ADU design cost

ADU prices are all over the map. I've personally visited basement ADUs that cost $20K, and an ADU above a garage that cost north of $400K. So, it's not a straightforward task to explain how much an ADU cost to build In places like the Bay Area or Seattle the average cost for an ADU is closer to $350,000 or more. On the higher end of the scale, if you are looking for a premium luxury ADU with the top of the line systems and appliances, high-end materials, and a premium design, you can look to spend $400,000 to $500,000 or even more City fees will average* at: $4,000.00-$8,000.00, for example a 499 square foot, 1-bedroom, 1-bathroom unit cost is approx. $4,000.00. Construction labor and material will average* at $200-$250 per square foot, for example a 500 square foot, 1-bedroom, 1-bathroom unit average cost is $99,800.00-$124,750.0 ADU Cost Calculator. Instant ADU cost calculator. Fill in the information below and the calculator will show you your estimate right away. * Required. 1. What type of lot is your ADU on? Levi Design Build is full-service design & build company specializing in ADUs, garrage conversions and home additions Your Current Mortgage + Construction - Rental Income. $ 2,279. ADU Estimator is proudly provided by: Meredith Stowers. 619-520-1018

Hiring a firm to design and obtain permits for your ADU can cost anywhere from $4,000 to $10,000 and up. While this may seem like a lot upfront - architectural designers are trained to make every square foot count Area: 1060 sq.f. Footprint: 24'-41/2 x 40-10. ADU design featuring a welcoming, full width, front porch. Its minimal footprint makes it an ideal budget choice for those wanting. At just 1060 Sf the floor plan delivers a little bit of everything two Bedrooms, a kitchen, two baths, and ample living space with no wasted space In Bay Area all-in architect fee for me to build a detached ADU (800 sq. ft.) was $12K (inclusive of engineering and title 24). Permit fees total were roughly $5K. Hope this provides a reference from another expensive area in CA. More detailed breakdown below The design features a large, welcoming and protective canopy. The plan packs numerous features and functions into a 770 sf envelope which is easily expanded for non-ADU uses.. The ground floor open floor plan features two connections to the outdoors: from the living room at the rear and the side conveniently adjacent to the kitchen 7 Smart ADUs and Additions That Cost as Little as $18K. From a shingled studio in Minneapolis to a two-bedroom guesthouse in L.A., these backyard projects are something to emulate. Whether you're in need of a guesthouse, art studio, home office, yoga practice space—or all of the above—a home addition or backyard ADU can do the trick

Attached Garage Conversion

So if the total cost to build your ADU was $400,000 you could expect to spend $16,000 to $24,000 to get the design, budget, selections, plans, structural engineering & energy calculations completed & ready to submit to the local building department ADU design cost —— $7- Minimum design fee for garage conversion starts from $3500.00 (7 or 8) ADU permit cost —— $8 ADU construction cost —- $150 - today average price per Sq

Rather, overall cost is more helpful. Generally speaking, the ADUs we build (particularly the stand-alone variety) start at a couple hundred thousand dollars in construction cost, with that cost increasing depending on design choices about finishes, fixtures, and building components Pre-made ADU design and construction plans will save you thousands of dollars and weeks of waiting where if you hire an architect/designer for custom plans. All plans include estimates on cost to build, so you can compare the costs from contractors by collecting their bids. And of course save tons of money on architects and designers Typically permitting fees for an ADU fall around $6-$10k, but the additional amount here reflects the fact we had to upgrade the water supply branch & meter size at the 2015 Portland Water Bureau pricing. Excavation - $14,000 Around a 650sf slab area including the exterior decks The Cost of Building: While construction costs will depend on the design of the home and the quality of the building materials, the average you can expect is about $100 to $200 per square foot. If you get a 500-sq-ft ADU floor plan, you can expect the construction costs to be roughly $50,000 to $100,000 Even then we don't really see the cost of a custom designed ADU dropping below $175,000 when all is said and done, and even to achieve that number it would have to be a small and very simple design. It is also important to consider that a cost per square foot calculation is not a great way to determine the cost of an ADU

