Planning a remodel or a new build in Los Altos and trying to decode FAR and lot coverage? You are not alone. These two standards shape what you can build, how large it can be, and where it can sit on your lot. In this guide, you will learn what FAR and lot coverage mean, how to run quick calculations, where to confirm your exact limits, and smart strategies to design within Los Altos rules. Let’s dive in.
What FAR means
Floor Area Ratio, or FAR, compares the total floor area of your home to the size of your lot. The basic formula is simple: FAR equals total floor area divided by lot area. Cities express it as a decimal or percent, such as 0.40 or 40 percent.
What typically counts as floor area is conditioned living space above grade, which can include enclosed porches or balconies depending on local definitions. Some spaces are commonly excluded, such as certain basements, open porches, or attics below a height threshold. Because definitions vary by city, you should always confirm what Los Altos counts as floor area before you design.
Here is an illustrative example. On a 6,000 square foot lot with an assumed FAR of 0.50, the maximum floor area would be 3,000 square feet. That could be a two‑story home with 1,500 square feet per level. Whether a 400 square foot garage is included depends on local code, so verify with Los Altos Planning.
What lot coverage means
Lot coverage measures how much of your lot is covered by roofed structures at ground level. The formula is the footprint area of all buildings divided by the lot area. Cities typically express it as a percentage.
Covered patios, porches, attached garages, and accessory structures often count toward coverage, unless the code excludes them. Open, unenclosed features like landscaping usually do not count. Again, Los Altos has its own definitions, so confirm the local rules for your property.
For a quick example, if a 6,000 square foot lot has a 2,000 square foot ground‑floor footprint, lot coverage is about 33.3 percent. A second story would not change lot coverage, but it would change FAR.
Why both rules matter
FAR influences overall building size and interior space, while lot coverage shapes how much yard area remains at grade. Cities pair these with height and setback rules to manage neighborhood scale and privacy.
Even if you calculate a generous FAR, height limits, setbacks, tree protection, and design standards can limit how much you can actually build. Plan with all of these controls in mind.
Where to find Los Altos rules
Los Altos regulates FAR and lot coverage through its zoning ordinance and municipal code. The Planning Division enforces these standards and provides process guidance for new homes, additions, and ADUs.
Standards vary by residential zone, often labeled with R designations. Each zone sets minimum lot size, maximum height, maximum lot coverage, maximum floor area or FAR, and required setbacks. For parcel‑specific confirmation, request a zoning verification or speak with Los Altos Planning.
Because codes evolve, do not rely on old handouts or neighbor anecdotes. Confirm your current zone and standards directly with the City before you invest in design work.
How to calculate your numbers
Use this simple approach to frame early feasibility:
- Step 1: Find your lot area from a survey, assessor data, or parcel map.
- Step 2: Confirm the zone for your parcel and the applicable FAR or maximum floor area, plus the lot coverage limit.
- Step 3: Calculate preliminary allowable floor area using FAR times lot area. Keep a list of what your local code includes or excludes in floor area.
- Step 4: Calculate preliminary lot coverage by mapping the ground‑floor footprint of all roofed structures, then divide by lot area.
- Step 5: Cross‑check setbacks, height limits, and any tree protection constraints that may reduce what fits in practice.
- Step 6: Adjust your concept and repeat until your design fits both FAR and lot coverage, along with setbacks and height.
ADUs, garages, and basements
California ADU laws limit how cities can restrict ADUs. Many jurisdictions, including those in Santa Clara County, process ADUs ministerially and have limited ability to count them toward FAR or coverage in some situations. In Los Altos, whether an ADU counts against FAR or lot coverage depends on local code within the bounds of state law, so verify with Planning.
Garages are often counted toward lot coverage because they add footprint. Whether a garage counts toward FAR varies by local definition. If you are close to your limit, clarify how attached and detached garages are treated before finalizing plans.
