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Unilock Home Additions & ADU: The San Francisco Owner’s Guide
A Unilock home addition or ADU in San Francisco typically runs $53,100 – $153,400 as an installed project, depending on square footage, foundation work, and whether you’re attaching to the existing house or building a detached unit. Most San Francisco homeowners book a detailed written quote within a week of calling, with design and planning taking longer than construction itself. The symptom picture varies: some owners call us because a patio or retaining wall built with Unilock pavers is settling and they want to know if it affects a planned addition; others are ready to break ground on an ADU and need someone who understands how Unilock paving integrates with a new foundation, drainage, and the access paths around the unit.
If you’re researching this page, you likely already have Unilock product on your property, or you’re planning an addition that will include it. Either way, the critical unsexy truth about Unilock work in San Francisco is that the pavers themselves rarely fail. What fails first is almost always what’s underneath them: the base, the drainage, or the edge restraint. That’s where a home addition project can go sideways if nobody checked the existing Unilock installation before framing begins.
Which Unilock Models This Applies To
Unilock makes a broad range of paving and wall products, and the compatibility question depends on what’s already installed and what the addition will touch. In San Francisco, we most often see three product families on older homes: the Estate and Richcliff paver lines for driveways and walkways, Brussels Block for patios, and the U-Cara or Rivercrest wall systems for retaining and garden walls. Each has different joint widths, thicknesses, and base requirements, and you cannot assume a Richcliff paver will sit flush against a U-Cara wall without a transition detail.
Here’s the compatibility gotcha most owners never hear: Unilock products are not interchangeable across all series, even when they look similar. A 60mm Brussels Block and a 60mm Richcliff stone have different dimensional tolerances and surface textures. If we’re tying a new ADU walkway into an existing patio, we won’t just match color and size. We’ll check the installed date, the original base spec, and whether that specific paver is still in production. Unilock has changed manufacturing specs over the years, so a paver made in 2012 may not match a 2024 production run exactly.
For the addition itself, Elmstead Remodeling San Francisco is an independent general contractor, not a Unilock dealer or affiliate. We specify and install Unilock-compatible paving and walls as part of our home addition and ADU projects, and we can source product through local Bay Area supply yards that stock Unilock. When an existing installation needs patching or extension work, we’ll evaluate whether OEM Unilock product is available or whether a quality equivalent from our local yard makes more sense for a seamless visual match.
Styles & brands we work with
Signs Your Unilock Home Additions & ADU Project Has a Problem
Here’s what we find on San Francisco properties before, during, and after an addition or ADU build. These symptoms are all things we see regularly on our job walks:
- Settling pavers near the proposed addition. This usually means the original base was too thin or wasn’t compacted properly. In San Francisco’s sandy, shifting soils and hilly lots, a 4-inch base that worked in a flatter climate often isn’t enough. If pavers slope toward the house, water is being directed at the future foundation.
- Paver separation around the perimeter. When edge restraints fail or were never installed, pavers drift apart. This is common on older Unilock driveways in the Sunset District, where seasonal moisture and vehicle weight push the outer rows outward. The wide joints then let water into the base, accelerating the problem.
- Standing water on the Unilock surface after rain. San Francisco gets enough winter rain that a flat spot on a Unilock patio or walkway becomes a persistent puddle. The fix is usually a localized base correction and re-slope, not replacing the pavers, but it has to happen before you pour a new foundation or the water keeps finding its way to the lowest point: your new structure.
- Crumbling or cracked Unilock wall units near a planned addition. Wall units don’t typically crack on their own in San Francisco’s mild climate. When they do, it’s usually because the wall was built without proper drainage behind it, and hydrostatic pressure built up during wet winters. If you see bulging or cracked units, that wall needs attention before any excavation work happens upslope or downhill from it.
