Free written scope consultation - allowances, timeline, and change-order rules on paper before a single trade is scheduled
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AfterFast, Reliable Home Additions & ADU Across El Granada
Most homeowners in El Granada don’t realize they’re living inside the California Coastal Zone until a contractor breaks the news. That unincorporated status changes everything about a home addition or ADU here. A simple garage conversion in El Granada typically runs $30,000-$80,000, while a full detached ADU lands between $90,000 and $220,000 depending on foundation work, utility runs, and the coastal permit path your property requires. We’re Barrett & Sons Construction, and we’ve spent decades navigating the San Mateo County coastal review process that turns ordinary projects into bureaucratic marathons for contractors who’ve never worked the unincorporated coast. Call (877) 610-1318 and we’ll walk you through what your specific lot actually allows.
Why Barrett & Sons Construction Is El Granada’s Preferred Home Additions & ADU Company
We’re not a franchise and we don’t dispatch strangers. Tom Barrett started this company in 1998, and his sons run the crews that show up in El Granada. When you call, a live person answers, not a voicemail box. When you sign a contract, our 90-Day Done Right Promise is written on it: if something isn’t done right, Tom comes back and makes it right, one call.
What that means in El Granada specifically is that we’ve already pulled permits for work on Avenue Alhambra, Coronado Street, and the bluff-facing streets where the salt air eats standard hardware for breakfast. We know which lots still have the original 1908 platting boundaries and which were merged in the 1950s. We know that a coastal development permit for an ADU on a bluff-edge parcel needs a different erosion and drainage narrative than one tucked back near Quarry Park. That local knowledge isn’t something you can train a new hire on in a week. It’s built job by job, permit file by permit file, over years of watching what the County Planning & Building Department’s coastal reviewers actually flag.
Our Home Additions & ADU Services in El Granada
Our Home Additions & ADU team handles the full range of work you might be considering for your El Granada property.
ADU Design & Permitting
Building an ADU in El Granada is a two-track process: standard building permits plus a San Mateo County Coastal Development Permit. We handle both, including the coastal review narratives, drainage calculations, and the back-and-forth with county staff that drags out for months if you don’t know the workflow. The design phase typically runs $5,000-$12,000 depending on whether you’re adding a detached unit or converting existing square footage.
Garage Conversion ADU
A garage conversion is the most cost-effective way to add an ADU in El Granada because the county reserves the right to reduce or waive some setback requirements when you’re working within an existing footprint. Most garage conversions here run $30,000-$80,000. On older El Granada homes, the existing slab is often the wild card: many of the 1950s and 1960s slabs were poured without a vapor barrier, and with the constant marine layer moisture, you’ll need a moisture test before anyone frames a wall on that floor.
New Detached ADU
A new detached ADU in El Granada typically falls in the $90,000-$220,000 range. The cost swing comes down to foundation type (pier-and-beam versus slab), utility trenching, and whether your lot triggers coastal bluff-edge review. We spec hot-dipped galvanized or stainless hardware on every exterior connection because standard fasteners start showing rust bloom within two years of El Granada’s salt-heavy air.
Junior ADU & Interior Conversion
Junior ADU conversions inside an existing home are the most affordable path, often landing in the $45,000-$130,000 range for a well-finished unit with a separate entrance. These projects still require a coastal permit in El Granada, but the review tends to move faster because there’s no change to the building envelope. For homes with original single-pane windows and early Romex wiring, we often roll in the electrical and window upgrades as a single scope rather than treating them as two separate jobs.
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 El Granada
When we install windows or doors on an El Granada ADU or addition, we’re fitting brands you can look up yourself: Simonton, Ply Gem, and PGT are the ones we spec most often for coastal exposure here. PGT’s impact-rated windows earn their price when a winter storm drives rain sideways off the Pacific, and Simonton’s vinyl frames hold up better than wood in the constant marine layer moisture. We don’t install mystery brands off a van, and every material line item is on paper before work starts.
Common Home Additions & ADU Problems We See in El Granada Homes
El Granada housing stock has a personality all its own, and most of it was never built for full-time coastal living.
