A free site visit, a check of what your lot allows and a written, line-item price.
Get your free estimateFast, Reliable Home Addition Contractor Across Simi Valley
Adding square footage to a Simi Valley home usually costs between $180 and $340 per square foot for a site-built addition, with most bedroom additions landing in the $95,000 to $165,000 range depending on foundation work, finishes, and what we find inside the walls. That last part matters more here than almost anywhere else in Ventura County. Simi Valley has thousands of 1960s and 70s ranch homes with original aluminum wiring, undersized framing, and past additions that were never permitted. Our job, before we ever sign a contract, is to figure out what the house is hiding so the price you approve is the price you pay. Call (350) 207-2506 and we’ll walk you through it.
Why Benson ADU Ventura Is Simi Valley’s Preferred Home Addition Contractor Company
We’re not the contractor who shows up once, drops a verbal estimate on you, and goes quiet. Every Simi Valley project we take on starts with a written price, before any work starts. That’s part of The Relay Visibility Guarantee, and it’s stamped on every contract. Troy Eastman leads our team, and he’s the one you’ll talk to when something needs a straight answer.
Our crews work throughout Simi Valley regularly, from the flat central tracts off Los Angeles Avenue up into the hillside lots in Wood Ranch and Big Sky. We know the city’s permit reviewers, the wildfire-zone wall assembly requirements, and the way a 1970s ranch off Erringer Road tends to surprise you once drywall comes down. Dispatch and scheduling are coordinated from our brand’s Los Angeles office, and crews serve Simi Valley locally. We’re also part of the Relay Home Co. family, founded in 2006, and we back every job with a 365-Day Done Right Promise. If it’s not right within a full year, we make it right.
Bedroom Addition Contractor in Simi Valley
A Bedroom Addition Contractor in Simi Valley handles the design, structural work, permitting, and finish construction for adding a new bedroom to your existing home. Here, that typically means working with a ranch-style floor plan from the 1960s or 70s, tying a new roofline into an aging hip roof, and bringing the existing electrical and framing up to code before any new walls go up. For a standard 12×14 bedroom addition in Simi Valley, plan on $115,000 to $150,000 when the work includes a closet, new windows, drywall, insulation, and basic finishes.
Working With the Old Bones of a Simi Valley Ranch
Most additions we price in the east valley start with a careful look at what’s already there. Original aluminum wiring, 2×4 exterior walls with no shear strength, and roof rafters that don’t meet current span tables are common. We don’t ignore those. We write allowances into the contract for the fixes we can predict and price any surprise we find, in writing, before we touch it.
Permits, Title 24, and Fire Zone Code
A bedroom addition triggers a permit, and in Simi Valley that means the whole affected area gets reviewed against current Title 24 energy standards and the city’s high-fire-zone construction requirements. 1-hour exterior wall assemblies, ember-resistant vents, and fireblocking at every floor and ceiling penetration are standard. You’ll want a contractor who knows what the inspector in Simi Valley actually looks for.
Sunroom Addition in Simi Valley
A Sunroom Addition in Simi Valley gives you a glass-heavy living space that works beautifully with our climate, as long as it’s designed for the heat. With 90-plus degree summer days and occasional Santa Ana winds, a poorly insulated sunroom becomes a greenhouse. We size the glazing, ventilation, and roof insulation for exactly that, and we price sunrooms here between $55,000 and $110,000 depending on size, foundation type, and whether the room is conditioned space or a three-season porch.
Dealing With Sloped Backyards
In Wood Ranch and Big Sky, many backyards slope enough that a sunroom needs a stepped foundation or a short retaining wall. That’s not a dealbreaker. It’s a design decision we handle with a soil report and a hillside grading plan that passes Simi Valley Building & Safety the first time.
Waterproofing and Failed Flashings
We see a lot of older sunrooms in Simi Valley where the original flashing at the roof tie-in has opened up and water has been getting into the wall cavity for years. If you’re adding onto an existing sunroom, we’ll inspect that connection first. Rotted framing and failed waterproofing get fixed as part of the job, with a written change order before we open anything further.
Trusted Brands We Service in Simi Valley
We’re authorized to build with some of the most respected prefab brands in the industry, including Abodu, Dvele, and Mighty Buildings. For homeowners in Simi Valley who want a faster build with factory-controlled quality, these options can cut months off a traditional timeline. We stock the common components locally for our Ventura County jobs and source from these partners directly, so you’re not waiting on a supply chain or a middleman. Whether you go prefab or site-built, the written price and the 365-day guarantee stay the same.