- Weeds and ants moving through the paver joints in large numbers. This may not sound structural, but it’s a reliable early indicator that the joint sand has washed out and the base beneath is being disturbed. It matters for ADU work because an ADU’s foundation area often abuts existing paving, and a compromised base adjacent to new concrete can lead to differential settlement at the connection point.
See the difference
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After
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After
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AfterReplacement Cost & What’s Included
For a home addition or ADU project that includes Unilock paving, walls, or both, here’s what to budget in San Francisco:
- Home Addition (attached, including any Unilock surface work): $53,100 – $153,400
- ADU Construction (detached, full build): $106,200 – $259,600
- Garage Conversion (with Unilock approach paving): $35,400 – $94,400
What drives the range on a San Francisco job: lot slope and access, soil conditions (parts of the city sit on fill, which affects foundation design), permit and review timelines with the Department of Building Inspection, and the square footage of Unilock paving that needs to be installed or corrected. A flat Sunset District lot with easy alley access costs less than a hillside Noe Valley lot where materials have to be staged down a set of stairs.
Every quote we write includes the line-item cost of materials, base work, labor, and disposal before any work starts. The written price is the price. If we find a hidden condition during excavation, we stop, explain what we found, and provide a written change order before proceeding. The 365-Day Done Right Promise applies to every completed project: if it’s not done right, we make it right.
DIY or Call Us?
If you have an existing Unilock patio, walkway, or driveway and you’re planning an addition, there are things you can safely check yourself. Walk the surface after a rain and note where water pools. Look for pavers that rock under foot. Check the outside edges where paving meets lawn or planting beds. These observations give us useful information on the first visit.
But here’s the part to be careful about: foundation-adjacent excavation, base compaction, and wall work near a structure you’re about to build on are not weekend projects. San Francisco’s soil movement, property line setbacks, and seismic requirements mean the work has to be done to a standard that holds up over decades. A failing wall or poorly compacted base next to a new ADU is a five-figure correction later.
What we’d suggest is calling us before you buy anything, break ground, or even finalize the addition’s footprint. We’ll walk the existing Unilock work, tell you honestly what can stay, what needs correction, and what the budget looks like. Tell me what the room needs to do, and we’ll figure out the rest from there. You can reach us at (831) 480-4497.
FAQs
How long does Unilock paving last in San Francisco?
Unilock pavers and walls, when installed with proper base and drainage, typically last 25 – 40 years in San Francisco’s climate. The pavers themselves are the most durable part of the system; the base and edge restraints are what determine whether you get 20 years or 40. We also stock compatible materials from partners like KraftMaid, Cambria, and Silestone for the interior finishes of ADU projects, so the full build stays under one roof.
Can failing Unilock paving be repaired instead of replaced?
Yes, in most cases. If the pavers themselves are intact, we can lift the affected area, correct the base, re-compact, and re-lay the same pavers. Replacement is only necessary when pavers are cracked, faded beyond a reasonable match, or a previous repair used a different paver that now stands out. Call (831) 480-4497 for an exact quote, and estimates are free.
How long does prepping or replacing Unilock work take before an addition starts?
A localized paver correction or edge repair typically takes one to three days. Full re-paving of a driveway or large patio area in San Francisco usually takes three to five days, including excavation and haul-off. We’ll give you the timeline in writing with your quote so you can plan around it.
Do you stock Unilock pavers and wall units?
We don’t warehouse Unilock product, but we source it through Bay Area supply yards that stock current Unilock lines. For matching older installations, we may need to order specific colors or sizes, which adds a few days to the schedule. We’ll check availability before you commit to anything.
Will the price change once work starts?
No, not without your written approval. We give a written price before any work starts, and that’s the price. The only exception is if we uncover a hidden condition – like a failed base that wasn’t visible before excavation – and in that case we explain what we found, show you what it means for the budget, and get your sign-off before proceeding.
Written by Graham Stein, Owner, Elmstead Remodeling San Francisco at Elmstead Remodeling San Francisco, serving San Francisco and nearby areas.