- Original single-pane windows that sweat and rot the framing behind them. The 1950s-1970s cottages that make up much of El Granada still carry original glazing, and the constant humidity means condensation forms on the interior side every morning. By the time you see water staining, the framing’s been wet for years.
- Untreated sheathing that’s delaminating within two to three winters. We’ve pulled siding on homes a few blocks from the bluffs and found standard OSB that you could crumble with your fingers. On any El Granada addition, we spec moisture-resistant ZIP System or plywood sheathing as the baseline, not an upgrade. Out-of-area crews who don’t know the micro-climate often learn this lesson the hard way, and the homeowner gets the warranty call two winters later.
- Steel fasteners and connectors corroding well ahead of schedule. Uncoated steel in El Granada’s salt-laden air rusts within a few years. When we frame an addition, every exterior connection is hot-dipped galvanized or stainless. It costs more upfront and it’s the only thing that survives this climate.
- Foundation settlement on the old 25-foot-wide parcels. Many of El Granada’s original lots were platted narrow and later merged, which means a home might sit on two different foundation types. We’ve seen additions built over the seam where an old perimeter foundation meets a newer slab, and the differential settlement cracks drywall within the first year. Any El Granada addition starts with a foundation assessment, not a framing crew.
Pricing for Home Additions & ADU in El Granada, CA
We Also Serve Cities Near El Granada
Our crews work the whole coastside and up over the hill. If you’re in El Granada or nearby Half Moon Bay, Hillsborough, Millbrae, or Burlingame, we can help with your addition or ADU. For interior work beyond additions, we also handle Kitchen Remodeling in El Granada and Bathroom Remodeling in El Granada as part of larger projects or standalone scopes.
Serving El Granada, CA - Our Local Coverage Area
We’re based in the El Granada 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 - Home Additions & ADU in El Granada
How much does a home addition or ADU cost in El Granada?
A home addition in El Granada typically costs $45,000-$130,000, while an ADU runs $90,000-$220,000 for a new detached unit and $30,000-$80,000 for a garage conversion. El Granada’s coastal permit requirement adds real cost compared to incorporated cities, since every project needs both a building permit and a San Mateo County Coastal Development Permit. We provide written line-item quotes with no change orders that aren’t on paper first. Call (877) 610-1318 for a free estimate.
Do you handle the coastal permit process in El Granada?
Yes, we handle the full San Mateo County coastal development permit process in El Granada, along with standard building permits and inspections. This is the part of the job that trips up contractors who mostly work in incorporated cities, where a room addition just goes through normal city hall channels. In unincorporated El Granada, you’re dealing with the county’s coastal review workflow, and we know which reviewers want erosion narratives, which ones flag drainage plans, and how to keep the file moving instead of sitting on a desk for months.
Will the price change once work starts on my El Granada addition?
Not without a written change order that you sign first. That’s our rule: every scope, every allowance, every price change arrives as a written change order before work happens. If the permit reviewer requires something we didn’t anticipate (and coastal review sometimes does), we bring you the number in writing, explain why, and let you decide before a single nail moves. We don’t spring surprise invoices at the end.
How long does an ADU or addition take to build in El Granada?
A typical garage conversion ADU in El Granada takes 4-8 months from permit submittal to final inspection, and a new detached ADU takes 6-14 months. The wide range is driven by the coastal permit queue, which moves slower than standard city permitting, plus weather windows dictated by the marine layer. We’ll give you a written schedule with milestones when you sign, and we’ll keep you posted as the county moves the file along.
Do you offer a warranty on home additions and ADUs in El Granada?
Yes. Every project we complete in El Granada carries our written 90-Day Done Right Promise: if it’s not done right, Tom comes back and makes it right, one call. For structural and material defects beyond that window, we stand behind the manufacturer warranties on every product we install, and we stock local parts so follow-up service doesn’t take weeks. Call (877) 610-1318 to schedule your free estimate.
Written by Tom Barrett, Owner at Barrett & Sons Construction, serving El Granada’s coastside homeowners with honest pricing and coastal-smart building practices since 1998.