Common Home Addition Contractor Problems We See in Simi Valley Homes
- Aluminum wiring from the 1960s and 70s. Most east valley tract homes were wired with aluminum branch circuits that are now a fire hazard under load. A bedroom addition means new circuits, and the old panel usually needs an upgrade too.
- Unpermitted past additions. We regularly find sunrooms and enclosed patios that were added without permits and don’t meet current beam or foundation standards. The city won’t sign off on new work until those are corrected.
- Roof rafters notched beyond code. In older ranch homes, plumbers and electricians in the 1970s notched rafters to run pipes and wires. Open the ceiling and you find structural weaknesses that must be reinforced with engineered trusses or sistered lumber.
- Hillside drainage failures. On sloped lots in Wood Ranch and Big Sky, poor original drainage sends water toward the foundation. Any addition on those lots needs a drainage plan that satisfies the city’s hillside grading review.
Pricing for Home Addition Contractor in Simi Valley, CA
Here are real numbers for the projects we price most often in Simi Valley. A bedroom addition on a central 1970s ranch runs $115,000 to $150,000. A sunroom addition runs $55,000 to $110,000 depending on glazing, conditioning, and foundation work. A bathroom addition runs $65,000 to $95,000. A bump-out, which extends an existing room by 3 to 5 feet, runs $40,000 to $75,000. Second story additions start around $225 per square foot and go up with structural complexity. The wild card on a 1960s or 70s home is the electrical and framing remediation inside the existing walls, and we handle that with allowances and a fixed-price change order process that you approve before we proceed.
| Addition Type | Typical Simi Valley Cost Range |
|---|---|
| Bedroom Addition (12×14) | $115,000 – $150,000 |
| Sunroom Addition | $55,000 – $110,000 |
| Bathroom Addition | $65,000 – $95,000 |
| Bump-Out (3-5 ft extension) | $40,000 – $75,000 |
| Second Story Addition | $225+ per sq ft |
We Also Serve Cities Near Simi Valley
Our crews work throughout the Conejo Valley and surrounding areas. If you’re in Moorpark, Newbury Park, Fillmore, or Somis, the same written pricing, background-checked crews, and 365-Day Done Right Promise apply. For homeowners searching for a Home Addition Contractor, our process is the same no matter which side of the 118 you’re on. And if you’re reading this from Simi Valley, we’ll be on site as soon as your approved scope is ready.
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 Home Addition Contractor in Simi Valley
Yes, in most cases. The city reviews the entire affected area, not just the new square footage. If the existing 2×4 framing, roof rafters, or foundation don’t meet current code, those elements must be reinforced or replaced before the city will sign off. We typically handle this with a pre-construction inspection and a written allowance so you know the range before we open walls. Call (350) 207-2506 and we’ll explain exactly what applies to your address.
We inspect the electrical panel and a sample of accessible wiring as part of every estimate. When we find aluminum branch wiring, cloth-covered romex, or an undersized panel, we include a line-item allowance in the written contract. During construction, if we open a wall and find a condition beyond the allowance, you get a fixed-price change order to approve before we proceed. Nothing gets billed without your signature.
Yes. Simi Valley sits in a designated high-fire-risk area, and the state’s wildfire building standards apply to additions. That means exterior walls need a 1-hour fire-rated assembly, eaves must be enclosed or built with ignition-resistant materials, and attic and crawl space vents need ember-resistant mesh. We spec these materials from the start so you don’t get a red-tag from Building & Safety mid-project. Call us for an exact quote on your fire-zone requirements.
Expect a soils report and a hillside grading review. Sloped lots need a foundation design that handles lateral soil pressure, often a stepped footing or a short retaining wall. Drainage from the hillside above the addition must be directed around the structure, not into it. We design for these conditions up front, which is why our foundation plans in Wood Ranch and Big Sky rarely come back from the city with corrections.
Yes. It’s one of the most common things we see in Simi Valley sunrooms, especially older ones where the original roof tie-in flashing has separated. We’ll inspect the wall cavity, replace any rotted framing, re-flash the connection, and then fold that repair into the written scope of your addition project. You approve the repair price before we open the wall further. Call (350) 207-2506 for a free estimate that includes the waterproofing inspection.
If you’re planning an addition on a Simi Valley home built in the 1960s, 70s, or 80s, get a contractor who knows what’s inside those walls before you sign anything. Call (350) 207-2506 to schedule your free estimate. We’ll put the price in writing and show you exactly what we found and how we’ll fix it.
Written by Troy Eastman, Owner at Benson ADU Ventura, serving Simi Valley homeowners with written-price additions and prefab ADU options.
