Home Additions in Gilroy, CA
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The 3,600 sq ft Sprinkler Line
Fire sprinklers in Gilroy are required for full rebuilds, and for additions of 500 sq ft or more that bring the building to 3,600 sq ft or more.
That means a 500 sq ft addition to a 3,100 sq ft home triggers sprinklers, while the same addition to a 2,500 sq ft home does not. We run the numbers before design so the decision is yours.
Addition Work
Historic Homes, Trees and Hillsides
- Historic resources: Gilroy’s historic preservation rules are in Municipal Code §30.27, with documented historic homes on Alexander, Church and Monterey Streets and others. Mills Act contracts, which can reduce property taxes for qualifying historic homes, are available, with applications taken each July.
- Trees: a permit and an ISA arborist report are needed for protected native trees, including oaks, bay, madrone, sycamore and buckeye, with a trunk 38 inches or more in circumference at 4½ feet, and for heritage trees of any species at 90 inches or more. Orchards and fruit trees are exempt.
- Hillside and wildfire areas: Gilroy adopted CAL FIRE fire hazard severity zones in June 2025, and Class A roofs are required in wildland-urban interface areas and for all hillside construction.
Design review requirements for larger additions and historic properties are set by Planning; we confirm the review path for your lot early.
Permits
7351 Rosanna Street, Gilroy, CA 95020
Building (408) 846-0451 · Planning (408) 846-0440, Pl**************@**********oy.org
Counter Monday to Thursday, 8:30 a.m. to 4:30 p.m. Applications go through the GO Permit (Gilroy Online Permit) Portal. Plans must be digital, submitted as one bookmarked PDF; paper sets are not accepted.
Inspections are booked in the GO Permit Portal, and the City notes appointments are scheduled about 72 hours out. Inspections are required before concealed work is covered, permits expire after 365 days without an inspection, and a final inspection is required. Contractors need a City of Gilroy business license as well as a state license.
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Other Gilroy services: ADUs · Bathrooms · Kitchens · New Homes · Gilroy overview
Same service nearby: Morgan Hill · San Martin
See home additions and second stories.
Gilroy Home Additions FAQ
When does an addition require sprinklers in Gilroy?
When an addition of 500 sq ft or more brings the building to 3,600 sq ft or more, or for a full rebuild.
Can I get a Mills Act contract?
Mills Act contracts are available for qualifying historic properties, with applications each July.
Are oak trees protected in Gilroy?
Native trees 38 inches or more in circumference need a permit and an arborist report.
What roofing is required on hillsides?
Class A roofing, required for all hillside construction and in wildland-urban interface areas.