Fast, Reliable New Detached ADU Across Burlingame
A new detached ADU in Burlingame typically costs $320,000-$520,000 all-in, from the first survey through final inspection, with most projects taking 10-14 months depending on tree protection requirements and foundation type. The single biggest variable on this side of the Peninsula isn’t square footage: it’s whether the City of Trees ordinance pulls your lot into arborist review, which happens on nearly every pre-1960 bungalow lot in the flats. Our New Detached ADU team plans for that review from the first site visit, because we’ve learned that guessing at it later is how schedules die. If you’re weighing a backyard ADU west of El Camino or up in the Easton Addition, call (971) 497-2402 and we’ll walk the lot with you before you spend a dollar on drawings.
Why Ellery ADU Studio Is Burlingame’s Preferred New Detached ADU Company
Burlingame homeowners come to us for a specific reason: our permit sets don’t get bounced back for tree protection gaps. The city’s building counter is known locally for flagging trench routes that cross root protection zones of protected street trees, and we’ve sat through enough of those conversations to know exactly what the arborist reviewer asks for before we ever submit. Our Burlingame clients get a written price before any work starts, under Haven Standard Clause 1, and that price already accounts for the arborist report, the tree protection plan, and the foundation redesign most lots here need. We don’t quote a bare slab and then act surprised when the oak in the back corner changes everything.
Nadia Ellery founded this studio in 2015, the year California’s ADU permitting landscape shifted, and she’s built the practice around a single contract that holds design, permitting, and construction to one written scope. That matters in Burlingame because the designer-versus-builder blame gap is where tree-related redesigns get expensive. Here, one team owns the whole thing. Burlingame homeowners regularly tell us the same thing: they’d talked to contractors who quoted a price, then came back after the arborist review with a foundation change and a higher number. Our written price holds, and if the finished ADU doesn’t match the permitted drawings, the 365-Day Done Right Promise means we fix it, in writing, before the project starts.
Every project also gets a documented photo record on every visit. You’ll see the trench before it’s backfilled, the pier forms before concrete, the panel before drywall. Not a summary of how the work felt. Evidence of what was done. That’s the standard we hold in Burlingame, and it’s why our local reputation leans on word of mouth from homeowners on Broadway and in Lyon Hoag.
Our New Detached ADU Services in Burlingame
If you’re adding a detached unit in Burlingame, the question isn’t whether we can build it. It’s whether the design survives contact with the city’s tree ordinance and the marine-layer humidity. Here’s how we approach the four paths we see most in this area.
Custom Built ADU
A custom detached ADU in Burlingame gives you a structure that fits a 50×125 lot without fighting it. Most lots in the flats can accommodate an 800-1,000 square foot one- or two-bedroom unit, but the foundation has to be chosen around existing root zones, not after the drawings are done. We typically specify pier-and-grade-beam or post-and-pier foundations on canopied lots west of El Camino, which keeps the protected oaks, redwoods, and sycamores intact and avoids the stop-work orders that slab-first designs invite here. A written price for a custom 1-bed in Burlingame runs $340,000-$470,000, including the tree protection plan, the permit set, and the construction.
1-Bed & 2-Bed ADU
The 1-bed and 2-bed detached ADU is the most common build we do in Burlingame because it fits the lot geometry and the rental math. A 1-bed, roughly 500-700 square feet, typically runs $320,000-$410,000 here; a 2-bed at 800-1,000 square feet lands between $440,000 and $520,000. Both numbers assume the lot triggers arborist review, which is the safe assumption anywhere west of El Camino Real. The price also includes the panel upgrade and lateral work we know Burlingame’s older bungalows need, because leaving those out of the first quote is how a clean permit becomes a failed rough-in.
Prefab ADU Installation
Prefab and modular systems work well in Burlingame, but only if the site work is planned around the tree canopy from day one. We specify and coordinate systems from Cover, Dvele, and Mighty Buildings within our single contract, which means the factory-built shell doesn’t become someone else’s problem at the foundation line. A prefab 1-bed in Burlingame, installed on a pier-and-grade-beam foundation with a documented tree protection plan, runs $300,000-$390,000 depending on the factory spec and site conditions. The shell arrives with the wind-load rating already engineered; the foundation and utility runs are where Burlingame’s ordinance gets real, and that’s our work.
Studio ADU
A detached studio ADU, 400-500 square feet, is the most budget-conscious path in Burlingame, but it’s still subject to the same arborist review as anything larger. Studios here typically run $270,000-$340,000. We’ve built them on Easton Addition lots where the setback and root zone only allow a compact footprint, and the pier foundation actually works in your favor: less excavation means less root disturbance and fewer arborist conditions on the permit.
What happens when you call
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A real person answersNo phone trees - you reach a local pro.
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You get an upfront price rangeHonest numbers before anyone is dispatched.
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A background-checked tech heads outLicensed & insured, dispatched right away.
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You approve before work beginsNothing starts until you say go.
Trusted Brands We Service in Burlingame
We coordinate prefab and modular shells from Cover, Dvele, and Mighty Buildings for Burlingame projects, and we keep the local parts issue simple: our crews work these systems regularly enough that a delayed connector or a missing anchorage kit doesn’t stall a foundation pour. Most Burlingame prefab builds use pier-and-grade-beam foundations, and we stock the hold-down hardware and vapor barrier materials those foundations require in this climate rather than ordering them from a warehouse in the Central Valley at the last minute. You get one contract, one written price, and one team accountable for the factory shell and the foundation underneath it.
Common New Detached ADU Problems We See in Burlingame Homes
- Tree-root conflicts discovered after the slab is drawn. A standard slab foundation on a canopied lot in the flats will almost certainly trigger a root zone conflict with the city’s tree protection ordinance. The late redesign to post-and-pier or grade-beam adds cost and pushes the schedule back months.
