs and a tight sand joint, which means lateral movement shows up as a cascade of loose stones rather than a cracked wall face.
If you’re trying to identify what you have, look at the back face of a loose paver or the exposed back of a wall block. Unilock molds a small product code near the top edge. A missing code almost always means the paver came from their older Thornbury or Mattoni lines, both discontinued but still on plenty of Torrance driveways and walkways from early-2000s builds. Matching those requires color-sampling from the existing lot because their current equivalents run slightly lighter after years of sun exposure.
One compatibility gotcha worth knowing: Unilock pavers have a 3-5mm size variance allowance, which is normal, but mixing a new pallet with decade-old installed product creates visible gauge lines. For patios and ADU walkways where you’re tying new material to old, we sometimes pull replacement stones from less visible areas of the original installation and lay new product in the less prominent section. It keeps the color and wear line consistent where it matters.
Styles & brands we work with
Signs Your Unilock Home Additions & ADU Is Failing
- Paver courses near the addition’s foundation are sinking or separating. This is almost always a base-compaction issue. Torrance sits on heavy clay that expands when wet and contracts when dry. A base that wasn’t compacted in lifts, or that lacks proper drainage, will settle unevenly and leave visible dips along the foundation tie-in.
- Retaining wall segments tied to the ADU pad are leaning forward. The backfill behind the wall is pushing it. This starts as a slight lean you can only see with a level, but by the time it’s visible from across the yard, the wall’s structural pin connection has already begun to fail.
- Water is pooling against the addition’s exterior after rain. Unilock installations are only as good as the drainage behind and under them. If water no longer sheet-flows away from the structure, the sub-base is washing out from beneath the pavers or wall units, and the failure gets worse with every storm cycle.
- Gaps are widening at the corner where two Unilock walls meet. Properly installed Unilock wall corners become one monolithic structure. When you see a growing V-shaped gap at the corner, the aggregate base underneath has shifted, or the pins connecting the corner courses have sheared.
- You feel a slight bounce or movement when walking across pavers near the addition’s doorway. Pavers that move underfoot mean the setting bed has eroded and the stones are no longer holding each other in place. This is a trip hazard and a sign the area will need to be pulled, re-graded, and re-laid rather than spot-patched.
See the difference
Before
After
Before
After
Before
AfterReplacement Cost & What’s Included
In Torrance, a full home addition built with Unilock exterior elements runs $45,000 – $130,000. That range reflects the difference between a modest bedroom bump-out with a small paver walkway and a larger addition with stamped outdoor living space and a structural retaining wall. A detached ADU runs $90,000 – $220,000 here; City of Torrance ADU permit requirements, foundation engineering, utility tie-ins, and site drainage all move the number meaningfully. A garage conversion lands at $30,000 – $80,000 depending on whether you’re adding a bathroom and whether the existing slab needs leveling.
Every job includes a written line-item price before any work starts, so you know exactly what materials, labor, permits, and Unilock product costs. There are no verbal estimates that grow on the final bill. All exterior paver and wall work carries our 365-Day Done Right Promise, stated in writing with coverage terms, exclusions, and duration, starting from the completion date. If something fails within that year, we return and make it right at no charge.
DIY or Call Us?
You can safely check a few things yourself: look for visible settlement under the pavers, check whether water pools against the addition after rain, and run a level across the top of any retaining wall to spot a lean. Those observations help us quote accurately over the phone.
What doesn’t make sense to DIY is pulling up and re-laying Unilock product against a load-bearing foundation or structural wall. Retaining walls holding back soil are under constant lateral pressure, and a wall that’s been incorrectly rebuilt can collapse during the first heavy rain. The same goes for any wall segment over about waist height: the pins, the base, and the drainage all have to be right. That work belongs with a trained crew, and if a repair fails, you want someone who will come back free of charge, not a YouTube tutorial. If you’re not sure what you’re looking at, call us at (424) 337-6939. Isaac Pruett has spent two decades reading job sites like the ones along the Del Amo Fashion Center corridor, and he’s known for giving homeowners a straight answer before any tool gets picked up.
FAQs
Properly installed Unilock pavers can last 30 years or more in the South Bay, while structural retaining walls with good drainage often outlast the home they’re attached to. The failure point is rarely the Unilock product itself; it’s almost always the base, the drainage, or a shortcut during installation. In Torrance’s clay soil, a well-built base with proper drainage stone is the difference between a 5-year installation and a 30-year one.
If the settlement is limited to a small area, we can often pull and re-lay those pavers over a corrected base, which saves money. If the base failure has spread under a wide section, or the drainage pattern is wrong across the whole installation, patching just delays damage. We’ll tell you which one you have before you spend a dollar. Call (424) 337-6939 for an honest assessment.
A small paver repair or wall segment re-lay usually takes one to two days. Tying Unilock walkways and patios into a new ADU build runs concurrently with the structure’s timeline, not after it, so exterior work rarely extends the project. Once we inspect the site, you get a written schedule with the price. Call (424) 337-6939 to set up a free estimate.
We stock the most common Unilock replacement units, including Courtstone, Richcliff, and Brussels Dimensional wall blocks, along with the correct pins for Pisa and Brussels systems. For less common colors or older discontinued lines like Thornbury, we match from Unilock’s current offerings and quote the closest pairing before you approve anything. We also work across other professional-grade brands, including KraftMaid for cabinetry and Cambria and Silestone for stone surfaces, so an addition or ADU project doesn’t have to stop at the exterior.
You should know what’s happening in your home before anyone starts work. That’s just the job. Call Mason Remodeling Co Torrance at (424) 337-6939 for a free estimate on your Unilock addition or ADU project. A live person answers around the clock, and you’ll get a written price before any work begins.
Written by Isaac Pruett, Owner, Mason Remodeling Co Torrance at Mason Remodeling Co Torrance, serving Torrance and nearby areas.