Basements can be a path to add usable area without increasing FAR when local rules exclude fully or partially subterranean space below a height threshold. Site conditions such as groundwater, drainage, and mature trees can affect feasibility. Confirm both code definitions and engineering requirements early.
Approvals and timelines
If your project complies with zoning standards, you typically proceed via ministerial building permits. Projects that exceed FAR or lot coverage, or that need other exceptions, usually require discretionary review such as a variance or design review, which can add time and community input.
Los Altos places emphasis on neighborhood character, so massing, rooflines, and second‑story stepbacks often come under design review. Expect neighbor notifications and possibly public hearings if you seek exceptions.
Also plan for other constraints that interact with your numbers, such as tree protection, stormwater and grading rules, and any neighborhood overlays or historic considerations.
Strategies to maximize space
- Put more area on upper floors to meet lot coverage while staying within FAR.
- Explore a basement where allowed and feasible to gain usable space with limited FAR impact.
- Use design elements that may be excluded from FAR, such as certain open porches, if the local code allows.
- Right‑size the garage and consider placement to minimize footprint while meeting daily needs.
- Evaluate an ADU based on current state rules and Los Altos standards for added flexibility.
- Work with an architect who knows Los Altos measurement conventions and design review expectations.
For buyers: assess future potential
- Confirm zone, setbacks, FAR or maximum floor area, and lot coverage before you write an offer.
- Ask Planning about ADU potential under current city and state rules.
- Review site features that affect buildability, including trees, slope, and drainage.
- Factor the property’s expansion potential into valuation and long‑term plans.
For sellers and homeowners
- Measure your existing floor area and footprint using local definitions before you design an addition.
- Understand that variances are not guaranteed and require special findings, time, and public input.
- Document what is included in reported square footage, such as garages or ADUs, to avoid confusion in marketing.
- Invest in design quality and context‑sensitive massing to support approvals and market appeal.
Quick feasibility checklist
- Confirm your zoning and development standards with Los Altos Planning.
- Get a current survey or plot plan with lot area, existing footprints, easements, and trees.
- Calculate current floor area and lot coverage using Los Altos measurement rules.
- Clarify how garages, basements, porches, and ADUs count toward FAR and coverage.
- Schedule a pre‑application meeting to understand required approvals and timelines.
- Retain an architect or planner experienced in Los Altos review processes.
Common mistakes to avoid
- Relying on generic FAR percentages that do not match your zone.
- Ignoring setbacks and height, which can block a concept that fits on paper.
- Assuming an ADU will not count toward limits without checking local rules.
- Overlooking tree protection, grading, or stormwater requirements.
Ready for next steps
If you want a confidential, property‑specific roadmap, bring your parcel details and we can help you frame options, confirm limits with the City, and align scope, budget, and timeline. For tailored guidance on buying, selling, or planning improvements in Los Altos, connect with Stephanie Von Thaden.
FAQs
How do FAR and lot coverage work in Los Altos?
- FAR controls total floor area relative to lot size, and lot coverage controls the roofed footprint at grade. Los Altos applies both through its zoning ordinance by residential zone.
Where can I confirm my property’s FAR and coverage limits?
- Check your parcel’s zone in the Los Altos municipal code and zoning map, or request a zoning verification from the Planning Division for official confirmation.
Do ADUs count toward FAR or lot coverage in Los Altos?
- It depends on local code within state ADU laws. Many limits are restricted by state rules, so verify with Los Altos Planning for your specific site.
Does my garage count toward FAR and coverage?
- Garages commonly count toward lot coverage. Whether they count toward FAR varies by local definitions, so confirm treatment of attached and detached garages with the City.
Can I use a basement to add space without exceeding FAR?
- In many cities, fully subterranean basements below a height threshold are excluded from FAR. Feasibility depends on Los Altos rules and site conditions such as groundwater and trees.
What if my concept exceeds the allowed FAR or coverage?
- You will likely need discretionary approvals such as a variance or design review, which require findings, add time, and are not guaranteed. Design revisions are often the faster path.