So naturally, design, permitting, and construction costs will vary from project to project. In the Bay Area, you can expect a 650-square-foot ADU to cost around $350,000 on average to construct where a 350-square-foot ADU will likely cost around $225,000 to build Contact. 0 items. $0. ADUdesigns.com is a collection of architect created, space efficient, designs for Detached ADUs, Cottages and Bungalows. From around 380 sf to 800 sf (and occasionally larger) designs are easily expanded or modified for non-adu use. Traditional designs (president and VP names) and Contemporary styles (tree and shrub names) Summit Series: Design Yours Today. Explore the Studio Shed Summit Series, our premieru0003 ADU solution. Combine different exteriors & interiors to match your personal style. Price starting at $28,700. ~$113-240+/square foot (price varies by design An accessory dwelling unit is a fully functional living space that can fall into one of three categories: The intended use has a major design and planning impact A small structure costs. Rost Architects ADU Design. Cost of Building an ADU. A great study was performed by the county of Santa Cruz on the cost to build an ADU in their area. The costs will vary throughout the state, but their analysis found that the average cost to build an ADU unit was roughly $150,000

Calculating the Costs of Accessory - Building an AD

The Truth About ADU Costs. Accessory dwelling units are increasingly popular throughout California as counties are encouraging in-building to create more housing. If you're considering investing in an ADU in the Bay Area, no doubt cost is one of the most important factors in your decision-making process. Because this is a significant. ADUs are notoriously difficult to design! Before you hire an ADU designer, answer these critical questions before you invest in the design process

How Much Does An ADU Cost? — Modern ADU Plan

  1. San Mateo County: One Stop Shop Program - Provides no-cost support from Hello Housing with the design, permitting, and project management involved with building an ADU. Monterey Bay: My House My Home Program - Creates affordable ADUs for low-income senior homeowners in the Monterey Bay area
  2. Question 1: How much does it cost to build an ADU? This is difficult to answer without the specifics of a project but we can at least give you some insight into typical costs of a new construction, detached ADU in Portland, Oregon. Construction $225,000 to $350,000+. Design $17,000 to $30,000
  3. An Accessory Dwelling Unit (ADU) is a self-contained living unit that is usually smaller than the main home on the same property. It contains a kitchen, bathroom, and a place to sleep. They can be attached to the main home or a separate detached building. They can also take the form of a Junior Accessory Dwelling Unit (JADU), which is a unit up.
  4. A small 450 square-foot ADU generally starts around $300,000 to design and build. Large 1,200 square-foot ADUs begin at approximately $475,000. With the median home price in San Diego at over $637,000, opting for an ADU is a far more affordable option. A portion of those costs is made up of fees
  5. An ADU can be done in a basement, over a garage, or a separate attachment to your main home. Depending on your location preference and size will affect the cost. The average price you can expect to pay for an attached ADU is around $75 per square foot. Another cost that you want to take into consideration is the permit and licenses in your area.
  6. 5 Hidden ADU Costs to be Aware of Since the state of California passed some new, friendlier rules in 2020 , ADUs have massively grown in popularity. The return on investment is incredible if you rent out your new granny apartment
  7. Estimate ADU Fees and Costs. First, review the Financing Guide to learn about costs associated with creating an ADU. Next, estimate County permit fees, hard and soft construction costs, and cash flow over time in three easy steps using the County's Estimator. You will need to enter your Assessor's Parcel Number (APN) into the Estimator

ADU Development Cost - Levi Design Buil

ADU Cost Calculator - Levi Design Buil

  1. 9 ADU Plans to Choose from: MINI UNIT PLANS 250 Sqft to 399 Sqft. The Mini's are our most popular home sizes right now, and for good reason. They are small enough to fit on smaller inner city lots and their size makes them affordable to a much larger group of people
  2. Accessory Dwelling Unit (ADU) Floor Plans & Designs. The best detached auxiliary / accessory dwelling unit (ADU) floor plans. Find granny pods, garage apartment plans & more! Call 1-800-913-2350 for expert support. Read More. Read Less. Filter
  3. This ADU serves as a guest house/yoga studio and sits over an existing garage. Fusion Landscape Design worked with PATH to remake the backyard into a grown-up playground. Under the stairwell sits a tiny custom cedar sauna and an outdoor shower—just a literal hop, skip, and jump away from the sprawling in-ground eight-by-ten-foot hot tub
  4. THE BENEFITS OF OUR ADU FLOOR PLAN DESIGNS. Increase the value/equity of your house. We pass the LA Plan Check on the 1st or 2nd submittal. We come to your home to measure. We cover delivery cost to your home. Our designs are rented for more money. We cover the floor plan printing cost ($200-$500 per set) We offer a 5 to 10-day turnaround time
  5. It typically costs more than $125,000 in materials and labor to add a unit. Professional services for architects and engineers are typically 10% of construction costs. City fees range from 6 to 9% of construction costs. Your total cost can range widely depending on the specifics of your lot and project. Your property and project plans affect.

