# ADU Builder & Home Additions in Monrovia, CA [Browser-friendly HTML version](https://www.remodelyourvibe.com/website-guide/pages/services/adus-additions/monrovia/index) Source: https://www.remodelyourvibe.com/services/adus-additions/monrovia Last modified: 2026-09-24T00:00:00.000Z Text part: 1 of 1 [Full website text index](https://www.remodelyourvibe.com/llms-full.txt) | [Services by city](https://www.remodelyourvibe.com/llms/services-by-city-005.txt) | [Previous page](https://www.remodelyourvibe.com/llms/pages/services/adus-additions/la-crescenta-montrose/index.txt) | [Next page](https://www.remodelyourvibe.com/llms/pages/services/adus-additions/temple-city/index.txt) --- Image: Open-plan living room and kitchen with polished concrete floors 1. [Home](https://www.remodelyourvibe.com/) 1. [Services](https://www.remodelyourvibe.com/services) 1. [ADUs & Additions](https://www.remodelyourvibe.com/services/adus-additions) 1. Monrovia Design · Permit · Build ### ADUs & Additions in Monrovia Detached ADUs, garage conversions and additions, from plans to move-in. [Book a Consultation](https://www.remodelyourvibe.com/contact-us) [Call 818-300-2393](tel:+18183002393) #### Built for Monrovia Homes Monrovia is the fourth oldest city in Los Angeles County, and it has held on to a large share of its historic housing stock, with historic districts at Wild Rose Tract and North Encinitas. The city sits at the foot of the San Gabriel Mountains, and in 2016 it opened more than four and a half miles of trails in its Hillside Wilderness Preserve, looking out over Monrovia and the San Gabriel Valley. A backyard project here often answers to one of those two settings. On a landmark or a contributing district home, the Historic Preservation Commission reviews alterations, from new structures to grading and tree removal; on a foothill lot, grading thresholds, pad-edge setbacks, protected oaks and defensible space settle the footprint before design begins. Minimum lot size follows the zone: 7,500 square feet in Residential Low-Density, 20,000 in Residential Estate, and 15,000 in Residential Foothill, where lots in a development must also average more than an acre. On every residential lot a pool stays out of the front yard and at least five feet from the side and rear property lines. We are a design-build team, which means the people who draw your project are the people who build it. Design, engineering, permits and construction run through one project manager and our own crews, so nothing gets lost in a handoff between a salesperson and a subcontractor. We are licensed, bonded and insured, [CSLB license #1119054](https://www.cslb.ca.gov/OnlineServices/CheckLicenseII/LicenseDetail.aspx?LicNum=1119054) . Permits in Monrovia: Building permits, plan check and inspections run through the Building Division of the Community Development Department. In the Residential Foothill, Residential Estate and Residential Low-Density zones, a Hillside Development Permit is also required for a new house, or for earth movement with a footprint over 500 square feet, whenever the work involves five feet or more of cut or fill or a retaining wall six feet or taller, with swimming pools and basements excluded. New homes and two-story additions that are not already under a Hillside Development Permit go through neighborhood compatibility design review before the Development Review Committee, while single-story second units and single-story accessory structures in side or rear yards are exempt. Alterations to a designated landmark or a contributing property in the Wild Rose Tract or North Encinitas historic districts need a Certificate of Appropriateness from the Historic Preservation Commission, which must hold its public meeting no later than 50 days after a completed application is received. Permit details checked September 2026 against [Monrovia Municipal Code](https://codelibrary.amlegal.com/codes/monrovia/latest/monrovia_ca/0-0-0-71795) and [City of Monrovia](https://www.monroviaca.gov/discover-monrovia/historic-preservation) . Rules change, so we confirm them again for your parcel. What We Build - Hillside Development Permit grading plans - Certificate of Appropriateness submittals - Pad-edge setback and retaining wall layout - Oak tree preservation permits - Fire-zone rated exterior walls and glazing - Detached ADUs, ground-up - Garage conversions to living space - Junior ADUs within the main house - Room additions and bump-outs - Second-story additions - Full kitchens and bathrooms in the ADU - Separate utility metering where required - Private entries, patios and landscaping - Plans, engineering and city submittals - Title 24 energy compliance Local Conditions #### What to Know in Monrovia These local conditions change the scope, the schedule and the budget. 