Adding On In Farm Hill: Hillside Setbacks Explained

Planning to add a bedroom, expand your kitchen, or pop up a second story in Farm Hill? On hillside lots, the rules can feel tricky and the review process can surprise you. You want a clear path that protects your budget and timeline while keeping the neighborhood’s character intact. In this guide, you’ll learn how Redwood City’s RH hillside standards, step-backs, pervious area rules, and stormwater requirements shape your design. Let’s dive in.

RH hillside zoning, in plain English

Redwood City uses the RH designation to guide development on steeper lots. The goal is to limit grading, protect views and trees, and keep slopes stable. That means your addition must fit inside a building envelope with specific setbacks and height controls.

Expect overlapping reviews. Planning and zoning oversee design and setbacks, while Public Works focuses on stormwater and grading. Some projects also need geotechnical input for slope stability. If your property is in an unincorporated pocket, confirm whether San Mateo County rules apply.

Setbacks and building envelopes

Setbacks define how close you can build to property lines and steep areas. In hillside neighborhoods, these distances can be larger or variable to account for slope and views. You may also see additional setbacks from features like ridgelines or banks.

Pushing too close to property lines or up the slope can trigger discretionary review. If your concept encroaches into a required setback, you may be looking at a variance. That adds time, uncertainty, and redesign risk, so plan your envelope early.

Practical design moves for setbacks

• Start with a current topographic survey and tree inventory to map a realistic envelope.
• Keep new walls inside the existing footprint where possible to avoid variance requests.
• Use split-level layouts to fit the slope without heavy grading.

Second-story step-backs

Upper-floor step-backs are common in hillside zones to reduce perceived mass and protect privacy and view corridors. A step-back means the second story sits further in from the edges of the first story or property line.

This control affects how you add space vertically. It can limit a full two-story box over an expanded footprint. Designs that tuck the upper level into the slope or that favor modest horizontal additions often sail through review more smoothly.

Massing tips that work on hillsides

• Set the second floor back from street and downhill elevations to soften height.
• Break up long wall planes with offsets or material changes for lighter visual mass.
• Consider a partial pop-up or a split-level instead of a full second story.

Pervious area and drainage

Hillside properties must manage runoff carefully. Cities use pervious area requirements or impervious coverage limits to keep infiltration on site and protect downstream channels. When you add roofs or hardscape, you may need on-site stormwater features.

If your addition expands driveways, patios, or roof area, be ready to show how you maintain required pervious area. Simple swaps like permeable paving or a small rain garden can keep you under thresholds and simplify approvals.

Common stormwater solutions

• Rain gardens or bioretention to capture roof and patio runoff near the source.
• Permeable pavers for driveways, walkways, and courtyards with a properly engineered base.
• Downspout disconnection to pervious areas or cisterns for irrigation reuse.
• When infiltration is limited, detention tanks or oversized cisterns with controlled release.

Geotechnical and grading

On slopes, soil behavior drives safe design. Many exterior additions, retaining walls, or grading activities require a geotechnical report. Your engineer may recommend specific foundation systems, limits on cut and fill, and drainage details behind retaining walls.

Plan for erosion control during construction. Protecting existing drainage patterns and stabilizing disturbed soil helps prevent sediment from moving downhill. Good temporary controls also reduce inspection delays.

Geotech and grading best practices

• Scope geotechnical work early to avoid redesigns during plan check.
• Preserve natural drainage paths and avoid concentrating flows down the slope.
• Add behind-the-wall drainage and weep systems for any retaining structures.

Trees and landscape protection

Trees stabilize slopes and contribute to hillside character. Redwood City regulates removal of protected or heritage trees and requires protection of root zones during construction. Tree issues can affect your layout and schedule.

Work with an arborist if a significant tree sits near your addition. In many cases, modest footprint shifts or pier-and-grade-beam foundations can save a tree and keep your project moving.

Smart site planning for Farm Hill

Small early choices can cut costs and reduce triggers. Start with clear base data, then design within the hillside context. You will often save time by choosing materials and layouts that maintain pervious area and minimize grading.

Focus on solutions that manage water where it falls. Harvest and infiltrate first, then detain if needed. This approach aligns with local stormwater intent and typically simplifies Public Works review.

Design moves that reduce friction

• Favor horizontal expansions over full two-story stacks where step-backs apply.
• Use permeable materials for new hardscape to preserve pervious percentages.
• Capture roof runoff in rain gardens or cisterns to lower runoff volume and support drought-tolerant landscaping.
• Step foundations to the terrain to reduce cut-and-fill and wall height.

Permitting steps and timing

Most projects follow a predictable path. Start with a planning conversation, then submit a complete package. Expect separate reviews by planning, public works, and building.

Simple, code-compliant additions can move through in several months, depending on submittal quality and staff workload. If you need design review, variances, geotechnical studies, or engineered stormwater controls, plan for a longer timeline that can extend to several months or more.

Typical submittal package

• Zoning compliance checklist and site plan with existing and proposed pervious and impervious areas.
• Stormwater control plan or drainage memo with BMP sizing and discharge points.
• Grading and erosion control plan for the construction period.
• Geotechnical report if grading, retaining walls, or slope work are involved.
• Tree report if protected trees are present.

Neighbor outreach and visuals

Visible hillside work often raises questions. Early outreach can reduce friction during review. Clear drawings and simple 3D massing studies help neighbors understand how height and step-backs reduce bulk.

If a variance or design review is needed, add time for public notice and potential hearings. Proactive communication can prevent surprises later.

Quick homeowner checklist

• Confirm your parcel zoning and any hillside overlays.
• Order a topo survey and tree inventory before schematic design.
• Budget for a geotechnical report if you touch slopes, grade, or add retaining walls.
• Calculate current and proposed impervious area and explore permeable options early.
• Draft a stormwater concept that favors infiltration or harvest near downspouts.
• Schedule a pre-application conversation with planning and public works.
• Prepare neighbor-friendly visuals if your addition affects downhill views.

Your next step

With the right plan, a Farm Hill addition can add space and value while respecting the hillside. Start with data, design to the slope, and choose stormwater solutions that work with the site. This approach reduces review risk and keeps your project moving.

If you want a local, practical game plan for your property and referrals to designers, engineers, and contractors who understand hillside rules, reach out to Unknown Company. Get your free home valuation and a tailored next-step checklist.

FAQs

What is RH hillside zoning in Redwood City?

• RH zoning sets standards for hillside lots to limit grading, protect views and trees, and maintain slope stability through setbacks, height controls, and design review.

How do second-story step-backs affect Farm Hill additions?

• Step-backs require upper floors to sit in from edges to reduce bulk and protect privacy, which can limit full two-story boxes and favor split-level or tucked designs.

What counts as pervious area on a hillside lot?

• Pervious area includes landscaping and materials that let water soak in, such as planted areas or permeable paving, which help meet runoff and water-quality goals.

When do I need a geotechnical report in Farm Hill?

• Many exterior additions that involve grading, retaining walls, or work on steeper terrain trigger geotechnical review to confirm safe foundations and drainage.

How long does permitting take for a Farm Hill addition?

• Code-compliant projects can take several months. If design review, variances, geotechnical studies, or stormwater engineering are required, expect a longer timeline.