Pro Tips

written by
W. Charles Perry

The ADU ordinance has been around for a few years—take advice from someone who’s been through the process.

Have you been considering adding an Accessory Dwelling Unit but don’t have a clue where to start? Lucky for you, now is the perfect time to begin; local contractors have been through the ups and downs of the process, and are happy to share their plethora of advice. Read on for W. Charles Perry’s (Principal Engineer of W. Charles Perry & Associates) advice on completing the best ADU for your space.

Hire licensed, experienced and local design professionals.
Building in San Francisco is like pitching baseball in the major leagues. An 85-mph fastball that wows crowds in the minor leagues ain’t gonna win games in the city. Any professional you hire must know San Francisco’s planning code, building code, mechanical code, plumbing code, fire code, electrical code, accessibility code . . . and Morse Code to successfully design an ADU here. They will work with the City Attorney’s office and the Assessor-Recorder’s office to create, file, and record notices of special restrictions and Costa Hawkins agreements. They will work with the Public Works Department, the Planning Department, and the Urban Landscape Department to ensure the sidewalks, landscaping, bicycle parking, access, and trash and recycling bins meet current standards. They will file minor encroachment permits and record easements in a manner that they can’t be altered without city approval.

The professionals you choose will work with Historic Preservation to ensure any changes to the façade meet the architectural sensitivities of the period, and the Building Department to correct missing addresses, verify the legality of each existing apartment, and remedy existing Notices of Violation. They will notify neighbors if you have foundation work along the property line and develop methods to protect their property. An experienced professional will know where ancient underground streams are, and know how to waterproof against them. They will deal with zero-lot line niceties, like shared fences, light wells, utilities, and easements.

Your hired professional will show no fear when dealing with the 800-pound gorilla known as PG&E for new gas and electric services, and SFPUC. They will know how to avoid being required to upgrade an entire building just because a bureaucrat says it must be done. They will stand their ground when a plan reviewer is wrong. Otherwise, your plans will never be approved and you will have the most over-designed apartment on the planet.

None of this is taught in school.

Design two or more ADUs in a building to lower unit cost.
Building an ADU has certain fixed costs: new water service for the fire sprinkler; enlarged water service to accommodate the ADU; increased amperage to the main electrical service panel; new sewer lines that connect to the city sewer; a fire sprinkler control system and fire department connection; two lighted accessibility egress routes (one is possible but at the expense of putting a fire sprinkler system throughout your entire building); upgraded sidewalks; trees planted in the sidewalk; a Costa-Hawkins agreement and a Notice of Special Restrictions; fixing decay and existing non-complying conditions; providing for site drainage; waterproofing foundations; and constructing a seismic retrofit (usually) to qualify for adding an ADU. Spreading this cost over two or more ADUs reduces the per unit costs of each ADU and increases your return on investment.

More bedrooms will bring the best return on investment.
In the current market, a studio apartment rents for roughly $2,500 per month; a one-bedroom apartment rents for roughly $3,500 per month; and a  two-bedroom apartment rents for roughly $4,500 per month. Three bedrooms vary tremendously, but $5,500 per month rent is achievable. A 500-square-foot space makes a great studio or a small one bedroom. A 700-square-foot space makes a large one bedroom or a small two bedroom. While you personally might recoil at living in such a small space, you will not be living here. You are designing an ADU to rent to someone else who wants to live in the city. In Europe, 300 square feet is suitable for a one-bedroom apartment with a modular living room that doubles as a bedroom at night; a family of four can live in it. These expectations are now part of the renting populace’s mind set.

Interweave the accessible entrance upgrade, alarm upgrade, tenant improvements, and seismic retrofit.
If your building has commercial space on the ground floor, take the opportunity to provide accessible entrances as you design your ADUs. You might be able to share an egress route or re-arrange the commercial space to accommodate the ADU without reducing the actual size of the commercial space. You might be able to align plumbing services for new accessible restrooms in your commercial spaces with the plumbing for the ADU, and you might be able to upgrade the electrical service to your commercial spaces. All older apartment buildings must upgrade their fire alarm systems in the next two years. When you construct an ADU, you must install an alarm system. This new alarm system probably will be incompatible with the old alarm system. Take the opportunity to upgrade now. If you must install a seismic retrofit, design your ADU first. Seismic retrofits have steel columns, shear walls, and reinforced concrete foundations that are difficult and expensive to alter once they are installed. Drilling a sewer line through a three-foot-deep reinforced concrete foundation simply is not possible. Plan ahead.

Schedule new utilities immediately.
Working with PG&E is like working with someone who is facing incarceration and bankruptcy simultaneously. Oh, wait . . . PG&E is facing incarceration and bankruptcy. PG&E has no interest or ability to do anything other than survive at the moment. Getting a new electrical or gas service will take at least a year to 18 months with no problems. As soon as you start your ADU, file an application for a new gas and electrical service.