01 In the Residential Foothill zone, where a pad sits beside a slope of three feet or more, structures must be set back from the side and rear pad edge by one third of the slope height, up to 15 feet for the single-story portion, and a second story sits a full 15 feet back. A retaining wall that extends the pad is limited to three feet unless a house, garage or other permitted structure screens it from the street and neighboring parcels. 02 New construction and additions in the Very High Fire Hazard Severity Zone fall under a local Building Code chapter that requires one-hour fire-resistive exterior walls with double-glazed exterior glass, though a one-story detached accessory building with no more than 484 square feet of projected roof area, set at least 20 feet from the primary building, is excepted. 03 The city's vegetation fire hazard ordinance keeps the 30 feet around any structure free of natural vegetation such as sumac, buckwheat and sage, holds highly flammable ornamentals such as eucalyptus, pine, cypress and juniper at least ten feet from buildings, and in the Very High Fire Hazard Severity Zone extends defensible space to 200 feet, which shapes planting around pools, decks and outdoor rooms. 04 Oaks ten inches or more in diameter, measured two feet above ground, in a single-family front yard or street-facing side yard, and every oak on a vacant lot, need an oak tree preservation permit from the Development Review Committee before removal, pruning of more than a third of the crown, foliage or roots, or any grading or irrigation inside the drip line. Areas we serve in Monrovia:Old TownWild Rose TractNorth Encinitas Investment #### What It Costs in Monrovia Real Southern California price ranges, not teaser numbers. ##### Detached ADU $150,000 to $400,000+ What moves it: square footage, finish level, utility runs, and site access; garage conversions typically run well below a ground-up detached build ##### Garage conversion ADU $80,000 to $180,000 What moves it: whether the existing slab and framing meet current code, how far utilities have to run, and the finish level of the kitchen and bathroom ##### Plans, drawings and permit management $4,500 to $25,000+ What moves it: project type and size, whether structural engineering, Title 24 or a soils report is required, and how many jurisdictions or review bodies are involved Your lot, access and finishes set the price. We walk the site, then show you where every dollar goes. [Get a line-item price for your Monrovia property](https://www.remodelyourvibe.com/contact-us) The Process #### How We Work in Monrovia 01 ##### Feasibility We check lot size, setbacks, utilities and access to confirm what your property will actually support. 02 ##### Design & 3D Layout, elevations and finishes, modeled in 3D so you approve the unit before submittal. 03 ##### Plans & Permits We prepare the full drawing set, handle engineering and Title 24, and manage the city submittal and corrections. In Monrovia that submittal goes to City of Monrovia Community Development Department, Building Division. 04 ##### Foundation & Framing Site prep, foundation, framing and dry-in by our own crews. 05 ##### Systems & Finishes Electrical, plumbing, HVAC, insulation, then kitchen, bath and interior finishes. 06 ##### Final Inspection We pass final inspection, walk the unit with you and hand over the keys. Questions #### What Monrovia Homeowners Ask Who issues the permits for this work in Monrovia? City of Monrovia Community Development Department, Building Division. Building permits, plan check and inspections run through the Building Division of the Community Development Department. In the Residential Foothill, Residential Estate and Residential Low-Density zones, a Hillside Development Permit is also required for a new house, or for earth movement with a footprint over 500 square feet, whenever the work involves five feet or more of cut or fill or a retaining wall six feet or taller, with swimming pools and basements excluded. New homes and two-story additions that are not already under a Hillside Development Permit go through neighborhood compatibility design review before the Development Review Committee, while single-story second units and single-story accessory structures in side or rear yards are exempt. Alterations to a designated landmark or a contributing property in the Wild Rose Tract or North Encinitas historic districts need a Certificate of Appropriateness from the Historic Preservation Commission, which must hold its public meeting no later than 50 days after a completed application is received. We prepare the drawings, make the submittal and handle plan-check corrections ourselves, so you are not the one chasing plan check. What makes building in Monrovia different? Minimum lot size follows the zone: 7,500 square feet in Residential Low-Density, 20,000 in Residential Estate, and 15,000 in Residential Foothill, where lots in a development must also average more than