Adding On Without Losing What Makes a Kentfield Home Special
Kentfield sits at the base of Mt. Tamalpais in the Ross Valley, and the homes here carry that setting in their bones. Up in Kent Woodlands you have hillside estates, Spanish Revival and Mediterranean villas, shaded midcentury models, and Craftsman houses on large, wooded parcels. Down in the Kentfield Gardens flats near College of Marin, you have walkable family homes with their own scale and rhythm. A home addition here is never a generic box on the back of a house. It has to read as if it was always part of the home and hold up to the light that moves across the valley all day.
New Key Construction is a Marin design-build firm, which means interior design and construction live under one roof. When you add a primary suite, expand a kitchen into a family wing, or build out a lower level on a downslope lot, you work with one team from the first sketch through the final coat of paint. There is no handoff between an architect who drew it and a contractor who has never seen the intent. The people who design your addition are accountable for building it.
One Team, Priced Options, And Renderings Before Permits
Most addition projects go sideways in the gap between design and construction. A beautiful set of plans comes back over budget, and the redesign starts from scratch. We close that gap by pricing options up front. Before you commit, you see real numbers tied to real choices, so you can decide between a modest bump-out and a full wing knowing what each one actually costs.
Before any permit is pulled with Marin County, we build photoreal 3D renderings of your addition. You walk through the new space on screen and see how the new roofline meets the existing one and how the materials read against your home's original character. On Kentfield's hillside lots and tree-covered parcels, a roof or a window placement is often the difference between an approval and a redesign, so seeing the project before it is built protects the budget and the timeline.
Throughout, you get white-glove project management: one point of contact, a clear schedule, and a team that keeps the jobsite respectful of a quiet residential street. We coordinate the structural engineering, the surveys, and the trades so you are not chasing vendors.
Built For Marin County's Permit And Design Review Reality
Kentfield is unincorporated, so your addition is reviewed by the Marin County Community Development Agency, not a city hall. Additions here typically trigger Design Review, and when the existing house is under 4,000 square feet that often means a Major Design Review, a planning process that commonly runs around three months before you reach a building permit. As of January 2026, the County no longer accepts paper plans, so every submittal moves electronically through the County portal, beginning with the Part A application and checklist.
We design with those rules in front of us, not behind us. That means watching grading and downslope structure on Kent Woodlands hillsides, respecting setbacks and the wooded character of large parcels, and accounting for creek and drainage conditions in the flats. If your property falls under the Kent Woodlands Property Owners Association, we factor that architectural review into the schedule alongside the County so the two processes move together. For complicated scopes, the County offers a voluntary pre-submittal review, which we use to surface problems early instead of mid-construction.
The payoff of doing the homework is a calmer build: fewer surprises at plan check, fewer revisions, and an addition that holds its value because it was designed for this jurisdiction from day one.
Frequently Asked Questions
Do I need design review for a home addition in Kentfield?
Most likely, yes. Because Kentfield is unincorporated, additions are reviewed by the Marin County Community Development Agency, and additions to homes commonly require Design Review. If the existing house is under 4,000 square feet, that often means a Major Design Review. We prepare the plan set and renderings specifically to move that review along.
How long does the permit process take?
Plan on the planning side first. A Major Design Review commonly runs around three months, and the building permit review that follows typically takes several weeks because of the coordination involved. We design to County standards up front and submit complete electronic plan sets through the portal to avoid the back-and-forth that stretches timelines.
Does the Kent Woodlands HOA review additions?
If your property is within the Kent Woodlands Property Owners Association, your addition will generally go through its architectural review in addition to the County process. We build that into the schedule so both reviews advance in parallel, and our 3D renderings give both the County and the association a clear, accurate picture of the proposed work.
What does a home addition in Kentfield cost?
It depends on scope, site conditions, and finish level, and Kentfield's hillside and wooded lots can add structural and grading work that a flat lot would not. Rather than quote a number we cannot stand behind, we price options up front, so before you commit you can decide between a smaller bump-out and a full wing with real numbers in hand.
Can you handle both the design and the construction?
Yes. We are a design-build firm, so one team handles design and construction together. You are not managing an architect and a separate contractor who never spoke to each other. The people who design your addition are the ones accountable for building it.
If you are weighing an addition in Kentfield or Kent Woodlands, let's start with a conversation and a clear look at your options. We will show you priced choices and a photoreal 3D rendering of your new space before a single permit is pulled. Reach out to New Key Construction to begin.