A 484 square foot detached new construction in Portland may have a starting cost of $150K when accounting for the design, permitting, construction, and finish work. So, it is remarkable when a homeowner can develop any ADU for under $60K. Kol: Dan, explain the big picture of the property a bit to start An attached ADU not to exceed 50% of the primary dwelling. The ADU shall be architecturally similar to the primary dwelling in terms of design, building and roofing materials, colors, and exterior finishes. An ADU taking advantage of the four-foot setback provision shall not be allowed to exceed a height of 16-feet 3. How much does it cost to build an ADU? As a general rule, ADUs don't come cheap. Even without the land costs, the cost of construction — and viable ways of paying for it — are limited. The cost will depend on the size and type of ADU, and the local wages. For instance, the city of San Jose, California — one of the more expensive.

ADU Cost Estimator - ADU Design and Constructio

  1. 2. The Design. Although the ADU is smaller compared to the main house, designs affect the total cost of putting up the ADU. Talk to the designing professional for an estimate on how much it will cost to draw the blueprints. A complicated design will cost you much more even in terms of materials. The simple design takes less time and resources.
  2. The cost for an ADU garage conversion can usually range from $80,000-$120,000 depending on the homeowner's requirements. Costs to construct a new accessory dwelling unit can also vary considerably based on size, the number of stories, location, access, but will generally range from $100,000-$400,000. A safe rule of thumb is to assume $250.
  3. e a budget for their project. The cost for building an ADU varies by the scope and quality of the project, and homeowners need to take into consideration the additional cost of permits and other fees, Lisa clarifies.
  4. We are a vertically-integrated firm providing design, engineering, permits and construction services all under one-roof for a true 1-stop shop experience. Our sole focus is ADU's. With 15+ years experience in home development projects in every major city in LA county, we understand real estate, financing, and construction. We are your best.
  5. For larger ADU's over 800sf, the square foot cost may come down because of the economy of scale, if the design and finishes are fairly simple. The range in cost is great because larger ADU's, such as a 1200sf ADU, can be 3 bedroom/2 bath complete homes
  6. A general, ballpark estimate for a 200 square foot interior ADU is about $150,000. Again, this budget number can vary widely depending on the type, design, size, and other aspects of the ADU. The best way to get a ballpark estimate is to talk with your design/build firm about what your specific needs are

Our expert designers create homes that are accessible, space & energy efficient, and add value to your property. Your new ADU can be ready in 6 months. Call 650-383-7468. Most homeowners qualify for streamlined permitting under the new California ADU laws How much does it cost to build an ADU? Cost is difficult to estimate. It is based on the design, materials, finishing and many other variables. In general, a detached ADU is the same price per square foot as a single detached home. As of 2020 that means that the City of Eugene plan (approx. 576 sq. ft.) would be about $115,000 to construct Accessory Dwelling Units (ADU) Construction Services Los Angeles. We at Pre Built ADU, Los Angeles pride ourselves in being the best ADU service providers in Los Angeles and area around. Our craftsmanship and expertise is supported by our years of unparalleled work which is unmatched for. We are fully read on the rules of the state and we abide.

How Much Does an ADU Cost to Build in Los Angeles

Cost-Efficient ADU Plans for your home in California

  1. e the cost that you will have to pay. The design is also the other key consideration that you need to pay attention to as it will significantly affect the cost of the ADU
  2. Building an ADU (Accessory Dwelling Unit) in California Can I avoid Solar my ADU design? Title 24 exceptions? If you want to avoid solar in your ADU design haven't gotten a permit yet, you can't. If the ADU plans were submitted to the permit office in 2019 and your ADU will qualify under the 2019 laws and can avoid Title 24
  3. An ADU, or Second Suite, is a permanent secondary residence on a city lot with a dedicated kitchen and bathroom. Legally, these are referred to as an Accessory Dwelling Unit (ADU) and they come in several different forms. ADU's are often referred to by an assortment of names, including granny flat, mother-in-law suite, in-law suite, above.
  4. ADU PLANS. A good set of design and building plans are absolutely critical to a successful project. Inexperienced ADU Architects or jack-of-all-trades designers will cause project delays and tens of thousands of dollars of additional costs
  5. When pricing out how much converting or building an ADU will depend on the type of ADU you will be either building or converting.With an interior ADU the cost will typically start around $60,000 and go from there depending on the quality of the materials, size of the room(s), and extras you may decide on like built in shelves and such. Detached.

