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El Dorado Hills · Attached ADU
One shared wall, a full second home grown off your El Dorado Hills house.
An attached ADU runs off the side of your El Dorado Hills home — its own door, real kitchen, full bath — riding the foundation, the PG&E panel and the water line already on the lot.
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Attached ADU in El Dorado Hills — fast facts
City
El Dorado Hills
ADU type
Attached ADU
Contractor license
CSLB #1119373
Free estimate
(916) 677-9774
Last updated
Joined, not freestanding
What an attached ADU really is
An attached ADU shares exactly one wall with your existing El Dorado Hills house. That single wall is the entire line between this and a detached cottage sitting out across the slope. Everything past it is a real home — a private entrance off the side or rear, a working kitchen, a full bath, a bedroom a tenant reaches without walking through your living room. We build these so owner and renter never cross paths indoors. The hard part is structural. The new unit ties into your roofline, your foundation and that existing wall, and on a custom Serrano or Promontory home where the original build is already substantial, the tie-in is where the real money hides. Done right, you can't find the seam from the street.
Shares one wall; everything past it is fully independent
Private entrance, full kitchen, full bath, real bedroom
Ties into the existing roof, foundation and wall line
The wall between two homes
The shared-wall fire and sound assembly
Your shared wall stops being plain interior framing the moment two separate dwellings sit on either side of it. Code wants a rated separation then. Usually that's a one-hour fire assembly running floor to roof — correct gypsum layering, fireblocking at every penetration, and a sound-rated cavity so your tenant isn't living inside your television. People don't see this coming. On a high-end El Dorado Hills home we've opened a wall expecting clean studs and found a structural beam plus HVAC trunk lines that complicate the rating. So the existing side frequently needs work too, not just the new one. We draw the assembly on the plans, build it to the listed spec, and the El Dorado County inspector signs off on a wall that physically exists.
One-hour rated separation between the two dwellings
Sound-rated cavity so neither side hears the other
Existing wall often needs upgrading to hit the rating
El Dorado County permits
Permitting an attached ADU here
El Dorado Hills is unincorporated, so there's no city counter — your permit files through El Dorado County, which is a different animal than Sacramento or Placer next door, and honestly a slower one. Budget for that. Attached units also get an extra read in plan check, since reviewers study how the addition connects to your existing house. One county quirk bites people: El Dorado County wants the Title-24 energy documentation signed off before the slab pour, not after — so we sequence the energy approval ahead of concrete instead of chasing it later. We submit the site plan, elevations, the wall-tie and foundation details, full MEP and PG&E coordination as one package. Slope grading, granite, and any septic load surface right here too.
El Dorado County review — slower than Sacramento or Placer
Title-24 must clear before the slab pour, not after
Plan check scrutinizes the tie-in to the existing house
Shared utilities, real savings
Why the shared wall costs you less
The reason an attached ADU usually pencils cheaper than a detached one is sitting right in the name. You're tapping the foundation, the PG&E service and the water line already running to your house, instead of trenching a few hundred feet across a sloped El Dorado Hills lot to a freestanding cottage — through ground that's often decomposed granite or solid rock. One honest caveat: at 750 sq ft the County can require a separate water meter, and on bigger custom homes PG&E sometimes wants service work before adding a second kitchen's load. So we size the unit knowing where those lines sit. An attached unit also tucks into a tighter side yard than a detached build needs, which helps on a graded foothill lot where the buildable flat is limited. We've landed shared-utility attached projects in the low $200Ks.
Taps the existing foundation, PG&E service and water line
Cross the 750 sq ft line and a separate meter can apply
Fits a tighter side yard than a detached build needs
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Trusted by homeowners across Sacramento & surrounding areas.
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“Every ADU we build is designed to add long-term value and open new possibilities for your property. Let's build something great together.”
— Tim, ADU Specialist
Custom Designs
Built to fit your property & needs
Turnkey Process
We handle permits, plans & everything
Built to Last
Quality craftsmanship that stands the test
Financing Made Simple
$0 Down Options. Build Now, Pay Over Time.
You shouldn't have to drain your savings to build wealth. We partner with trusted ADU lenders to find financing that fits — many homeowners build with little to nothing out of pocket.
Home Equity (HELOC)
Tap your existing equity at competitive rates — the most popular way to fund an ADU.
Renovation Loans
Finance the build against your home's projected after-completion value.
ADU-Specific Financing
Specialized lenders who underwrite based on the rental income your ADU will produce.
Cash-Out Refinance
Roll the project into a new mortgage and keep one simple monthly payment.
Estimate Your Monthly Payment
See what financing your ADU could look like — and how rental income can help cover it.
$180,000Loan amount
Credit Score
Very good · 700–739
Estimated Monthly Payment
$1,320/mo
At 7.99% APR over 30 years (illustrative)
Often offset by $2,000–$3,500/mo in rental income
No prepayment penalties with most partners
Pre-qualification with no impact to your credit
Illustrative only — not a loan offer. Actual rates and terms are set by third-party lenders based on your qualifications.
Service areas
Where we build
Headquartered in the Greater Sacramento Area and serving homeowners from the Sierra foothills down through the Bay Area. Don't see your city? We probably still get there — just ask.
The most common things Sacramento homeowners ask before starting an ADU project.
An attached ADU shares one wall with your existing house. A detached unit stands alone out in the yard. That shared wall is the whole difference — it lets the new unit borrow your foundation, your PG&E service and your water line, which usually makes it cheaper than a freestanding cottage on the same El Dorado Hills lot. It also fits a narrower side yard, which matters on a sloped foothill parcel where the flat buildable ground is limited. Out here the demand actually leans detached and custom, because lots are big and budgets are high. But on a graded lot, or when you'd rather not trench utilities downhill through granite, attached is frequently the smarter call.
