Frequently Asked Questions - ADU in Simi Valley, CA
We've been designing, permitting, and building ADUs in Simi Valley and across Ventura County since 2015. Below are the questions we hear most often, answered with the specifics we would want if we were researching a six-figure project.
Pricing & Cost FAQs
A detached ADU in Simi Valley typically runs $350 to $500 per square foot all-in, including design, permitting, and construction. A 500-square-foot one-bedroom unit usually lands between $175,000 and $250,000. Attached ADUs and garage conversions cost less because the foundation and utilities are already there. Site conditions matter a lot here: hillside lots in areas like Wood Ranch or Santa Susana can add grading and retaining costs, while flat parcels near the city center tend to hit the lower end of the range. Every Ellery ADU Studio project is quoted in writing before we start, under Clause 1 of the Haven Standard.
Our flat price includes architectural design, structural engineering, Title 24 energy calculations, the full permit set, all city fees, construction, and finish materials. What it does not include are items the homeowner typically wants to choose themselves: flooring upgrades beyond standard LVP, custom cabinetry, or premium fixtures. Site work beyond 30 feet of utility trenching, septic upgrades (rare in Simi Valley but relevant for some Santa Susana Knolls properties), and HOA compliance documentation are quoted separately if they apply. We itemize every line in the written estimate so you see where your money goes before you sign.
No. The Haven Standard's Clause 5, "No surprises," means the price we write is the price you pay unless you change the scope. We have seen other projects in Moorpark and Thousand Oaks where homeowners received a low initial bid, then faced change orders for "unforeseen" soil conditions or code upgrades. We avoid this by conducting a site evaluation before we quote, pulling the permit history from Simi Valley Building & Safety, and pricing known conditions into the original contract. If you later decide to upgrade finishes or add a deck, we write a new line item and you approve it in writing.
Simi Valley and Ventura County generally run 10 to 20 percent below comparable projects in the San Fernando Valley or West LA. Labor costs are lower here, and Simi Valley's permit fees are modest compared to Los Angeles Department of Building and Safety. That said, the savings shrink if your property sits on rockier terrain or requires extensive grading. We've built in both markets since 2015, and we can show you comparable project files from Calabasas and Simi Valley so you see where the differences come from.
Most homeowners use a HELOC, cash-out refinance, or construction loan. We do not originate loans, but we provide the detailed written scope and fixed-price contract that lenders require. Several Simi Valley clients have worked with local credit unions that understand ADU-specific appraisal methodology, where the future rental income can improve loan terms. We introduce you to lenders who have funded our projects before, and we answer their underwriting questions directly so you are not translating between us and the bank.
Service & Process FAQs
From signed contract to certificate of occupancy, most Simi Valley ADUs take 12 to 16 months. Design and engineering run 2 to 4 months, Simi Valley Building & Safety permit review takes 3 to 5 months (faster than LA County but slower than some smaller Ventura County jurisdictions), and construction runs 6 to 8 months depending on weather and finish complexity. We have had garage conversions in the Ranch House area finish in 10 months, and hillside projects in Big Sky take 18. We give you a written schedule with milestones before we start, and we text updates at each phase.
You meet with Nadia Ellery or a senior designer for a site evaluation and feasibility study. We measure your property, check setbacks against Simi Valley's zoning code, and identify utility locations. Within two weeks we return with preliminary floor plans and a ballpark price. Once you approve the direction, we produce the full construction documents, engineer the structure, and submit to the city. After permit approval, our build team takes over with the same project manager who designed it. One contract, one price, one point of contact. This matters because the ADU projects that fail are almost always the ones where the designer and builder can each blame the other.
Yes. We pull the building permit, the electrical permit, the plumbing permit, and any grading or environmental clearances your site requires. We attend every inspection, from foundation to final, and we correct any items the inspector flags at our cost. Simi Valley Building & Safety uses a specific checklist for ADUs that differs from standard residential; we have worked with their inspectors since 2015 and know what they look for at each stage. You receive copies of every passed inspection report and the final certificate of occupancy.
Usually yes, especially for detached ADUs where the work happens in your backyard. For garage conversions, you lose garage access for 6 to 8 months, and for attached ADUs there will be periods of shared-wall work that create dust and noise. We sequence the project to minimize disruption, and we protect access to your main dwelling. Homeowners in neighborhoods like Sycamore Glen and Indian Hills have stayed through entire projects; those with infants or home offices sometimes rent temporarily during the final finish phase. We discuss this in the feasibility meeting so you can plan.
Check your property's zoning on the City of Simi Valley website, confirm your lot size and existing home footprint, and gather any survey or plot plan from your original purchase. If you have a homeowners association, request their ADU policy in writing; some HOAs in West Hills and Calabasas impose design restrictions beyond city code. Also note any easements, mature trees you want to keep, or slope conditions. The more you bring to our first meeting, the more precise our preliminary price can be.
Brands & Parts FAQs
We offer both, depending on your timeline, site access, and design goals. Stick-built gives maximum flexibility for custom layouts and matches existing architecture precisely. Prefabricated units from manufacturers like Dvele or Mighty Buildings can cut construction time by 30 to 50 percent and reduce on-site waste, which matters on tight lots in areas like Simi Valley's downtown core. We evaluate your property for crane access, foundation requirements, and utility tie-ins before recommending either path. The price is fixed either way, and the warranty is identical.