Los Angeles ADU design cost - biggerpockets

How much does it cost to build an ADU in Los Angeles? During our free consultation and design process, we can figure out the cost for your ADU or garage conversion. We are the best ADU Contractor in Los Angeles because we streamline the process of building an ADU by providing you with full service design, permitting and construction An ADU attached to a primary dwelling may be up to 50% of the size of the single-family residence, up to a maximum of 1,200 square feet. An ADU detached from the single-family residence may be up to 1,200 square feet, regardless of the size of the residence. An Accessory Dwelling Unit creates additional space for your growing family 20 classes covering every facet of ADU development from ADU costs to financing, design to permitting, and construction to rental management approaches; 40+ quick tips from out in the field covering tips on ADU specific building informatio

An Accessory Dwelling Unit (ADU), also known as a granny flat or guest house, are attached or detached residential dwelling units, on the same lot as an existing single -family dwelling unit. An ADU must include complete independent living facilities for one or more people. A sleeping area, kitchen for cooking, and sanitation must all be. Featuring ADU policies and projects from Austin, Texas; Denver, Colorado; Oakland, California; and Washington, D.C., this 113-page Accessory Dwelling Units design catalog contains information about financing and budgeting for an ADU project as well as visuals that show how ADUs can be easily designed to serve people of differing ages and abilities ADU Design-Builder Profile: UDU Design LLC. Katharina and Paz teamed up to create UDU Design, a design-build company devoted to creating accessory dwelling units (ADUs) - or Urban Dwelling Units (UDUs) as Katharina and Paz call their own brand of ADUs. Over the past 3 years UDU Design has created 8 ADUs in Oregon For any questions, contact the Affordable Dwelling Unit at 703-737-8043, Monday through Friday from 8:30 a.m. to 5:00 p.m. ADU staff is conducting virtual intake sessions instead of in-person sessions. If you have been scheduled for an intake session, directions on how to virtually participate will be e-mailed to you in advance of the intake. Connect 2. We've reinvented 640 square feet to offer a modern Accessory Dwelling Unit (ADU) designed for maximum comfort. Enter the space and be greeted by an expansive living room that seamlessly flows into the kitchen and dining room. A generous bedroom ensures that guests or renters will feel at home in this small structure that feels.

Garage Converted into 340 Sq

ADU Design

residents will be able to access the pre-approved designs on the ADU standard plan website. the designs will help simplify, expedite, and reduce the cost of the overall permitting process by. Forbes recently called 2020 The Year of the ADU. Due to a heavy push for affordable housing—perfectly timed with state regulation adjustments and advancements in construction technology—building additional structures and living spaces will be easier for homeowners this year. From prefab to design-build, the options are endless for Californians who want in-law units, guesthouses, or [ The ADU Homes team has more than two decades of experience in the home building, design, finance, and technology industries: ADU Homes offers a convenient one-stop-shop for diverse ADU needs. The firm brings a novel approach to building ADUs, using efficiency and innovation to deliver value, cost savings, and a hassle-free building experience. Dear Ventura ADU Specialists Family: We are doing all we can to make sure we take care of you, our employees, and your projects. With that said, we are following all regulations set by the California Contractors Board, the Centers for Disease Control and Prevention (CDC), and our local jurisdictions 12 reviews of JZ Plans Architecture Design It's very lucky to have Justin to design our ADU. We hire Justin on 4/2019 and the permitting process is very smooth. He is very honest and let us know a lot of the construction cost before the design approval by city which saves us a lot of money. He is well experienced and gives us a lot of useful suggestions

7 Smart ADU and Additions That Cost as Little as $18K - Dwel

An ADU is between 300 and 1,200 square feet on average. Again, the price per square foot can range based on the local economy. However, on average, you can budget for $200-$250 per square foot and up for a well designed and quality ADU. So an ADU that is 700 square feet may start at $140,000-$175,000 to build which would result in an architect. Total cost including design & construction: $250,000 and completed in 14 weeks! 1. Design, planning, permits, set up, and project management fees (including demolition, dumpster, satellite toilet, and clean up) $38,500. The best part about working with a design-build company is they take care of everything 3. Detached ADU (ground up design) - New Construction. ADU Conversion of Existing Garage: 400SF - 500 SF. A garage conversion is the cheapest of all ADU types because the framing is already existing, but it may still need some work. The cost of construction is the lowest when the garage is at the front of the lot with easy access to the sewer.

