Unilock Home Additions & ADU Nationwide

Unilock Home Additions & ADU: The Walnut Creek Owner’s Guide

Unilock hardscape systems in Walnut Creek home additions and ADU projects typically run $45,000-$130,000 installed, depending on whether you’re integrating a paver patio, retaining wall, or permeable driveway system into the new footprint. We stock Unilock-compatible materials and can often begin procurement within 48 hours of a signed scope. Most Walnut Creek owners first notice trouble when settling cracks appear between the paver field and the new foundation, or when drainage from the addition backs up through the Unilock permeable base - both signs the hardscape wasn’t properly tied into the structural envelope.

Call (510) 686-6370

Which Unilock Models This Applies To

Unilock’s product lines for residential additions fall into three categories we regularly specify in Walnut Creek: the Beacon Hill Flagstone and Richcliff lines for patio and walkway integration; the Concord Wall and Brisa retaining systems for grade changes and planter beds; and the Permeable Paver series, including Turfstone and Eco-Priora, for ADU driveway and parking surfaces subject to Walnut Creek’s seasonal clay expansion.

To identify your exact product, check the chamfer edge profile and the spacer lug pattern on the paver underside - Unilock stamps a date code and plant identifier (Toronto, Buffalo, or the former Amherst facility) on every unit. The critical compatibility issue in Contra Costa County is freeze-thaw rating: pre-2018 Unilock units from the Buffalo plant sometimes carried a PSI rating of 8,000 rather than the current 9,500, which matters when tying into a foundation that will see structural load transfer. We source direct from Unilock’s western distribution in Stockton for current-spec material; for discontinued lines, we match color and compressive strength with Belgard or Techo-Bloc equivalents and document the substitution in writing before any unit is laid.

Signs Your Unilock Home Additions & ADU Is Failing

• Step cracking along the addition foundation joint. This happens when the Unilock bed wasn’t separated from the new stem wall with a compressible joint filler. In Walnut Creek’s Saranap neighborhood, we see this regularly on 2019-2021 ADU builds where the contractor used concrete sand instead of ASTM C33 washed bedding sand, allowing migration into the expansion gap.
• Pooling water on “permeable” surfaces after light rain. The joint aggregate has clogged with fine silt from the Diablo Range dust cycle, or the open-graded base was contaminated during construction. The system can’t drain what it can’t reach.
• Vertical displacement of wall units in a retaining structure. Usually indicates inadequate drainage behind the wall - a common shortcut on tight ADU setbacks where the builder didn’t want to haul out spoils. Hydrostatic pressure pushes the facing forward course by course.
• Efflorescence blooming across the field in irregular patches. Unilock’s coloring is integral, so surface whitening means soluble salts are migrating through the matrix. In Walnut Creek’s clay soils, this often traces to a high-sulfate soil condition that wasn’t tested before base placement.
• Loose or rocking pavers within two years of installation. The bedding layer was either over-compacted before screeding, or the paver was set directly on a concrete base without the specified sand setting bed - a “time-saver” that voids Unilock’s warranty and leaves the field vulnerable to point loading.

Before

After

Replacement Cost & What’s Included

Every quote is flat-priced with a written scope before work begins - Clause 1 of the Haven Standard. The price includes removal and disposal of failed material, base reconstruction to Unilock’s published installation detail, and a 365-Day Done Right Promise on workmanship. We pull permits where required by Contra Costa County and schedule inspection sequences so the hardscape isn’t buried before the building inspector signs off. No change to the scope proceeds without a signed change order, which is how we’ve kept projects within a few percent of the agreed number across 4,000-plus jobs since 2007.

DIY or Call Us?

What you can safely check: lift a loose paver and look at what’s underneath. Clean ASTM C33 sand should be visible, uniform in depth, and free of mud or organic material. If you see gray concrete residue or standing water in the base, the installation has failed and the fix is beyond surface relaying.

Where DIY goes wrong: retaining walls and permeable systems are structural elements, not cosmetic. A Concord Wall over 24 inches requires geogrid reinforcement designed to the surcharged load; get the embedment depth or grid length wrong and the wall leans within a season. Permeable pavers depend on an exact aggregate gradation - swap in local quarry rock that doesn’t meet the void-ratio spec, and the system fails to drain while still looking correct on the surface. We don’t recommend homeowners excavate behind retaining walls or operate plate compactors on open-graded stone without training - the equipment and the collapse risk aren’t trivial.

Call (510) 686-6370 and we’ll schedule a free estimate. We bring a documented photo record of what we find, a written price before any work starts, and the material spec sheet for whatever we propose to install.

FAQs