Free written scope consultation - allowances, timeline, and change-order rules on paper before a single trade is scheduled
Before
After
Before
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Before
AfterTrusted Home Additions & ADU for Palo Alto Homeowners
Adding square footage to a Palo Alto home means navigating Santa Clara County’s ADU ordinance, Palo Alto’s specific setback rules, and the reality that land here costs too much to waste on a plan that doesn’t pencil out. Since 2007, Rowan Construction Group has delivered over 4,000 projects across the Peninsula, every one with a written price before work started and a documented photo record when the crew left. We build Home Additions & ADU in Palo Alto in Old Palo Alto, Professorville, and the Ventura neighborhood regularly, and we know which plans the city’s planning department flags for revision. Call (650) 446-9092 to schedule a free estimate with a written scope and flat price.
What Our Home Additions & ADU Service Includes
ADU Design & Permitting
An accessory dwelling unit in Palo Alto requires compliance with the city’s 2017 ADU ordinance update and California’s statewide SB 9 and SB 10 provisions, which set maximum unit sizes, parking exemptions, and owner-occupancy rules that change by zone. You need this service when you’re converting underused garage space or building new to generate rental income or house family, and the permitting timeline can stretch six months if the preliminary drawings miss a fire separation detail or utility capacity calculation. At Rowan Construction Group Palo Alto, we prepare the full permit package including site plans, structural calculations, and Title 24 energy compliance, and we flag Palo Alto’s common sticking points early - like the requirement for independent electric service meters on rental ADUs over 500 square feet - so the plan moves through planning in one cycle, not three.
Garage Conversion ADU
A garage conversion ADU restructures existing footprint into livable space, which in Palo Alto typically means raising a low slab to meet ceiling height minimums, insulating walls that were never designed for thermal performance, and routing new plumbing through concrete that may sit on expansive clay soils common to the Midpeninsula. You need this when your two-car garage stores bikes and holiday decorations while your mortgage payment climbs, and the fastest path to rental income is using structure you already own. Our crews in Palo Alto have converted dozens of garages in the Green Gables and Duveneck areas, and we document the existing slab condition with photos before we cut, because a cracked or unlevel foundation discovered after demolition is the change order that kills budgets. Under Clause 1 of the Haven Standard, that written price you receive before we start includes the foundation assessment, so you’re not surprised.
New Detached ADU
A new detached ADU is a ground-up structure on your property, separate from the primary residence, which in Palo Alto triggers design review in some R-1 zones and always requires compliance with the city’s 450-square-foot minimum lot coverage rules that can push the unit toward the rear property line. You need this when your lot has usable backyard space - common in the larger parcels of Barron Park or the foothill neighborhoods near Foothill Expressway - and you want rental income without sharing walls. We handle the full build, from geotechnical report to final certificate of occupancy, and we specify brands like Toto for our Home Additions & ADU in Redwood City bath fixtures and Sterling for shower enclosures because their lead times are predictable and their warranty terms are written, not implied. Every new detached ADU we quote in Palo Alto includes the full utility trenching cost, not a placeholder, because running sewer and water to a rear unit across a 150-foot lot is not a minor line item.
Junior ADU & Interior Conversion
A junior ADU, or JADU, is created entirely within the walls of an existing home, requiring a separate entrance, efficiency kitchen, and internal connection to the main residence that can be locked off - Palo Alto allows JADUs up to 500 square feet and does not require additional parking if the unit is within the existing footprint. You need this when you have a large ground-floor bedroom, a finished basement with separate access, or a wing of the house that’s become storage, and you want to house family or generate partial rental income without building new. Our Palo Alto crews have converted first-floor offices and former in-law quarters in the Community Center and Old Palo Alto neighborhoods into compliant JADUs, and we always verify that the existing HVAC can handle the new kitchen load before we quote, because adding a mini-split after the fact is the kind of unpriced change order we don’t allow. Under the Haven Standard, if the load calculation shows we need supplemental heating or cooling, it’s in the written price from day one.
ADU Site Prep & Utilities
ADU site prep and utilities covers the work that happens before walls go up: demolition of existing structures, grading for drainage compliance, trenching for sewer lateral extensions, upsizing electrical service panels, and gas line routing that may require PG&E coordination taking eight to twelve weeks in Palo Alto’s queue. You need this as a standalone service when you’ve received permits but your general contractor lacks the excavation or utility trade licenses, or when you’re managing the build yourself and need a licensed contractor for the regulated portions. Rowan Construction Group holds the licenses for earthwork, plumbing, and electrical in California, and our Palo Alto crews document every utility trench with photos showing depth, bedding material, and slope - the documentation that passes PG&E inspection on the first visit and protects you if a future property sale triggers a records request.