Accessory Dwelling Unit (ADU) Building Cost Guide

Accessory Dwelling Unit How-To | Page 1 of 7 Accessory Dwelling Unit (ADU) Design Construction Cost Estimates an 800 s.f. ADU would cost $5262 for permitting and certification. All administrative zoning permit decisions may be appealed to the appropriate municipal panel (typically the development review board or zoning board of. What will my ADU cost? Factors such as size, location and finish will greatly impact your project's cost. A simple ADU conversion could cost around $60k, while a new detached ADU could be $500k+. Can I sell my ADU? No. ADU's run with your primary property/dwelling and cannot be sold separately ROST ARCHITECTS | LUXURY ACCESSORY DWELLING UNITS. Cut out the design time with our ready-made construction documents by Rost architects. Select one of our plan sets or contact us for customization. Preliminary Site Analysis Package. 1,000.00 DRAWING YOUR DESIGN ESTIMATING THE COST. BUILDING YOUR ADU 4 BEFORE YOU BEGIN. HIRING & WORKING WITH A CONTRACTOR Interior ADU Unit in finished attic Interior ADU Unit in finished basement Interior ADU Control Districts (ADCD), design review is required for a new structure, changes to the exterior of an existing structure, or demolition. An ADU / DADU (or accessory dwelling unit) is also known by terms like backyard cottage, or in-law suite. Browse our ADU House Plans to build on your land

Calculator - CA AD

The preapproved ADU plans are available in a Universal Design/Accessibility floor plan design option with a step-free entrance, sufficient maneuvering space for a wheelchair in a bedroom, kitchen, entertainment area, and admittance to a full bathroom, and ample room to pass through 32-inch doorways bunchADU offers ready-to-go ADU designs for the Los Angeles area. Bunch Design is a practice that creates high quality modern design with a strong emphasis on the inventive use of materials Accessory Dwelling Unit Floor Plans. Plus Space™ ADUs by Insulspan® is a new line of Accessory Dwelling Units (ADUs) designed to meet the increasing demand for flexible living spaces. A Plus Space™ ADU kit includes our ready-to-assemble SIP structural shell of exterior walls and roof panels. Then, the fun begins It has 2 bedrooms 2 baths and is designed for the owners' son who is disabled and an aid or roommate. Even when things didn't go as expected, Backyard ADUs was there to make it right.. This 525SF ADU is of our S-Line design path. This poolside home has 1 bedroom 1 bath and is now home to the owner's brother Design fees: Plan on between 8-15% of planned construction cost. Design fees vary from firm to firm, and depend on project type and size. We bill hourly for architectural services. Once we understand the planned scope of work, we can advise on projected fee amount

Los Angeles ADU Architect - Floor Plans For Garage

How Much Does it Cost to Build an ADU? Hammer & Han

ADU Look Book. We offer pre-selected interior design packages to choose from so you can easily find a cohesive look that's perfect for your ADU. Check out our curated Looks that work well for rentals or for family members. See LookBoo ADU Costs One of the goals for this project is to build high-quality custom construction at a relatively low cost; partially by making better design decisions, and partially by sourcing materials and labor astutely. Here is a time and cost breakdown of the design phase that I just completed, which amounted to $8,196 In the last two years, the number of ADU applications submitted the Los Angeles Department of City Planning totaled 11,045. That saves costs on design and laying the foundation An Accessory Dwelling Unit aka ADU -aka Granny Flat -aka Companion Unit is a second small dwelling on the same parcel of land as your single-family house. An ADU can be up to 1,200 sq ft and can be built as: Detached stand alone building. Attached to primary dwelling. Converted space within the primary dwelling (Junior ADU