an acre. On every residential lot a pool stays out of the front yard and at least five feet from the side and rear property lines. One local condition that shapes the work: In the Residential Foothill zone, where a pad sits beside a slope of three feet or more, structures must be set back from the side and rear pad edge by one third of the slope height, up to 15 feet for the single-story portion, and a second story sits a full 15 feet back. A retaining wall that extends the pad is limited to three feet unless a house, garage or other permitted structure screens it from the street and neighboring parcels. Which parts of Monrovia do you work in? All of it, including Old Town, Wild Rose Tract and North Encinitas. Our crews run every job out of our Cahuenga Pass base in Los Angeles, with our own people on site. What does an ADU or addition cost in Monrovia? Detached ADU: generally $150,000 to $400,000+ across Southern California. What moves it is square footage, finish level, utility runs, and site access; garage conversions typically run well below a ground-up detached build. We give line-item pricing after seeing the site rather than quoting a number over the phone. How long does an ADU take start to finish? Plan a realistic year. Design and engineering typically take one to three months, city plan check and corrections add several more, and construction usually runs four to eight months depending on size and site access. Is a garage conversion cheaper than a detached ADU? Usually yes, and often substantially, because the foundation, walls and roof already exist. The trade-offs are that you lose the garage, and older slabs and framing sometimes need upgrading to meet current code. Can I rent the ADU out? California ADU law is designed to allow long-term rental, and an ADU is one of the few ways to add rentable square footage to a single-family lot. Short-term rental rules vary by city, so confirm your local ordinance before counting on that income. Do you handle the permits? Yes. Plans, engineering, Title 24 and the city submittal are all handled in-house, including responding to plan-check corrections. That is a service we sell on its own, so it is not something we hand off. #### More Services in Monrovia [Pool & Spa Remodeling in Monrovia](https://www.remodelyourvibe.com/services/swimming-pool-spa/monrovia) [Backyard & Outdoor Living in Monrovia](https://www.remodelyourvibe.com/services/exterior-remodeling/monrovia) [Everything we build in Monrovia](https://www.remodelyourvibe.com/service-areas/monrovia) #### ADUs & Additions Nearby [ADUs & Additions in Arcadia](https://www.remodelyourvibe.com/services/adus-additions/arcadia) [ADUs & Additions in Sierra Madre](https://www.remodelyourvibe.com/services/adus-additions/sierra-madre) [ADUs & Additions in Pasadena](https://www.remodelyourvibe.com/services/adus-additions/pasadena) [ADUs & Additions in San Marino](https://www.remodelyourvibe.com/services/adus-additions/san-marino) [ADUs & Additions in Altadena](https://www.remodelyourvibe.com/services/adus-additions/altadena) Planning Guides #### Before You Build in Monrovia Costs, materials and process notes from our own projects. [ADU Cost Breakdown by Size in Los Angeles A detached ADU in Los Angeles runs $150,000 to $400,000-plus. Here is the real cost broken down by unit size, with the soft costs, utility work and finish decisions that move the number. Read guide](https://www.remodelyourvibe.com/articles/adu-cost-breakdown-by-size-los-angeles) [Garage Conversion to ADU: The Step-by-Step Build A garage conversion runs $80,000 to $180,000 in Southern California. Here is the real sequence, from slab testing and plan check to the raised floor, the mini-split and final sign-off. Read guide](https://www.remodelyourvibe.com/articles/garage-conversion-adu-step-by-step) [ADU Rental Income Math in the San Fernando Valley A one-bedroom ADU in the San Fernando Valley rents for roughly $2,100 to $2,900 a month. Here is the honest arithmetic on payback, carrying costs and what the unit adds to the property. Read guide](https://www.remodelyourvibe.com/articles/adu-rental-income-san-fernando-valley) [Second Story Addition vs Building Out: Which Costs Less Building out runs $350 to $500 per square foot. Going up runs $450 to $700. Here is when the cheaper option is actually the wrong one, and what drives each number. Read guide](https://www.remodelyourvibe.com/articles/second-story-addition-vs-building-out) #### Planning an ADU in Monrovia? Sit down with your project manager and get an accurate estimate. We call you back within one business day. [Book a Consultation](https://www.remodelyourvibe.com/contact-us) [818-300-2393](tel:+18183002393) Licensed, bonded & insured · [CSLB license #1119054](https://www.cslb.ca.gov/OnlineServices/CheckLicenseII/LicenseDetail.aspx?LicNum=1119054) --- End of text part 1 of 1. This page is complete.