Lic #1007864 · San Mateo County · General Contracting
Custom ADU & Additions
Detached ADUs, room additions, garage conversions, and JADUs — permitted, engineered, and built to estate standards.
Celebrity-mansion territory — full-scale estate remodels, structural transformations, and grounds construction executed with total discretion.
California's ADU laws have unlocked enormous property value, and JMG builds accessory dwelling units and home additions that match the main residence — not prefab afterthoughts. From Los Altos to San Ramon, our ADUs and additions command premium rents and appraisals.
In Hillsborough and across San Mateo County, JMG delivers adus & additions under California Contractor's License #1007864 — permitted, inspected, and personally overseen by owner Jerry Guinn. We manage the entire lifecycle: feasibility, design, permitting, utilities, and construction, delivering turnkey units and seamless additions ready for family or income.
Hillsborough requires design review through the Town's Building & Planning Department, and its hillside estates bring slope, drainage, and retaining-wall engineering into nearly every project. From Hillsborough Oaks to the Carolands area, we coordinate geotechnical reports, view-sensitive design, and the town's exacting inspection standards.
What's included in Hillsborough
Recent adus & additions work
The process in Hillsborough
Private Consultation
Walk the property with owner Jerry Guinn. Honest scope, realistic timeline, and a written line-item estimate — free.
Design & 3D Rendering
See the finished project in photorealistic 3D before a single wall comes down. Finishes get locked before demo day.
Permits, Handled
Plans, submittals, corrections, and city or county coordination under CA License #1007864. You sign — we run the process.
Build & Final Inspection
Sixteen in-house trades on one schedule, one accountable owner. Inspection passed, walkthrough done, keys in hand.
ADUs & Additions in Hillsborough — FAQ
Feasibility check on your lot, design and 3D rendering, permit submittal, then construction. State law guarantees most ADUs a 60-day ministerial review — we prepare complete packages so that clock never stops.
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ADUs & Additions · Hillsborough