The best additions are indistinguishable from the original architecture. We engineer structural expansions that preserve your home's integrity — adding primary suite wings, expanded living spaces, and second stories that frame Marin's hillside views. Every new square foot is designed to feel as if it has always been there.
Home additions require a level of structural and aesthetic coordination that separates expert general contractors from production builders. We manage structural engineering, material matching, roofline integration, and permit approval as a single unified scope — ensuring that your addition enhances rather than compromises your property's value and architectural character.
ConstruBay (CSLB #1106798) is based in Mill Valley and has executed home addition projects across Marin, Sonoma, and Napa Counties.
What Is Included
The Marin Advantage
Home additions in Marin County are subject to some of the most rigorous setback, height, and FAR (floor area ratio) restrictions in California — particularly in cities like Mill Valley, Tiburon, and Belvedere. Our PlanPass.ai permit intelligence platform pre-screens addition projects for zoning compliance before we invest in construction drawings, identifying potential variances or Design Review Board requirements early. We have completed primary suite wings, garage additions, and second-story expansions throughout Marin County, navigating hillside setback requirements, view corridor protections, and neighbor notification processes as part of our standard project management.
Our Process
Curation & Design
We begin with an in-depth discovery session at your property, translating your vision into a fixed-scope brief with transparent pricing.
Artful Execution
Our licensed craftsmen execute with precision under direct site supervision — every material sourced, every detail approved by you before installation.
The Final Reveal
A thorough walkthrough with your project lead ensures every element meets our standard before you take possession of your transformed space.
Investment Range
$150,000 – $400,000+
Typical Project Range
All projects are delivered under a fixed-scope contract — the number you approve is the number you pay.
Frequently Asked Questions
Begin Your Project
Begin Your Home Addition Project
Fixed-scope contract. No surprises. Schedule a private consultation with Paulo.