Accessory Dwelling Units

In the past few months, we have started receiving many calls for new or converted Accessory Dwelling Units, or ADU’s. More and more homeowners want a separate apartment on their property where guests can stay, where an aging parent can live independently, and – in a few cases – where the family can live comfortably while we remodel their main house!

New Guidelines for Accessory Dwelling Units

In response to California’s housing shortage, recently adopted legislation promotes the development of Accessory Dwelling Units, or ADU’s. Going into effect January 1, 2018, these new laws have eased many of the requirements associated with building a secondary dwelling unit that can be used as a guesthouse or for rental income. 

ADU’s are self-contained apartments that include a full kitchen. The unit can be attached to the main house, or it can be a detached structure. Unlike a Detached Accessory Structure (described in my earlier blog about Guesthouses) an ADU may be used for sleeping, and it may be rented out. Only one ADU is permitted on any one lot. 

Where can an ADU be located on the property, and how big can it be?  

Many other websites indicate that a residential lot must be at least 5200 square feet before an ADU is allowed, but this is not true in the city of Sacramento. Here, any size lot may have an ADU. 

There is, however, a limitation on lot coverage, so a smaller lot may have limited space for an ADU. If the property is zoned R-1, then the maximum lot coverage is 40% or 2500 sq. ft., whichever is greater, but in no case can lot coverage exceed 50%. All structures on the property count towards lot coverage, including sheds and covered patios. 

If the ADU is attached to the main house, it cannot exceed 50% of the floor area of the main house. For example, if your house is 1500 sq. ft., than an attached ADU cannot be more than 750 sq. ft. The maximum floor area of any ADU is 1200 sq. ft. 

If the ADU is a detached building, it can be up to 1200 sq. ft. regardless of the size of the main house. And if part of the detached building is a garage, then the area of the garage does not count towards the 1200 sq. ft. limit.

If the ADU is new construction, it must meet all the same design guidelines that are required for the main house. So, for example, the new structure must have the required setback on the side, usually five feet. But if an existing building, such as a garage, is being converted, then no setbacks are required; like so many garages in Sacramento, the building can be right on the side yard or rear yard property line. Any addition to the existing structure, however, would need to meet setback requirements. And always remember to check for utility easements, as described in the blog about Guesthouses. 

Two-Story Accessory Dwelling Units

 Under the guidelines for Detached Accessory Structures, one of the greatest obstacles to converting a garage into living space was the height limitation. The Guesthouse blog describes the 18-foot height limitation that makes two story structures very difficult to design. The new guidelines allow ADU’s to be 35 feet tall, although it would be unusual to need more than 25 feet for a two story building on a slab. 

When a secondary dwelling unit is built above an accessory structure, it must maintain a five foot rear yard setback and, in zone R-1, a five foot side yard setback. 


 The new legislation for secondary dwelling units took away the requirement for additional parking. One off-street parking space is required for the main house, but no additional parking is needed for the ADU. If an existing garage is being converted, then an alternate off-street site must be provided that is at least 10 feet wide and 20 feet long. 




Now that the 2016 Energy Code has gone into effect in California, this is a good time to review the new lighting requirements, as well as your lighting options.

Changes to the Code

 The revised code reduces energy usage throughout the home, but it also provides a much more straightforward set of guidelines. The earlier code, issued in 2013, was rather complicated, with different rules for different rooms of the house. For example, we had to use a formula to determine how many incandescent fixtures could be installed in a kitchen. To meet the code, we would install ugly fluorescent fixtures over a beautiful new kitchen island, and then, after final inspection, the owners would change out those fixtures for the incandescent pendant lights they really wanted in the first place.

Now, all permanently installed fixtures in a home must be high-efficacy, the reality being that all light sources will have to be fluorescent or LED. But that doesn’t mean you have to buy fluorescent or LED fixtures. You CAN use fixtures that take screw-base bulbs, as long as you use high efficacy bulbs that are labeled JA8-2016. The one place we can no longer use screw-in bulbs is recessed lighting; all recessed cans must be high-efficacy fixtures.

Another important new change to the code is that all fixtures must be controlled by a dimmer switch, or, alternatively, they must have a switch that turns the fixture off when the room is vacant; these switches are called “manual-on/automatic-off vacancy sensors.” The only exceptions to this rule are hallway and closet lights, which do not require either a dimmer or a vacancy sensor switch.

The code gets a little stricter for bathrooms, laundry rooms, utility rooms, and garages. In each of these spaces, at least one fixture must be controlled by a vacancy sensor switch. Presumably, people are more likely to use these rooms briefly and then wander away without switching off the lights.

Exterior lighting is also under stricter regulation. Outdoor lights must have a photocell and a motion sensor, or a photocell and astronomical time switch for dusk to dawn lighting.

Light Sources

For residential lighting, we typically use three types of bulbs—which, by the way, are correctly called “lamps.” Today’s residential light fixtures use incandescent, fluorescent, and LED lamps.

Incandescent lamps are becoming a thing of the past, although some diehards still have hidden stashes in their basements. These lights use a lot of energy, and they create a substantial amount of heat. But we love the warm color they produce, and the ambiance provided by dimming.