Room Additions
A room addition expands the conditioned footprint of your primary residence, whether that’s a master suite extension, a family room bump-out, or a ground-floor bedroom for aging-in-place - in Palo Alto, where median home values sit well above regional averages, adding 400 square feet of functional space often returns more value than selling and buying larger. You need this when your household has grown but your lot doesn’t justify a detached ADU, or when you want to stay in your school district and neighborhood rather than absorb transaction costs and a higher property tax base. We build room additions with structural continuity as the priority: matching foundation type, tying into existing roof lines without valleys that leak, and specifying windows from our vetted brand list that match the thermal performance of your existing units. In Palo Alto’s climate, where morning fog and afternoon sun both hit hard depending on elevation, we specify Schluter waterproofing membranes at all wet-area transitions because the detailing prevents the mold and rot that destroy additions in their fifth year, not their first.
Second Story Additions
A second story addition doubles your vertical footprint, which in Palo Alto means structural analysis of a foundation poured in the 1950s or 1960s for single-story loads, and coordination with the city’s historic review if you’re in a designated district like Professorville or the Ramona Street area. You need this when your lot coverage is already maximized but your family needs bedrooms, offices, or a primary suite above the noise of ground-floor living. Our structural engineer evaluates the existing footing depth and rebar placement before we quote, because reinforcing a perimeter foundation in Palo Alto’s sandy-loam soils is not a contingency item - it’s a known cost that belongs in the written price. We also coordinate the temporary relocation of your electrical service and the shoring of your first-floor walls, both documented with photos at each stage so you have evidence of structural integrity, not just our word.
Sunrooms & Enclosed Patios
A sunroom or enclosed patio converts outdoor living space into year-round conditioned area, which in Palo Alto’s climate means designing for summer heat gain through south-facing glass and winter condensation on single-pane walls that weren’t meant for thermal performance. You need this when your patio overlooks a backyard you’ve invested in - Japanese maples in Old Palo Alto, olive groves in the foothills - and you want to use that view in January without wearing a coat. We specify insulated glass units with low-E coatings and thermally broken aluminum frames, and we always verify that your existing HVAC has the capacity for the new load or we size a dedicated mini-split and include it in the written quote. The Haven Standard requires that the price covers the full enclosure, not just the structure, because a sunroom that needs a space heater from Costco is not a finished room.
What happens when you call
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A real person answersNo phone trees - you reach a local pro.
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You get an upfront price rangeHonest numbers before anyone is dispatched.
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A background-checked tech heads outLicensed & insured, dispatched right away.
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You approve before work beginsNothing starts until you say go.
Brands We Service for Home Additions & ADU
We’ve installed Toto toilets and washlets in dozens of Palo Alto ADU bathrooms, specifying their Drake and Ultramax II lines for rental units because the flush performance handles the low-flow requirements without callbacks, and the parts availability means a flapper or fill valve replacement doesn’t turn into a two-week wait. In master suite additions across Los Altos and Mountain View, we’ve used American Standard’s Champion series where the homeowner wants the same Toto reliability at a different price point, and we keep both brands’ rough-in dimensions on file so your plumber isn’t improvising on installation day.
For wet-area waterproofing in room additions and bathroom expansions, we specify Schluter-Kerdi membrane systems, which we’ve installed in over 200 Peninsula projects since 2015. The fleece-backed sheet membrane bonds to modified thinset and creates a continuous waterproof plane behind tile, which matters in Palo Alto’s older homes where the original construction didn’t include any membrane at all. Whether your fixtures are Toto, American Standard, Sterling, or another make, and whether your waterproofing is Schluter or a competing system, we can service, replace, or upgrade it - and we’ll name the brand in your written quote, not hide behind a generic “tile installation” line item.
Before
AfterSigns You Need Home Additions & ADU Right Now
- Your household has outgrown your floor plan but your mortgage rate locks you in place. In Palo Alto, where many homeowners refinanced at sub-3% rates between 2020 and 2022, selling to buy larger means absorbing a 6%-plus rate on a more expensive property. A room addition or ADU rental income can solve the space or cash-flow problem without triggering a move that costs six figures in transaction fees and higher interest.
- Your garage stores nothing of value while your property tax bill climbs. Palo Alto’s Proposition 13 protections mean your tax base stays low, but the bill still grows with assessments and bond measures. A garage conversion ADU generates rental income - often $2,500-$3,500 monthly for a studio in Palo Alto’s market - that offsets ownership costs without altering your primary residence.
- You’re navigating multigenerational care without separate living space. Adult children returning from graduate programs, aging parents needing proximity but independence, or a nanny who needs on-site housing all strain a single-family floor plan. A JADU or detached ADU creates legal, separate space with a kitchen and bath, which is the difference between a sustainable arrangement and one that frays in six months.