El Dorado County. El Dorado Hills is unincorporated, so there's no city building counter, and it does not run through Folsom or Sacramento County next door even though Folsom sits right against the western edge. Every ADU permit out here files through El Dorado County. Worth knowing up front: that county process tends to run slower than Sacramento or Placer, so we plan the schedule around it rather than promising you a Sacramento timeline. We handle the full submittal — site plan, elevations, the structural tie-in details, Title-24 and MEP, plus the PG&E coordination — as one complete package.
It's a real El Dorado County scheduling gotcha, and it's caught builders who don't work the county regularly. El Dorado County wants the Title-24 energy documentation signed off before you pour the slab — not after, the way some jurisdictions handle it. If you sequence it like a Sacramento job and pour first, you can stall the whole project waiting on energy approval with concrete already in the ground. We front-load the Title-24 clearance so it's done before the slab date. It's a small thing that turns into weeks of lost time if your contractor doesn't know to plan for it.
No. El Dorado Hills is PG&E territory, not SMUD, and not Folsom's municipal electric utility either — people mix all three up because the boundaries sit close together near the county line. That matters for how the service coordination and any panel or meter work get handled, since PG&E's process and timelines differ from the others. We've done enough PG&E coordination on the El Dorado County side to know the rhythm of it, so a second kitchen's electrical load doesn't blindside the schedule.
Quite possibly. El Dorado Hills is foothill ground — rolling terrain, slopes, decomposed granite, oak woodland, and granite shelves under a lot of these lots. That's the headline cost risk on any footing or plumbing trench out here. Hitting rock can mean real excavation, slower digging and heavier equipment. It's not a dealbreaker, it's a line item. The honest move is to expect it and price it before we bid, so the trenching number reflects the ground you actually have. Attached units help here, since you trench far less than a detached build would across a sloped lot.
Serrano's architectural review is strict, and it's the tightest design control of any community out here. Any exterior change goes through their committee, and they care about rooflines, siding, color, massing — all of it. The good news for an attached ADU is that we're matching your existing home anyway, so a unit detailed to disappear into the original house is exactly what a strict review board wants to see. We've dealt with HOA design review before. The move is to bring them a package that already respects the guidelines instead of fighting for variances. Marble Valley, Blackstone, Stonebriar and the other associations vary in how strict they run, but the approach is the same.
Often yes, but there's a step the sewer homes skip. Some of the larger and more rural El Dorado Hills parcels still run on septic, and an extra bedroom adds load to that system. The County has to be satisfied your tank and leach field can carry the added bedroom load before the ADU gets approved. Sometimes that means a system upgrade, an expanded leach field, or a soils review. We chase that question first, before anybody falls in love with a floor plan, because on the rural lots it can move both the budget and the timeline.
At and above 750 square feet the County can require a separate water meter for the ADU instead of letting it ride on your existing service. Below that, you usually share. We size the unit knowing where that line sits, so you're not tripping a meter requirement to gain twelve square feet you didn't actually need. PG&E may also want service or panel work before adding a second full kitchen's load — another reason to settle the utilities early instead of discovering them at framing.
That's the entire point of doing it right, and out here it matters more than most places because the homes are high-end and detailed. We match the siding or stucco, carry the elevation and trim lines across, and tie the new roofline into your existing roof so the addition reads as part of the original house. Someone driving through Promontory, Crown Village or the Town Center neighborhoods shouldn't be able to find the seam between the old house and the new unit. On a custom build that match is most of the craft, and in a strict-review community like Serrano it's also what gets the exterior approved.
Yes — the attached-ADU work and photos on this page come from real jobs we built and stand behind, including one over in Fair Oaks. We're based in Sacramento, about 30 minutes west, so El Dorado Hills is regular territory for us. We know the El Dorado County counter and its slower rhythm, the Title-24-before-slab quirk, the PG&E coordination, the HOA review and the granite excavation, because we've worked through them on real foothill lots rather than read about them.
Other services
Not quite the right fit?
Every Sacramento ADU project is different. Here are the other paths we build under one roof — and we're happy to talk through which one fits your lot best.
We treat every home like it's our own — quality work, clear communication, and happy homeowners.
PaulOwner · Future Generation
9 min read1,911 words8 sections
Building an Attached ADU in El Dorado Hills, El Dorado County
An attached ADU in El Dorado Hills borrows one wall from your existing house and makes the rest a separate, legal home — its own door, kitchen and bath. We're a Sacramento design-build contractor, license #1119373, and we build this exact thing across the region. What follows is how we think about attached units on El Dorado Hills' sloped foothill lots, where the granite, the HOA review and a slower county rewrite the math.
01Section
What "attached" actually buys you
The word attached carries real weight. It means your new unit shares precisely one wall with your existing El Dorado Hills house and is otherwise a complete, independent home — a private door off the side or rear, a real kitchen with its own range and sink, a full bath, and a bedroom a tenant reaches without ever crossing into your space. The shared wall is the only thing tethering the two homes. Everything else is separate living, on its own.
That single connection is why people pick attached over detached. You're not setting a freestanding cottage out on the slope and trenching utilities downhill to reach it — through ground that out here is frequently decomposed granite or solid rock. You grow off the house already standing, leaning on the foundation, the PG&E panel and the water line already there. El Dorado Hills runs the other direction from most of the region, though: this is the high end of the local ADU market, and demand leans heavily toward detached and custom guest-house builds because there's room and budget for them.
