A free site visit, a check of what your lot allows and a written, line-item price.
Get your free estimateADU Company in Simi Valley, CA
Adding an ADU in Simi Valley usually costs between $180,000 and $320,000 for a detached unit before site work, and the city’s ranch-heavy housing stock on 7,000+ square foot lots makes rear-yard placement the norm rather than the exception. Simi Valley’s ADU ordinance allows units up to 1,200 square feet and relaxes parking requirements near transit, which gives homeowners flexibility you won’t find in Thousand Oaks or Moorpark. Our crews know the local soil, the wind patterns, and the permit desk. Call (350) 238-1748 for a free, written estimate.
Why Simi Valley Homes Are Different
Most homes in Simi Valley were built between the 1960s and 1990s, and the dominant styles are ranch and Spanish designs that sit on generous lots. That lot size is the single biggest reason ADUs work so well here: a detached unit in the back corner of a 7,000 to 10,000 square foot lot often leaves the front yard completely untouched, which keeps neighbors happy and preserves curb appeal. Garage conversions are equally common because many older garages are oversized or detached already, meaning the structural shell is halfway there before we start.
The climate shapes the build. Simi Valley summers run hot and dry, so every ADU we quote includes serious cooling capacity and insulation in the walls and roof deck. Winters are mild but wet, so drainage and foundation waterproofing matter more than people expect. And the Santa Ana winds are real: construction scheduling gets adjusted around high-wind days, and roof tie-downs and window ratings have to meet wind-resistance standards that aren’t optional here. East of the 118, in older subdivisions, expansive clay soils often require deeper footings, and any builder who skips that step is setting you up for slab movement within a few years.
Our Main Simi Valley Services
Most Simi Valley homeowners come to us for one of three projects: a full home addition, a detached or garage-converted ADU, or a room addition. Here’s what each looks like in this city.
Home Addition Contractor in Simi Valley
A home addition in Simi Valley means extending your existing footprint, and the biggest local factor is setback rules. On the ranch lots west of the 118, we often see enough side-yard or rear-yard space to add 400 to 800 square feet without needing a variance, but every addition also has to respect the property line and any recorded easements. Wind-resistant framing and roof tie-downs add a few hundred dollars in hardware but keep the structure solid through Santa Ana season. Home Addition Contractor in Simi Valley.
ADU Builders in Simi Valley
Detached ADUs are the most common project type in Simi Valley because the lots can absorb them. The city’s allowance for units up to 1,200 square feet means a two-bedroom ADU with a full kitchen is realistic on most properties, and the parking reductions near transit routes remove a common dealbreaker. We quote both site-built and prefab options, including Abodu and Cover models, so you can weigh cost against construction timeline. ADU Builders in Simi Valley.
Room Addition Contractor in Simi Valley
A room addition usually means one new bedroom, a home office, or an expanded living space. In Simi Valley, these projects often convert existing covered patios or extend into the rear yard. The permit path is simpler than a full ADU because you’re not adding a separate kitchen or utility hookup, but the same foundation rules apply, especially east of the 118 where the clay soil demands deeper footings. Room Addition Contractor in Simi Valley.
What happens when you call
- 1
A real person answersNo phone trees - you reach a local pro.
- 2
You get an upfront price rangeHonest numbers before anyone is dispatched.
- 3
A background-checked tech heads outLicensed & insured, dispatched right away.
- 4
You approve before work beginsNothing starts until you say go.
Brands We Service in Simi Valley
We work with several prefab and modular ADU brands that fit Simi Valley lots and budgets well, including Abodu, Cover, and Dvele. Parts and cladding systems, including James Hardie, are sourced through our local supply chain to keep lead times predictable. See our brands page for the full list and what each system involves.
Pricing for ADU Company in Simi Valley, CA
| Service | Typical range in Simi Valley |
|---|---|
| Detached ADU (site-built, 400 – 800 sq ft) | $180,000 – $320,000 |
| Detached ADU (prefab, 400 – 800 sq ft) | $140,000 – $280,000 |
| Garage conversion to ADU | $95,000 – $180,000 |
| Home addition (400 – 800 sq ft) | $140,000 – $300,000 |
| Room addition (single room, 200 – 400 sq ft) | $65,000 – $140,000 |
| Kitchen expansion | $90,000 – $190,000 |
| Primary suite addition | $110,000 – $220,000 |
| Second-story addition | $220,000 – $400,000 |
| Foundation and site work (expansive clay, footings) | $15,000 – $45,000 |
| Permit and plan set fees | $8,000 – $25,000 |
What pushes the price up in Simi Valley is almost always the soil condition east of the 118, where expansive clay requires deeper footings and sometimes a soils report before we even pour, and the wind-rated roof and window requirements that add a few thousand dollars to materials. Every project starts with a written price delivered before any work begins, so those costs are on the table from day one, not buried in a change order later.
Neighborhoods We Serve in Simi Valley
We work across the entire Simi Valley area, and most of our projects are concentrated in the residential neighborhoods that have the lot sizes to support ADUs and additions. Response time for an estimate visit is typically within two to three business days depending on scheduling.
- Central Simi Valley
- West Simi Valley (Wood Ranch area)
- East Simi Valley (older subdivisions east of the 118)
- Santa Susana Knolls
- Big Sky and surrounding hillside communities
Service Area – Cities Near Simi Valley
While this page is focused on Simi Valley, our crews also serve the surrounding Ventura County communities. If you’re closer to Moorpark, CA, Newbury Park, CA, Fillmore, CA, or Somis, CA, you can reach us at the same number and we’ll get you the same written-price process.
Serving Simi Valley, CA - Our Local Coverage Area
We’re based in the Simi Valley 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 About ADU Company in Simi Valley
We typically schedule estimate visits in Simi Valley within two to three business days. The visit includes lot measurement, a look at access for equipment, and a conversation about your goals. Call (350) 238-1748 and a live person answers, day or night.
Simi Valley’s ADU review process is generally faster than neighboring cities because the ordinance is newer and the city moved to streamline ADU applications. Plan-set preparation is usually the longest lead item. We handle the permit package for you and walk it through the desk.
The price we put in writing before any work begins is the number you pay for the scope described in that document. If you change the scope, we price the change in writing before doing it. Nothing gets added to the bill silently. Call (350) 238-1748 to get your exact quote started.
What happens when you call
- 1A real person answersNo phone trees - talk to a local adu pro.
- 2You get an upfront price rangeHonest numbers before anyone is dispatched. No surprises.
- 3We come out and measureLicensed & insured, at a time that suits you - the visit and the quote are both free.
- 4You get the price in writingLine-itemed, yours to keep, and nothing starts until you say go.
What Simi Valley Customers Say
"They handled the drawings and the permit paperwork for us. All I had to do was pick the finishes."
- Rosa M."Straight answers on what we could and couldn't do on our lot."
- Edwin H."Insulated the walls and ceiling properly. It stays comfortable even in July."
- Tamika W.
