Home Addition Design & Permit Drawings in Monterey County
Guest Suites
An attached or detached accessory dwelling unit (also called an ADU) can serve many purposes. You could give your parents their own space while being close by. Your grown kids can have a place to crash for the short-term or long-term, should they need it. An ADU can also provide a source of income if you decide to rent it out. Our experience working with the Planning and Building Departments in Monterey County means you won’t be caught in endless red tape throughout the planning and construction process.
Traditional Home Additions
There’s one thing our home addition clients have in common: they want more space. The function of that new space, however, is up to you. If you want another bedroom and bathroom, we can design the ultimate primary suite. If you want to bump out your kitchen to add a larger pantry and more cabinetry, we can redesign your existing kitchen to flow perfectly with the supplemental space.
If you’re looking for some more office space or a room dedicated to crafting, 3-D printing, or a home gym, we can brainstorm with you to integrate some hobby-specific elements into your room—from custom lighting to built-in shelving and storage solutions. No matter what you need, our design will encompass every detail.
Plus, it’s never been a better time to design an addition for your Monterey County property—the 2025 opening of a new water recycling facility for the Monterey Peninsula offers expanded capacity for additional residential hookups. Contact RDD today to learn more about home addition planning in Monterey County!
Premier Home Addition Planning on Monterey Bay
What a home addition design includes
A complete submittal set is more than a floor plan. For a typical addition we produce:
- Existing conditions — measured as-built drawings of the house as it stands today.
- Proposed floor plans — dimensioned, with wall types, door and window schedules and fixture locations.
- Exterior elevations and building sections — how the addition meets the existing roofline, and how finished height is measured.
- Framing and structural plans — the details your structural engineer’s calculations attach to.
- Title 24 energy documentation — required for every addition, scaled to the size of the work.
- The submittal package — assembled in the format your jurisdiction accepts, so intake does not bounce it back.
On older Peninsula homes, existing conditions is the step people skip and then pay for twice. The original drawings either never existed or stopped matching the building decades ago.
When a home addition needs a permit
Adding conditioned floor area requires a building permit. The question worth asking is not whether you need one, but which reviews you pass through and how long they take.
The 2025 California Building Standards Code took effect January 1, 2026. Compliance is set by the date your permit application is filed, not the date construction starts. Title 24 requirements for additions step up in tiers, roughly at 400 and again at 700 square feet.
In the City of Monterey, four things routinely catch homeowners out:
- Architectural review is triggered by conditions rather than by choice — a lot under 5,000 square feet, a slope over 15%, a new two-story residence, or a second-story addition.
- Story poles are required for construction greater than one story or an increase in height, installed at least 10 days before a decision.
- Windows always require a permit — egress, tempered glazing, weather barrier and energy certification all attach to them.
- Water credits. If the addition adds or relocates plumbing fixtures, the Monterey Peninsula Water Management District enters the approval path and the property must have sufficient credits.
Carmel, Carmel Valley, Pacific Grove and Pebble Beach each run a different process.
Requirements and timelines described here were researched in September 2026 and are typical rather than guaranteed. Verify current requirements with the building department for your jurisdiction.
Building up or building out
Almost every addition on the Peninsula starts here, and lot coverage, setbacks and your existing foundation usually decide it before preference does.
- Building out is simpler structurally, but it consumes yard and runs into lot coverage limits and setbacks.
- Building up avoids the footprint problem, but transfers new load through the existing structure into the existing foundation — so a structural engineer is not optional.
More on whether it is cheaper to build up or out and what a second story involves.
A guest suite with a kitchen, bathroom and its own entrance is not a guest suite to the building department — it is an accessory dwelling unit, reviewed under a separate and more favorable set of rules. If that is your direction, start at ADU design.
What drives cost, and how the process works
Design and drafting fees on an addition move with five things:
- Whether usable drawings of the existing house exist. They usually do not, and measuring is real work.
- Structural complexity — a single-story bump-out on a flat lot versus a second story over an unreinforced 1950s foundation.
- The site. Slope and soils can add a geotechnical investigation.
- Which review track you land in. Building plan check alone is one calendar; design review is another.
- How quickly decisions get made. A layout settled before elevations are drawn costs less than one settled after. More on what drives remodeling costs.
The work itself runs in five steps:
- Consultation — what you want, and what the lot allows.
- Existing conditions — we measure and draw the house as it actually is.
- Concept design — layout options against setbacks, coverage and budget.
- Construction documents — the permit set, with structural and Title 24 coordination.
- Submittal and plan check — package prepared for submittal, corrections answered.
We work throughout Monterey County and into Santa Cruz County. See all service areas, or our kitchen, bathroom, whole-house and contractor services.
Home addition design FAQs
Do I need a permit for a home addition in Monterey County?
Yes. Any addition of conditioned floor area requires a building permit, and depending on your lot and the size of the work it may also require architectural or design review first. In the City of Monterey, review is triggered by conditions including a lot under 5,000 square feet, a slope over 15%, a new two-story residence or a second-story addition.
Do I need an architect for a home addition in California?
For most residential additions, no. California allows a licensed general contractor, a building designer or a drafting firm to prepare the plans for typical single-family work, with a licensed structural engineer providing calculations where required. We are a design and drafting firm, not an architecture firm, and we say so plainly — here is the full explanation.
Can I add a second story to my house?
Often, but it depends on the existing foundation and framing rather than on the design you have in mind. New load travels down through the existing structure, so a structural engineer has to confirm the house can carry it — and if it cannot, foundation and shear work becomes part of the project. More on second-story additions.
Will my addition need structural engineering?
Most will. Anything that removes or modifies load-bearing walls, adds a second story, or spans an opening beyond what conventional framing allows needs an engineer’s calculations to be permitted. We coordinate with your engineer, or bring one in, and the drawings carry their details.
Do I need a geotechnical report if my lot is on a slope?
Possibly. Monterey County generally expects a geotechnical investigation given the region’s seismic setting, but the building official can waive a full report in defined situations — for example a one-story addition of 500 square feet or less on level, undisturbed grade. Slopes of 3:1 or steeper require sign-off from a California Certified Engineering Geologist or registered geotechnical engineer. What triggers a soils report.
Is it cheaper to build up or build out?
Building out is usually simpler and cheaper per square foot, until lot coverage, setbacks or a septic field make it impossible. Building up avoids the footprint constraint but adds structural work below the visible project. The full comparison.
How long does the design and permitting process take?
Design and construction documents vary with scope and with how quickly decisions get made, so we quote a date once we have seen the job rather than a range up front. Plan check is separate and jurisdiction-dependent. Build in time for one round of corrections; it is normal, not a setback.
Do you work with my contractor, or do I need one first?
Either order works. A good share of our work comes through general contractors, so we are comfortable drawing to a builder’s means and methods. If you do not have a contractor yet, a complete plan set is what lets you get comparable bids instead of four estimates for four different projects.
Concept To Plan Submittal, Made Easy
When you work with our building design team in Carmel, you’re not just getting high-quality renovation design services for your home you’re getting a reliable partner who will help see your project through from dream to reality. Contact us today for a project consultation and estimate.