Unilock Home Additions & ADU Nationwide | Barrett & Sons Construction

Unilock Home Additions & ADU: The Los Angeles Owner’s Guide

Unilock home additions and ADUs in Los Angeles typically run $53,100 to $153,400 installed, and we stock the hardscape components, base materials, and edge restraints that Unilock designs depend on. Most owners call us after the foundation settles, a retaining course shifts, or the original installer cut corners on the base layer and the pavers start moving. You’ll know it’s failing when doors stop latching at the new addition, cracks run diagonal from a window corner, or a paver course near the ADU foundation starts heaving after the first heavy rain.

Call (877) 610-1318

Barrett & Sons is an independent contractor, not a Unilock dealer or affiliate. That matters because we’re not trying to sell you a full repave when a base repair would do. We match the Unilock product line you already have, price the repair honestly, and give you the written scope before anyone swings a shovel.

Which Unilock Models This Applies To

Unilock’s residential paver lines that we commonly see under and around Los Angeles additions and ADUs fall into three groups. The most common are the U-Cara multi-piece wall system, the Mattoni and Brussels Block paver lines, and the newer Townstone and Promenade Plank products for patios and walkways. Each uses a different joint width, edge profile, and base depth recommendation, and mixing them is where most failures start.

The key identifier for matching a Unilock part: flip any loose paver and look at the underside. Unilock stamps a product code on most lines, and the color number is a two- or three-digit code printed on the original invoice or the unit label. Orange-tinted base sand that breaks apart in your hand is not a Unilock spec, that’s a generic paver sand, and it explains most paver shifting we repair. In Los Angeles, where clay-heavy soil expands and contracts with seasonal moisture swings, Unilock Edge Restraint or equivalent aluminum edge is non-negotiable. Without it, the outer course walks outward within two or three years.

For OEM versus aftermarket: Unilock pavers are matched by color, not just size. The same paver size from a different factory lot will look wrong against the original, and you’ll notice it every time you walk out the door. Aftermarket base and bedding material is fine when it meets the same gradation spec, but the top course needs to come from the same product line. We keep the common edge restraints, filter fabric, and angular base rock on our trucks, and we can typically match any Unilock color still in production within two days through local supply houses in Los Angeles.

Signs Your Unilock Home Additions & ADU Is Failing

• Diagonal cracks from window corners. This is settlement under the addition, and in Los Angeles it’s most often clay subsidence or a poorly compacted fill. The crack starts at the weakest point, which is the corner of any opening, and the fix is foundation-level, not a band-aid patch.
• Paver courses pulling away from the ADU slab edge. The edge restraint either wasn’t installed or was nailed into soil instead of set in compacted base. When the first course walks, every course behind it follows within a season.
• Standing water pooling against the new foundation. Grade was pitched wrong, usually flat or toward the structure. Over time, that keeps water against the slab, and in a city with our occasional heavy winters, it will find a crack to exploit.
• Doors that stuck once and now won’t latch at all. This is differential movement between the old structure and the new one. It’s not a hardware problem. Your addition is moving independent of the original house, and the header sill is taking the stress.
• Unilock caps working loose on a seating wall or stair. Mortar or adhesive failed, often because the installer used an acrylic adhesive not rated for the weight of a wall cap. Loose caps turn a seating area into a trip hazard pretty quickly.

Replacement Cost & What’s Included

Here’s the honest pricing structure for Los Angeles, as of this year. A home addition runs $53,100 to $153,400 depending on square footage, whether you’re adding a bathroom or kitchen, foundation type, and how much of the existing structure needs tying in. A detached ADU falls higher, $106,200 to $259,600, because it’s a separate structure with its own water, power, and sewer laterals, its own permit set, its own inspection train.

What drives the price more than anything on the low end is the unknown under the ground. You dig a footing and find a buried French drain from 1964, or a root system from a neighbor’s 70-year-old oak, and the concrete takes an extra two yards and a day. That’s a written change order, never a surprise at the end.

Included in our pricing: engineered plans when the permit requires them, permits pulled and inspections signed, all site protection, the full Unilock or matched hardscape scope when it touches the addition, hauling, and a written 90-Day Done Right Promise. We don’t price allowances that are convenient. We price the scope as we’d build it for our own place.

You won’t get a phone price that holds from a national outfit. You’ll get one from us: scope in writing, allowances in writing, change orders in writing, and a fixed line-item price you can take to any other bidder in Los Angeles and compare. Call (877) 610-1318 for the estimate.

DIY or Call Us?

You can safely reset a couple of loose pavers, sweep in new joint sand, and check that your downspouts are kicking water away from the addition. That’s good homeowner maintenance, and we’ll tell you exactly how if you call.

What we’d rather you not touch: anything involving a foundation under load, a shoring wall, gas or electrical rough-in inside the addition, or a seated wall that’s lost its structural glue. A paver is heavy. A collapsed shoring post or a broken gas line is a different kind of conversation, and not one any homeowner should have with an insurance adjuster. If the addition or ADU is moving, the sooner we look at it, the smaller the repair. Call (877) 610-1318 and tell us what you’re seeing. Tom or one of his sons will answer.

FAQs

Ready to Fix It? Call Barrett & Sons.

If your Unilock addition or ADU hardscape is moving, cracking, or walking outward, call (877) 610-1318 for a free estimate. Tom Barrett and his sons will come out, look at the base and the edge, and tell you honestly what it needs and what it costs, in writing, before anything gets started. We’ll do it right the first time, or we’ll come back and make it right. Proudly serving Los Angeles for over 29 years, with the permits pulled, the inspections signed, and the license number you can look up yourself.

Written by Tom Barrett, Owner, Barrett & Sons Construction at Barrett & Sons Construction, serving Los Angeles and nearby areas.