- Your foundation or slab shows cracking, settling, or water intrusion. In Palo Alto’s Baylands-adjacent neighborhoods and the clay-heavy soils near Matadero Creek, foundation movement is progressive - the crack that was hairline in 2022 is structural by 2025. If you’re considering any addition, the foundation assessment must happen first, because building new on compromised ground is the project that doubles in cost.
- Your permit research has stalled on a technical requirement. Palo Alto’s planning department receives hundreds of ADU applications annually, and the most common rejection is incomplete utility documentation - sewer lateral capacity, electrical service size, or gas line pressure at the property line. If you’ve been circling the same checklist for months, you need a contractor who prepares the full submittal, not one who hands you a brochure and says “call when you’re permitted.”
Our Home Additions & ADU Process - Step by Step
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Site evaluation and written price. We visit your Palo Alto property, photograph the existing conditions, measure for accurate as-builts, and discuss your goals - rental income, family housing, resale value, or aging-in-place. Within five business days, you receive a flat written price with a detailed scope, brand specifications, and a timeline. Under Clause 1 of the Haven Standard, no work proceeds until you have this document and have signed it. This is not an estimate that shifts; it is the price you will pay, with change orders required only for changes you initiate.
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Permit package preparation and submission. Our drafter prepares site plans, floor plans, elevations, structural calculations, and Title 24 energy documentation specific to Palo Alto’s submittal requirements. We coordinate with the city’s planning and building departments, respond to correction notices, and revise drawings as needed. You receive copies of every submittal and every city response, so you know where your application stands without calling us.
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Pre-construction documentation and scheduling. Once permits issue, we photograph the existing conditions - foundation, utilities, adjacent structures, landscaping - to establish a baseline for any dispute about damage or pre-existing conditions. We schedule PG&E disconnects and reconnects, order long-lead materials like windows and Toto fixtures, and confirm your start date with a text message, not a phone promise. The crew assigned to your project is background-checked and uniformed, and their names appear in your pre-construction packet.
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Construction with documented visits. Our crew works on your property with daily cleanup and weekly progress photos delivered to you by text or email. Every visit includes a documented photo record showing what was done, what was found, and what comes next. If we encounter unexpected conditions - a buried oil tank, a sewer line at half the expected slope - we stop work, photograph the finding, and present a signed change order with options before proceeding. No work continues on a change until the change order is signed; this is the discipline that has kept our projects within a few percent of the agreed price since 2007.
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Final inspection, walkthrough, and warranty documentation. We schedule all required inspections - building, electrical, plumbing, fire - and accompany the inspector to document any corrections immediately. After final approval, we conduct a walkthrough with you, using a checklist that covers every item in your scope. You receive a written warranty, the complete photo record, and a final invoice that matches your signed price plus only those change orders you approved. The 365-Day Done Right Promise begins at this moment: if anything we built is not done right, we make it right, backed by the terms page we provide, not a handshake.
How Much Does Home Additions & ADU Cost in Palo Alto?
A typical home addition in Palo Alto runs $45,000-$130,000 depending on whether you’re enclosing a patio, adding a ground-floor room, or building a second story with structural reinforcement. ADU construction costs more - $90,000-$220,000 - because it requires full kitchen and bath infrastructure, separate utility connections, and independent HVAC. A garage conversion ADU sits in the middle at $30,000-$80,000, assuming the existing slab and walls are salvageable and you’re not extending utilities across a large lot.
Several factors move the price within these ranges. Foundation condition is the largest variable: a slab that needs replacement adds $15,000-$35,000 before walls go up. Utility distance matters - running sewer 120 feet to a rear detached ADU in a large Palo Alto lot requires trenching, bedding, and inspection that a 20-foot garage conversion avoids. Finish level affects cost significantly: American Standard fixtures versus Toto, Schluter membrane versus standard shower pan, custom cabinetry versus KraftMaid semi-custom. We specify brands and materials in your written quote so you know exactly what the price includes.
To avoid overpaying, get a written scope that names brands, specifies square footage, and includes utility costs as line items, not contingencies. Beware the contractor who quotes a per-square-foot price without seeing your property - in Palo Alto’s varied terrain, from the flatlands near 101 to the hillside lots off Page Mill Road, site conditions override any rule-of-thumb calculation. Our free estimate includes all of this documentation, and we offer a Free Second Opinion on any competitor’s written estimate - bring their quote and we’ll review it line by line at no charge, identifying what’s included, what’s omitted, and where the price might shift once work starts.
What’s included in our free estimate: a site visit, measured drawings, preliminary structural assessment, utility routing plan, permit timeline, flat written price with line-item breakdown, and brand specifications. Call (650) 446-9092 to schedule.
