General Contractor in the San Gabriel Valley

Green Design and Build is a licensed residential general contractor (CSLB #1110975) based at 16120 Sherman Way in Van Nuys. This page covers the three San Gabriel Valley cities we have written full guides for: Pasadena against the foothills, Montebello at the valley’s southwestern edge, and Diamond Bar in its southeastern corner. Each issues its own permits, and each has a site condition that decides the design.

Pasadena is about 35 minutes from our office by the 134 and 210. Montebello is about 25 miles from Van Nuys and Diamond Bar about 40 miles; for the far San Gabriel Valley it is closer to an hour each way in traffic, so we plan those projects with full-day crews and staged materials. There is no travel premium.

Each city issues its own permits

None of the three is LADBS; Altadena, across the Pasadena line, is Los Angeles County.

• Pasadena: the Permit Center at 175 North Garfield Avenue, with online submittal through the Citizen Self Service portal.
• Montebello: Building and Safety at City Hall, 1600 W. Beverly Boulevard, on a four-day week with no Friday inspections.
• Diamond Bar: Building and Safety at 21810 Copley Drive, where a Planning Inquiry Form is cleared first, and no Friday inspections.

The site conditions that decide the design

Pasadena has the most protected housing stock of any city we work in: more than twenty landmark districts, where any change to an exterior feature other than painting needs a Certificate of Appropriateness before a building permit is issued, and a Hillside Overlay over the streets against the San Gabriel foothills.

Montebello is built on an oil field. As of 2018 the Montebello Oil Field had 832 wells, 604 of them abandoned, and under CalGEM’s Construction Site Plan Review Program the local permitting agency identifies and reviews wells near or beneath proposed structures before issuing a building or grading permit.

Diamond Bar is a hillside city: hillside submittals carry an average-slope calculation and cut-and-fill mapping, and any grading application needs a complete soils and geology report. Much of The Country Estates and most of the open space sit in a Very High Fire Hazard Severity Zone, where Los Angeles County Fire requires an approved fuel modification plan for new structures and for additions of 50 percent or more.

San Gabriel Valley housing stock

Pasadena holds the largest concentration of Craftsman homes in Southern California, from the 1900s to 1920s. Montebello is a 1940s-to-1970s city: just over 80 percent of its homes were built between 1940 and 1979. Diamond Bar is a planned community whose first model homes went up in 1960, with about half of its housing built before 1980. Whatever the era, expect original panels, dated plumbing and lead-based paint before 1978.

Utilities differ too: Pasadena Water and Power handles electrical service changes in Pasadena, SCE serves Montebello and Diamond Bar, and Montebello has four water providers rather than one.

ADUs in the San Gabriel Valley

State ADU law sets a floor that every city has to meet, and our ADU rules calculator shows what that floor is for your lot. Pasadena allows a detached ADU of up to 1,200 square feet outside its overlays, and every Pasadena rule is laid out in our Pasadena ADU rules guide and our Pasadena ADU page.

In Montebello, the state Department of Housing and Community Development wrote to the city in October 2025 noting that its ADU ordinance on file dates from 2019 and may be out of compliance with state law; where a local handout conflicts with state law, state law controls. Diamond Bar allows ADUs up to 850 square feet for studios and one bedroom and 1,000 for two or more. Our ADU page and garage conversion page cover the rest.

What we build most here

• Kitchen remodeling: Craftsman kitchens rebuilt behind an unchanged facade in Pasadena, mid-century plans opened up elsewhere; see kitchen remodeling in Pasadena.
• Room additions: the most common request in Montebello, and in Diamond Bar sized against the 50 percent fire-zone threshold.
• Bathroom remodeling, including full layout changes and multi-bathroom projects.
• Whole-home renovations of century-old Pasadena houses and 1940s Montebello stucco homes.
• Foundation and structural work: bolting and cripple-wall bracing, hillside retaining walls, seismic upgrades.
• ADUs and garage conversions under the rules above.

On our published Los Angeles budgeting ranges, a kitchen remodel here runs $25,000–$100,000+, a bathroom $8,000–$80,000+ and a ground-floor room addition $300–$500 per sq ft, with an addition taking nine to fourteen months end to end; see what remodeling costs in Los Angeles.

City guides

• General contractor in Pasadena, plus two kitchens, one with a load-bearing wall removed and one rebuilt with an island.
• General contractor in Montebello: the four-day week and well review.
• General contractor in Diamond Bar, plus two full bathrooms and a three-quarter bath finished in 2026.
• Neighboring Glendale and Burbank run their own building departments too; see also our Los Angeles County page and the full list of areas we serve.

If you lost a house in the January 2025 Eaton Fire, in Upper Hastings Ranch or Altadena, the rebuild runs on different rules; see our fire rebuild page.

Plan your San Gabriel Valley project

Tell us the street and what you want to build, and we will schedule a free site visit and give you a written, itemized estimate.

These are each city’s own rules and can change; confirm what applies to your address with the department before you plan around a date.