ADU Construction & Design Plans for Sale - ADU Building Plan

Crest Backyard Homes, #1 in affordable accessory dwelling units (ADU). 400-1200sf. Design your own architectural motif. Can be installed in less than 4 months starting at $80,00 With over 20 years in architecture and a decade focused on ADUs before anyone coined it, Inspired ADUs has helped more homeowners than any ADU architects in the Bay Area. Because we're experienced architects, we draw on our skills working with high-end clients on custom homes to deliver the best in ADU design. We don't just give you a. ADU Design Plan #LDC-1921 Design (40) ADU Design Plan #LDC-1921 1053 ft² Styles: Contemporary All plans purchased come with a complimentary cost to build form for collecting contractors bids. Create Your Site Plan 5% off discount. QUESTIONS

Arcadia ADU Architect - Floor Plans For Garage Conversion

How much does it cost to design and build an ADU in

A quick process contributes to reduced fees—and other expenses, like design costs, could also go down. (SDCI) is leading the project and that one ADU design in the survey was by Model. 1 If legalizing an ADU built before Jan. 1, 2020, city must grant 5-year delay of enforcement of non-safety-related building code violations. 2 If an ADU exceeds 25% of the required rear-yard area, it must be reduced to 800 sf for streamlined approval The Benefits of Our Models. Superior ADUs has pre-designed, developed, and engineered these Model ADUs so you don't have to. A great amount of time and money goes into custom designing an ADU from scratch, which can make building an ADU quite costly. Superior ADUs has already developed the plans for each model, so you don't have to spend. Whether you're new to learning about ADUs or ready to begin the process, we have the information you need. Find out what an ADU is, what types of ADUs you can build, and the ways it can support you, your family, and the community. Find out what you're eligible to build, determine your potential costs, and more in our ADU 101 series I highly recommend Design Everest. I engaged with this firm to design my 800SF/450SF ADU. The project was completed flawlessly and on-time. The design that was done was perfect for the site and was exactly what I wanted. The design engineers and supervisors were very easy to work with and efficient. I was so lucky to find this firm

12 Beautiful Granny Pod Ideas That Will Improve the Backyard

How Much Does It Cost to Build an ADU in California

Everything You Need to Know About Building an ADU. Before you map out plans for an accessory dwelling unit on your property, it's important to know the ground rules. We asked city experts and design pros for advice to help you chart a course to the backyard dwelling of your dreams. Hilary Masell Oswald 5280 Home June/July 2020 Accessory Dwelling Units (ADU) in Sacramento. Custom Home Building Experience with Personalized Approach. Sacramento's #1 one-stop shop Design & Build Firm. Superior Materials and Craftsmanship. (916) 970-0047 Here is a link to download the full financial projection. West Los Angeles. 90025. The projected rent for the 1,019 sq. ft. unit is $4,354/month. The all-in cost to build this (fully loaded) ADU is projected at $361,358, which sounds like a lot, but when financed at 90% Loan to Cost, creates a monthly payment of $2,231 If you don't have this height, you can dig out your basement, but be prepared to add $10k-$20k to the cost of the project (or a lot of sore muscles). Exterior Entrance. John Baker's ADU. Your dream basement apartment will need its own exterior entrance from the house. Building a new one will cost you $10k or more COST. What is the total cost for an ADU? It will depend on the size and type of ADU. A new, custom-built detached ADU may cost as much as $250,000. Retrofitting an existing attached garage or basement may cost approximately $80,000 to $150,000, depending on size, existing plumbing, and how you design the space

Detached Bedroom as Tiny Home | Accessory DwellingsTo Encourage More Housing, Mendocino County Offers Free

After a year of development and a 7-month pilot phase, the ADU Standard Plan Program gives homeowners access to 20 pre-approved design options from 10 different firms. By choosing from one of the pre-approved layouts, homeowners can now reduce the LADBS plan check review process from 4 to 6 weeks to as little as one day One way to lower the overall cost of an ADU is to work with a vendor who offers ADU designs that are preapproved by the City. See our Preapproved ADUs webpage for more information. If you're interested in the state legislation on ADUs - what's allowed and where - see the California Department of Housing and Community Development's new. Costs. The number one question we get from clients who want to know about building ADUs is cost. Because you are essentially building an entirely new house—though on a smaller scale—construction costs for a custom ADU built with HDR Remodeling averaged between $400-500k and $800-1000 per square foot in the Bay Area in 2020