Home Additions & ADU Near Palo Alto - Our Service Area
We build home additions and ADUs throughout the Midpeninsula, with crews regularly working in Los Altos - where larger lots favor detached ADUs near the village center - and Mountain View, where the city’s streamlined ADU program has produced consistent permit timelines. Our service area extends to Sunnyvale, Woodside, Cupertino, Emerald Lake Hills, Redwood City, San Carlos, Santa Clara, Fremont, and Campbell, with typical response times of one to three business days for initial site visits depending on current project load. Whether you’re in Palo Alto’s Old Palo Alto neighborhood or considering a second story addition in a nearby community, the same crew standards apply: background-checked, uniformed technicians with a documented photo record on every visit. Visit our home page for a full overview of our seven trades and the Haven Standard that governs each one.
Serving Palo Alto, CA - Our Local Coverage Area
We’re based in the Palo Alto area and know this community well. Use the map below to see our service coverage - if you’re nearby, we can almost certainly help.
Frequently Asked Questions - Home Additions & ADU in Palo Alto
A home addition expands your primary residence - adding a room, second story, or enclosed patio - while an ADU (accessory dwelling unit) is a separate living space with its own kitchen, bath, and entrance, either attached or detached from the main house. In Palo Alto, ADUs are governed by state law and local ordinance that sets size limits, parking rules, and owner-occupancy requirements that don’t apply to room additions. Call (650) 446-9092 and we’ll walk through which option fits your lot, your goals, and your budget - estimates are free.
A room addition typically takes three to six months from permit to completion, while an ADU runs six to twelve months depending on complexity, with permitting alone consuming two to four months in Palo Alto’s current queue. Detached ADUs and second story additions take longer due to foundation work and utility coordination with PG&E. We include a timeline in every written quote, and we don’t start construction until permits issue, because building without approval risks stop-work orders that add months.
ADU construction in Palo Alto costs $90,000-$220,000 for a detached unit, $30,000-$80,000 for a garage conversion, and $45,000-$130,000 for attached or interior conversions depending on size and finish level. The price includes design, permitting, construction, fixtures, and utility connections - we don’t quote without seeing your property because foundation condition and utility distance are too variable. Call (650) 446-9092 for a flat written price based on your specific site - estimates are free, and we offer a Free Second Opinion on any competitor’s quote.
Yes - we’ve installed Toto, American Standard, and Sterling fixtures in hundreds of Peninsula projects, and we specify Schluter waterproofing membranes as standard in all wet-area additions and ADU bathrooms. We keep rough-in dimensions, warranty terms, and lead times current for all four brands, and we name the specific product line in your written quote so there’s no substitution without your approval. If your existing fixtures are another brand, we can match or upgrade them - the brand is your choice, and the price reflects your selection.
Home additions and ADU construction are planned projects, not emergencies, so we don’t advertise same-day dispatch or emergency availability for this trade - no one frames walls or pours foundations overnight. However, if you have an urgent safety issue related to an existing structure, such as a collapsed beam or exposed electrical after demolition, our live answering service takes calls 24/7 and routes emergencies to the appropriate crew. For planned work, we schedule site visits within one to three business days and deliver your written price within five business days of that visit.
Every home addition and ADU carries our 365-Day Done Right Promise: if it is not done right, we make it right, backed by a written terms page, not an asterisk. This covers workmanship, materials, and installation for one year from completion, with specific terms for each trade involved - framing, electrical, plumbing, roofing - so you know exactly what’s covered and for how long. We also pass through manufacturer warranties on all fixtures and materials, and we register those warranties in your name where the brand requires it. The warranty documentation is part of your closing packet, not something you have to request later.
Gather any existing property surveys, recent appraisal documents, or prior permit records you have - these accelerate our preliminary assessment. Clear access to the work area, including garage, basement, or backyard, so we can photograph existing conditions and measure accurately. Prepare a rough idea of your budget range and your primary goal - rental income, family housing, or resale value - so we can recommend the right scope, not just the largest one. We’ll handle the rest: site measurement, preliminary structural assessment, utility routing plan, and the flat written price delivered within five business days. Call (650) 446-9092 to schedule - estimates are free, and there’s no obligation to proceed.
Schedule Your Home Additions & ADU Service in Palo Alto Today
Call (650) 446-9092 to schedule your free estimate. You’ll receive a site visit, measured drawings, and a flat written price with line-item scope and brand specifications - no “call for a quote,” no placeholder numbers, no surprises once work starts. Our live answering service takes calls 24/7, and our Palo Alto crews are background-checked, uniformed, and equipped with the documentation standards that have kept Rowan Construction Group projects within a few percent of the agreed price since 2007.
Written by Grant Rowan, Owner at Rowan Construction Group, serving Palo Alto since 2007.