Remodeling and additions in Redwood City, San Carlos & Belmont

Building on a slope

Hillside lots in Emerald Hills, Farm Hill and the hills above San Carlos and Belmont come with views and privacy, and with a slope that drives the design. Each city has its own rules, and Emerald Hills is unincorporated, so it is reviewed by San Mateo County rather than a city.

What the reviews look at. In Redwood City, larger projects on sloping lots, and changes of any size on the steepest lots, need an Architectural Permit; the findings ask that a design respect the site's natural constraints, avoid excessive grading, and minimize large exterior walls, upper-story massing and exposed underfloors. San Carlos applies a Hillside Overlay to steeper lots, with height measured from the lowest finished grade, step-backs on downhill walls, cut and fill balanced on site, part of the lot left natural, and stepped foundations as the standard approach. Belmont reviews new homes and larger upper-floor additions through single-family design review, and doesn't allow grading during the winter rain period without an exception.

Grading and soils. All three cities require a grading permit once excavation or fill goes beyond a small amount (around 50 cubic yards, or a cut or fill more than a few feet deep), and hillside projects usually need a soils or geotechnical report before permits are issued. The exact triggers depend on the city and the project. That report sets the foundation design, so it comes first.

Foundations, access and cost. Hillside houses are usually built on stepped foundations, drilled piers with grade beams, or retaining walls rather than a simple slab. Access is often the hidden cost: narrow streets, steep driveways and little room to stage materials can mean smaller equipment, pumped concrete and more labor hours. Those items make a hillside project cost more than the same square footage on a flat lot, so we price them line by line after the soils report instead of carrying a vague allowance.

Our part: we arrange the survey and soils investigation, prepare drawings, coordinate structural and geotechnical engineering, prepare the planning and grading submittals, respond to comments, and schedule the work and inspections around the grading season where it applies.

Last reviewed: October 2026 · Sources: Redwood City Zoning Code — Article 45, Architectural Permits (opens in new tab) · Redwood City Code — Chapter 9, grading (Appendix J amendments) (opens in new tab) · City of Redwood City — Residential building permit checklist (opens in new tab) · San Carlos Municipal Code — Chapter 18.12 Hillside Overlay District (opens in new tab) · San Carlos Municipal Code — Chapter 12.08 Grading (opens in new tab) · Belmont City Code — Chapter 9 Grading (opens in new tab) · City of Belmont — Grading permit guidelines (opens in new tab) · City of Belmont — Hillside development (opens in new tab) · San Mateo County — Emerald Lake Hills Design Review Officer (opens in new tab)