Attend preliminary design review meetings with all departments.
Once you get a basic design that you believe meets all the constraints, schedule informal meetings with plan checkers in all departments to review your design. Revise your plans to comply with their comments before submitting it for formal approval. The plan checkers appreciate being consulted, and this commits them to your design at a psychological level because they have contributed to it. This will also expedite the formal approval process because you will have made fewer design errors and omissions.

Replace steam boiler systems with a modern alternative.
Steam boilers are expensive to maintain, relocate and replace. Their equipment is bulky and in the way. Old mechanical rooms provide up to 400 square feet of space for an ADU. Their heat is an owner-expense that cannot be passed to the tenants directly, so tenants have no incentive to economize. Take the opportunity to install gas furnaces, mini-splits, or direct-vent furnaces in each unit. These provide better heat and the cost of the utilities will be passed to the tenants. You will recover your cost in roughly seven years.

Plan for fire-proofing secondary egress, gas meter enclosures, trash receptacles, bicycle storage, emergency escape and rescue openings, light and ventilation wells, horizontal exposure, setbacks, and historic preservation.While these issues are not unique to San Francisco, they tend to dominate ADU design considerations because of zero-lot line construction and the difficulty of providing for them in existing buildings. Additionally many buildings have existing non-complying conditions such as insufficient horizontal exposure, insufficient setbacks, and too many stories.

Remember, when you add an ADU at ground level, these issues must be addressed: the building gains a level when evaluating light and ventilation wells; you must have 10-feet of horizontal exposure for the main living space; you cannot build in a setback without a variance; getting a variance is not guaranteed and can take more than a year. If you use a workman’s walkway for primary single means of egress, you will be required to sprinkler your entire building. If you walk through a garage to reach a bedroom window for emergency escape and rescue, you must sprinkler the entire garage. Consider these requirements first, and aesthetic considerations second. Some buildings simply cannot support an ADU economically when you consider the requirements.

Start the design process now,  and wait one to two years to start construction.
Designing and building an ADU is a marathon, not a sprint. The process is as complex as designing a complete building—perhaps even more so because of the complexity of working with an existing building that might be 100 years old. Start now and take your time. Construction costs are at historic levels of insanity in the city. They have been increasing roughly 20% per year for the past five years. Contractors do not negotiate price—they deign to provide a bid if you grovel sufficiently. The design and approval process takes at least one year. You can easily extend a permit another year. By then, I expect sanity will have returned to the market and you will be able to negotiate a reasonable price.

Hire an experienced A-quality contractor and work with your design professional.
Everyone understands price. The less you spend for the same rental income, the greater the return on your investment. Not everyone understands quality or can produce it. However, this affects long-term value, maintenance costs, and rent; furthermore, every contractor claims to be able to construct an ADU for less than their competitors while producing a quality product.

In my 40 years of experience as a design professional, I have learned that there are three basic types of contractors: A, B and C. “A” contractors know how to do every aspect of their job, and they care about completing a job correctly. “B” contractors do not know how to do every aspect of their job, but they do care that their work is done correctly; they can be taught by your design professional; what you save in initial bid price, you will spend in change orders, delays, mistakes, and additional design fees. “C” contractors do not know how to do every aspect of their job and don’t care to learn. I have worked with all three types. The moment I discover I am dealing with a “C” contractor, I run the other direction. No price is low enough to get me to work with them. “B” contractors are suitable for small simple projects in which you can afford to lose your investment with them; for example, a bathroom or kitchen remodel. An ADU is a complex project that should only be attempted by an “A” contractor. You find “A” contractors by referrals, longevity in the market, and prior projects.

“A” contractors also serve as a check on your design professional. They can spot errors and omissions. They know to work with your design professional when such matters arise. They know to ask questions for changed conditions and not proceed otherwise. They do not make design substitutions without asking. They offer improved ways to construct things and costs savings for the owner. They request fewer change orders. They pay their suppliers and subcontractors as required. They account properly and correctly. They document their work. They have adequate on-site management and superintendence. They run clean, safe job sites. They abate hazardous materials and protect neighboring properties. If you need high-end finish work, they can do it. What you pay in increased initial cost you save in mistakes, change orders, legal claims, and professional fees.

Do not be tempted to act as an owner-builder or to not involve your design professional in the construction process because you think you can save money.
You will be responsible if someone gets injured, a neighboring property is damaged, if a subcontractor needs information, if the wrong materials are delivered, if plans are not followed, and if field conditions to not match the plans.

W. Charles Perry is the principal engineer at W. Charles Perry and Associates. He can be reached at 650.638.9546 or