A free site visit, a check of what your lot allows and a written, line-item price.
Get your free estimateADU Company in Monrovia, CA
Benson ADU Builders plans and builds accessory dwelling units, home additions, and room additions across Monrovia, CA. ADU work in Monrovia means working with an older housing stock, tighter lots near the foothills, and a city plan check process that rewards complete submittals. We put the full price in writing before any work starts, and every project carries our 365-Day Done Right Promise in writing. Call (903) 568-7222 for a free estimate, and we’ll walk you through what fits your lot.
Why Monrovia Homes Are Different
Most Monrovia homes were built between the 1920s and 1960s, which shapes how we approach additions and ADUs. The original electrical panels usually need an upgrade to handle a second dwelling, and we plan for that cost from the first conversation rather than letting it surface as a surprise change order. The historic districts north of Foothill Boulevard come with their own design review layers, which is where our team’s experience with prefab panel systems helps. Off-site fabrication keeps the on-site build window short, which matters when your neighbors are close enough to hear every nail gun.
Terrain matters here too. Homes in the northern pockets near Canyon Park and the foothills often sit on lots with real grade changes, which affects foundation work, drainage, and how a detached ADU is positioned for setbacks. A flat-lot design does not always translate to a sloped Monrovia lot, so we evaluate elevation before we ever quote a number. Summer heat in the San Gabriel Valley also drives insulation and glazing choices, particularly for ADUs that will be rented out year-round.
Our Main Monrovia Services
Monrovia homeowners usually reach out about two things: building an ADU in the back, or expanding the house itself. Each service has its own dedicated Monrovia page with specifics on scope and local conditions.
ADU Builders in Monrovia
Detached backyard units are the fastest path to rental income or a place for family in Monrovia. We build with prefab brands like Abodu, Cover, and Dvele, which shortens construction time considerably compared to fully site-built work. The tradeoff is lot coverage and setback rules, which we check against Monrovia’s current ADU ordinance before we recommend a unit size. See the full breakdown on our ADU Builders in Monrovia page.
Home Addition Contractor in Monrovia
A home addition attaches to the existing structure and usually means a new foundation, roof tie-in, and expanded mechanical systems. In Monrovia’s older homes, we often find knob-and-tube wiring or cast-iron drain lines that must be replaced as part of the project. That is exactly the kind of thing we name in the written price up front rather than burying in a change order. Pricing and scope details live on our Home Addition Contractor in Monrovia page.
Room Addition Contractor in Monrovia
A room addition is a smaller job, usually one new bedroom, a family room extension, or a home office added off the back or side of the house. On Monrovia’s narrower lots, we pay close attention to side-yard setbacks and window placement, since a badly placed window can trigger privacy-review delays. We scope the job, name the price, and keep the work area clean throughout. Visit our Room Addition Contractor in Monrovia page for full details.
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 Monrovia
We build with and service ADUs from Abodu, Cover, and Dvele, and we commonly specify James Hardie cladding on additions where the exterior needs to match the main house. We coordinate with the manufacturers directly on parts and panel lead times. Check our brands page for the full list of partners.
Pricing for ADU Company in Monrovia, CA
These are the ranges Monrovia homeowners should expect before they tap call. Every project gets a written line-item quote, so the final number never drifts from what we agree to.
| Service | Typical range in Monrovia |
|---|---|
| Detached ADU (full build, prefab) | $185,000 – $320,000 |
| Detached ADU (full build, site-built) | $220,000 – $380,000 |
| Attached ADU / JADU conversion | $95,000 – $180,000 |
| Garage conversion to ADU | $85,000 – $145,000 |
| Home addition (ground-up, 400 – 800 sq ft) | $160,000 – $310,000 |
| Room addition (single room, 200 – 400 sq ft) | $70,000 – $130,000 |
| Foundation work (upgrade or new) | $8,000 – $25,000 |
| Electrical panel upgrade (100A to 200A) | $3,500 – $6,500 |
| Permit and plan set fees | $4,000 – $12,000 |
What pushes a Monrovia project toward the high end of those ranges: sloped lots, difficult access for equipment, and older homes that need panel, plumbing, or seismic upgrades before construction starts. Benson ADU Builders gives every homeowner a written price before work begins, with no change orders unless the scope changes by your choice and in writing.
Neighborhoods We Serve in Monrovia
We work across the full city, from the historic districts north of Foothill Boulevard to the newer subdivisions south of the 210. Here are a few of the Monrovia neighborhoods we know well:
- North Monrovia (foothill lots with grade changes)
- Historic Old Town adjacent districts
- The area around Monrovia High School
- Southeast Monrovia near the Duarte border
- Central Monrovia south of Foothill
Response times for estimates across the Monrovia area typically run within a few business days, coordinated through our Los Angeles office, which dispatches crews serving Monrovia locally.
Service Area – Cities Near Monrovia
Beyond Monrovia, we take on ADU and addition work in nearby San Gabriel Valley communities where the housing stock and lot patterns are similar. That includes Arcadia, CA, Duarte, CA, Sierra Madre, CA, and Baldwin Park, CA. If you are just outside Monrovia, give us a call and we will confirm coverage for your street.
Serving Monrovia, CA - Our Local Coverage Area
We’re based in the Monrovia 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 Monrovia
We typically schedule the initial site visit within a few business days, and from there the timeline rests on design approvals and city plan check. Monrovia’s plan check process moves at its own pace, so we focus on getting the submittal right the first time to avoid resubmittal delays. Call (903) 568-7222 to get on the schedule.
We pull all building permits for Monrovia projects and manage the plan check comments directly. HOA approval is the homeowner’s step, though we provide the drawings and specs your association will ask for. Either way, the permit and plan set fees are named in your written price before we start.
No, not unless the scope changes and we both sign off on the change in writing. Our written price covers the work as scoped, and our 365-Day Done Right Promise covers the build for a full year after completion. Estimates are free, so call (903) 568-7222 for an exact quote on your Monrovia property.
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 Monrovia Customers Say
"Booked a consult online and met the project manager two days later. Weekly progress updates arrived by text with photos. ADU finished on schedule."
- Hannah W."Clean, quiet crew. They respected the neighbors, kept noise to working hours, and swept the driveway every evening."
- Hope C."Communication was the best part. I always knew what was happening that week without having to ask."
- Dolly N.