- Panel upgrade overlooked until rough-in. Burlingame’s 1920s-1950s bungalows commonly run on 100A service. A new detached ADU with a kitchen and laundry pulls more than that, and upgrading to 200A after the walls are framed means rewiring inside the new unit and a failed inspection on the record.
- Cast-iron lateral failure during trenching. Many pre-1960 lots here still have original cast-iron sewer laterals. Trenching for the ADU’s utility run crosses that lateral, and if it’s compromised, the city will flag it before you get your final. We scope it early and fold replacement into the written price.
- Marine-layer moisture trapped behind cheap cladding. Burlingame sits in a persistent marine-layer corridor, and humidity stays high most of the year. ADU shells here need rainscreen cladding and positive sub-slab drainage that a drier-climate contractor might call over-spec. It’s not; it’s what keeps mold out of a unit built a few blocks from the bay.
Pricing for New Detached ADU in Burlingame, CA
Here’s the range we quote in Burlingame, always as a written line-item price before any work starts:
- Studio ADU (400-500 sq ft): $270,000-$340,000
- 1-Bed ADU (500-700 sq ft): $320,000-$410,000
- 2-Bed ADU (800-1,000 sq ft): $440,000-$520,000
- Prefab 1-Bed, foundation-through-finish: $300,000-$390,000
Every one of those numbers includes the arborist report, the tree protection plan, the permit set, and the foundation type that actually works on your lot. What it doesn’t include is a surprise at rough-in. On a 1920s Spanish Colonial lot west of El Camino, our site plan for a 1-bed detached ADU shifted from a slab to a pier-and-grade-beam foundation after the city’s arborist flagged a mature redwood’s root zone crossing the proposed trench. We pulled the permit with a tree protection plan that included root pruning limits and fenced exclusion zones, then coordinated with the building counter to reroute the electrical lateral outside the protected area, keeping the tree intact and avoiding a stop-work order. That’s the difference between a quote built for Burlingame and a quote built for anywhere. Call (971) 497-2402 for a free, written estimate. We’ll give you a number before you pay us anything.
We Also Serve Cities Near Burlingame
Our crews work regularly in San Mateo, San Bruno, Belmont, and South San Francisco, so if you’re just outside the Burlingame line, the same arborist-first approach and written-price standard apply. The tree ordinance here is stricter than what neighboring cities enforce, which means our Burlingame clients get the most conservative site planning in the county. If you’re in one of those nearby markets, call (971) 497-2402 and we’ll tell you honestly whether your lot faces the same review.
Serving Burlingame, CA - Our Local Coverage Area
We’re based in the Burlingame area and know this community well. Use the map below to see our service coverage - if you’re nearby, we can almost certainly help.
FAQs - New Detached ADU in Burlingame
Yes, if the foundation excavation or utility trench falls within the protected tree’s root zone, the city will require an arborist review and usually a formal tree protection plan before the permit is issued. That trigger is nearly universal on pre-1960 bungalow lots in the flats, where mature oaks, redwoods, and sycamores canopy most backyards. Our written quotes in Burlingame always assume the arborist step is required, so the line item is already there when you sign. Call (971) 497-2402 for an exact figure on your lot.
No, in almost all cases you’ll need a 200A upgrade. A detached ADU with a kitchen, laundry, and heating load will exceed what a 100A service can carry, and the city’s plan checker will flag it during permit review. We fold the panel upgrade and any cast-iron lateral replacement into the written price from the first quote, because discovering these after framing starts is the fastest way to blow both the budget and the rough-in inspection. Call (971) 497-2402 to get a written number that already covers it.
Burlingame’s exposure rating falls under Exposure C in the California Residential Code, which governs wind loads for structures near open water and bay-front corridors. A compliant detached ADU here needs engineering for uplift on the roof-to-wall connections, shear wall detailing, and anchor bolts that meet the local wind zone. Factory shells from Cover, Dvele, and Mighty Buildings are engineered to that rating out of the box; our custom builds carry it through the structural drawings in the permit set. A cheap quote that leaves out wind-load engineering won’t survive plan review, and it’s the kind of omission that shows up when the first marine-layer storm hits. Call (971) 497-2402 and we’ll walk you through what the rating requires on your specific lot.
Wherever the trench falls within a protected tree’s root zone, you’ll need an approved tree protection plan that shows exclusion fencing, root pruning limits, and often hand-digging protocols within the critical root area. On most canopied lots west of El Camino, that means the utility route gets pushed to the lot perimeter or along existing driveway lines to avoid the root zones entirely. We coordinate with the arborist and the building counter before finalizing any site plan, so the trench route is locked at permit time rather than discovered during a stop-work order. Call (971) 497-2402 for a site evaluation.
It often contributes to a lower premium, because the documentation shows the insurer an ADU built to current code with structural wind-load engineering, not an unpermitted or under-engineered addition. The tree protection plan and the foundation method both matter: a pier-and-grade-beam foundation that avoids root zone conflicts reduces the risk of soil movement claims, and the documented photo record proves the work was done as permitted. We provide the full permit set, the photo record, and the final inspection sign-off, which is what your carrier will actually ask for. Call (971) 497-2402 and we’ll make sure your project file is worth handing to an underwriter.
If you’re planning a new detached ADU in Burlingame, start with a written price that accounts for the trees, the wind, and the age of your lot’s utilities. Call (971) 497-2402 to schedule a free site visit and walk-through. We’ll give you a number before you pay us anything, and the number will match the permit you actually get.
Written by Nadia Ellery, Owner at Ellery ADU Studio, serving Burlingame since 2015.