For prefabricated options, we have installed Dvele units with their integrated smart-home systems, and we have used Mighty Buildings for their fire-resistant 3D-printed panels on hillside sites where traditional framing faces wildfire code challenges. For stick-built projects, we source lumber, windows, and mechanical systems through standard trade channels, specifying brands like Andersen, Milgard, or Carrier based on performance and availability. We do not mark up materials; our contract shows you our cost plus a fixed management fee. If you have a brand preference, we accommodate it within the written scope.
Yes, with conditions. Homeowner-supplied items must arrive on site before their installation phase, and they must meet California Title 24 energy requirements and Simi Valley's plumbing code. We have had clients in Moorpark and Agoura Hills source custom tile or vintage lighting; we coordinate delivery and inspect for damage before installation. If a homeowner-supplied item fails, we document the condition when we received it and the installation method we used, per Clause 4 of the Haven Standard. Our labor warranty still covers our work.
Licensing & Insurance FAQs
Yes. Every pro working under our name is required to hold the California contractor license and insurance that state law requires for ADU construction. The local business is independently owned and operated, with Nadia Ellery leading the Simi Valley branch. The Haven Standard, which governs how we document and deliver every project, comes from Ellery ADU Studio's national framework. You can verify any contractor's license at cslb.ca.gov; we provide license numbers on request.
We carry general liability and workers compensation coverage as required by California law. Before construction begins, we provide a certificate of insurance naming you as additional insured for the project duration. This protects you if a worker is injured on your property or if construction damage occurs to a neighbor's land. We have maintained continuous coverage since opening this branch, and we renew annually. If your lender or HOA requires specific coverage limits, we can adjust the certificate to meet their requirements.
We pull all permits as the licensed contractor of record. The permit application lists Ellery ADU Studio as the responsible party, which means we answer to the inspector, not you. This is how it should be: if a plan check correction is needed, we handle the revision and resubmission. Homeowners who pull their own permits become the responsible party and assume liability for code compliance. We do not recommend this for ADUs, which involve structural, electrical, plumbing, and energy code compliance that crosses multiple disciplines.
Emergency & Response FAQs
Call us at (820) 444-6584. The phone is answered 24/7 by a live coordinator who connects you with the local team. For urgent issues like a water line break or exposed electrical, we dispatch the trade responsible that day or the next. For non-urgent concerns like finish selection changes or schedule questions, your project manager responds by the next business day. Every concern is logged in our project documentation system, per Clause 4 of the Haven Standard, so there is a record of what you reported and when we resolved it.
We focus on ADUs we designed and built, where we know the structural and utility layout from our own documentation. For emergency situations on other structures, we refer homeowners to qualified local contractors in our network. Our documentation system, part of the Haven Standard, means we can often diagnose and resolve issues faster on our own projects because we have photos, readings, and as-built drawings from every phase. If you purchased a home with an existing ADU and need assessment, we offer a paid feasibility and condition evaluation.
We correct it at our cost and resume work. This is rare because we have built in Simi Valley since 2015 and know the current code interpretations, but inspectors sometimes flag items that were not visible at plan check. If the stop work relates to a condition we could not have reasonably known, such as undocumented prior construction we discovered during excavation, we document it with photos, explain the finding to you in writing, and quote any additional work before proceeding. Clause 5 of the Haven Standard governs: no surprises, ever.
Warranty & Guarantees FAQs
We provide a written one-year workmanship warranty on all construction, with extended manufacturer warranties on materials and systems we install. Roofing typically carries 20 to 30 years, windows 10 to 20 years, and mechanical systems 5 to 10 years depending on brand. The warranty is transferable if you sell the property within the coverage period. We document the installation with photos and readings at completion, so if a claim arises, we can verify whether the issue stems from our work, a product defect, or homeowner maintenance. Call (820) 444-6584 to schedule your free estimate and receive the full warranty document.
The Haven Standard is our documented promise on every project: a written price before we start, a named project manager, verified crews, photo and reading documentation at each phase, and no scope creep without your written approval. Clause 1 is the written flat price. Clause 2 is the schedule window with text notifications. Clause 3 requires licensed, insured, background-checked crews. Clause 4 is the evidence: photos and readings of what we found and what we did. Clause 5 is no surprises. Since 2015, Ellery ADU Studio has delivered 900-plus ADUs under this standard, every one with a documented record when we left.
We address it. Before final payment, we conduct a walkthrough with you using a written punch list. Items you identify are scheduled and completed, then re-inspected with you present. After final payment, the one-year workmanship warranty covers any defects in our installation. We have had homeowners in Thousand Oaks and Chatsworth request minor finish adjustments; we schedule them and document the resolution. Our goal is that you would recommend us to a neighbor in Simi Valley or Moorpark, and we treat the warranty period as part of the project, not an afterthought.
Call (820) 444-6584 or request through our website. A live coordinator will connect you with Nadia Ellery's team for a site evaluation, typically scheduled within one week. We bring a measuring kit, a zoning reference for Simi Valley's current ADU ordinance, and preliminary design options based on your lot configuration. You receive a written feasibility summary and ballpark price within two weeks, with no obligation. Estimates are free because we believe you should know the real cost before you commit to any design work.
Written by Nadia Ellery, Owner at Ellery ADU Studio Simi Valley, serving Simi Valley and Ventura County since 2015.
Still Have Questions?
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(820) 444-6584