Fluorescent lamps are much more energy efficient, but they have many drawbacks. They can flicker, they’re slow to warm up to their full brightness, and most of them can’t be dimmed. The industry claims that CFLs will last for ten years, but the reality is they only last for a year or two because turning them off and on drastically shortens their lifespan.

LED lamps more energy efficient than CFLs, they’re dimmable, and they have good color rendering. The bulbs are more expensive than CFLs, but cost has dropped to a point where this is no longer an excuse for not buying them.

Watts and Lumens

 Watts are a measure how much energy is being used. Lumens are a measure of how much light is being produced. Knowing how many lumens per watt a lamp produces tells us the efficacy of the lamp.

A brand new 60-watt incandescent bulb produces about 800 lumens of light. As the bulb ages, it will produce less light, but it will keep using 60 watts of energy. A halogen bulb, which is a more efficient type of incandescent bulb, will produce 800 lumens using about 43 watts.

That same amount of illuminance, 800 lumens, will be produced by a 13-watt CFL or a 10-watt LED lamp. The energy savings are significant.

Color Temperature and CRI

 The color temperature of light is measured in degrees Kelvin. Confusingly, the higher the temperature, the cooler the color appears. Candlelight has a color of about 2000K, while daylight is 5000K or higher.

Incandescent light has a temperature of 2700K, which appears as a yellowish, warm color. As these bulbs age, they not only produce fewer lumens, they also glow at a warmer color. Dimming incandescent lights produces the same effect—as they dim, the color temperature shifts lower and the color becomes warmer.

Today, both fluorescent and LED bulbs are available in many color temperatures. Look for 2700K if you want to mimic incandescent light. Often, boxes of bulbs will be labeled “warm white” or “soft white,” but close examination will show that the bulbs’ color is 3000K.  This may not be what you want. And remember, as the Kelvin temperature increases, the color of the light will be cooler.

There is one more measurement of a light source—the CRI, or Color Rendering Index. This number tells us how accurate a light source is at rendering color. The higher the CRI, the better its color rendering ability. A CRI of 90 or higher is excellent, and this is the standard that is now required for residential lighting in the new Energy Code. 




A lot of homeowners in Land Park and Curtis Park ask us about converting their detached garages into guesthouses or studios. The first question on their minds is: How much will it cost? But there are some other questions they might need to consider first.   

Accessory structure vs. secondary dwelling unit

    In Sacramento’s older neighborhoods, most of the existing detached garages are classified as accessory structures. An accessory structure may be converted to living space, but, unlike secondary dwelling units, it cannot legally be used as sleeping quarters. Instead, it might become an office, art studio, gym, or space for some other type of waking pursuit.  

    On the other hand, a secondary dwelling unit might sound more desirable, because you can legally use it as a guesthouse or even rent it out. Keep in mind, however, that this type of structure will need to meet all applicable building codes for a residence. One of those codes – the one that prevents most homeowners from choosing this option – is that the building must be at least five feet from the side yard property line. Where lots are typically 50 feet wide, that extra five feet on the side of the new structure is too much of a sacrifice. And don’t forget the extra costs you’ll be facing to provide separate utility services to your guesthouse. It might be cheaper to put up Aunt Betty at the Westin. 

    Given costs and restrictions, our clients almost invariably choose to build accessory structures, not secondary dwellings. We know several very happy artists and home-based business people, but also some who are using their new space for activities beyond our control. We just ask that you wait to bring in any compromising evidence until we’ve moved on to the next job. 

Parking regulations

    If you’re tearing down your old garage, you must be certain that you’re still meeting off-street parking requirements. A single family home must have at least one parking space. That space doesn’t have to be covered, but it has to be at least ten feet wide and 20 feet long, and it can’t be in your front yard setback. If you won’t have dedicated garage space, the area in front of your new building might satisfy the parking requirement. 

Where can it be built, and how big can it be? 

    As long as it’s at least 60 feet from the front property line, your accessory structure can be built right on the side yard and rear yard property lines, but there are a few caveats. 

    First, check with the city or search through your title documents to find out whether there are utility easements crossing your property. It’s very common in Land Park, Curtis Park, and East Sac to have a five or six foot easement across the back of the property for electric (above) and sewer and gas (underground.) You cannot build within any easement, even if the old building slated for demolition was in that area.

    The location of the building might also be affected by limitations on lot coverage. Assuming your house is in R1 or R2 zoning, you can cover up to one-third or 350 square feet of your rear yard setback, which is defined as the back 15 feet of the property. Total lot coverage, including the main house and covered patios, cannot exceed 40 percent. 

    If you're thinking about a two-story accessory structure, the greatest design challenge will be the height restriction. The building may not be more than 18 feet to the highest point of the roof. You can add dormers to increase headroom in the second story, but the combined width of the dormers on any one side of the building can’t be more than one-fourth of the width of the wall on that side. So, for example, if your new building will be 24 feet long, it can have a six-foot wide dormer on each side. 

     If your home is on a corner lot or if your garage faces an alley, there are some different regulations that apply. Other considerations for every project include firewalls and our favorite, the “building envelope,” but let’s save those topics for future articles. 

Breaking the rules

    If your design doesn’t meet all these requirements, we can apply for a Planning Entitlement. Depending on the specifics of your project, the application will be reviewed at staff level, director level, or commission level, each with its own marvelous fee schedule and timeline.