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Residential Infill Options

Guide
The residential infill options result in multiple units on one lot. One or all the units may be rented. Some residential infill options also allow for the land to be divided through a Middle Housing Land Division, so the units can be bought and sold separately.
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Single dwelling zones offer flexibility in the number of units allowed and how they are configured. The amount of floor area allowed on a lot is limited to ensure infill development is more compatible with existing development. The amount of floor area allowed generally increases as units are added to a lot.

The residential infill options result in multiple units on one lot. One or all the units may be rented. Some residential infill options also allow for the land to be divided through a Middle Housing Land Division, so the units can be bought and sold separately.

What configurations are allowed?

House (one dwelling unit)

Detached single-dwelling or manufactured homes are allowed on their own on most single dwelling zoned lots.

  • Exception: A minimum of two units are required when sites exceed specified lot sizes: R7 – larger than 14,000 square feet, R5 – larger than 10,000 square feet, R2.5 – larger than 5,000 square feet.

House with one Accessory Dwelling Unit (ADU) (two dwelling units)

Houses, manufactured homes and attached houses are allowed with one ADU. An ADU is a secondary unit on the same lot as the house. It contains its own kitchen, bathroom and sleeping area. It can be located within a house or it may be in a detached structure. Sometimes existing detached structures can be converted into ADUs.

  • Minimum lot size standards apply for ADUs proposed with attached houses: R20 – 10,000 square feet, R10 – 5,000 square feet, R7 – 3,500 square feet, R5 – 2,500 square feet, R2.5 – 1,500 square feet. No minimum lots sizes apply for lots with houses or manufactured homes.
  • Additional FAR is earned for two dwelling units.
  • If the ADU is detached or connected to the house with a breezeway, additional development standards in 33.110.245 apply. These ADUs must also be located 40 feet from a front lot line or located behind the house (see 33.205.040.C.3).
  • ADUs are limited to 800 square feet in living area (or 75 percent of the living area of the primary structure, whichever is less), unless they are added to the basement of a house that has been on the site for at least 5 years.
  • Middle Housing Land Divisions are not allowed on sites with ADUs.

House with two ADUs (three dwelling units)

Two ADUs are allowed on lots with houses, attached houses and manufactured homes. One ADU may be part of the house and one may be detached. There may also be a house and two detached ADUs. Two ADUs inside or attached to a house are not allowed. It is possible for the two detached ADUs to be attached to each other – either side-by-side or stacked.

  • Minimum lot size standards apply: R20 – 12,000 square feet, R10 – 6,000 square feet. R7 – 4,200 square feet, R5 – 3,000 square feet and R2.5 – 1,500 square feet.
  • Additional FAR is earned for three or more units.
  • Property must be located on a city-maintained street and not within the “z” overlay zone.
  • If an ADU is detached or connected to the house with a breezeway, additional development standards in 33.110.245 apply. These ADUs must also be located 40 feet from a front lot line or located behind the house (see 33.205.040.C.3).
  • ADUs are limited to 800 square feet in living area (or 75 percent of the living area of the primary structure, whichever is less), unless they are added to the basement of a house that has been on the site for at least 5 years.
  • One of the units on the site must meet the visitability standards.
  • Middle Housing Land Divisions are not allowed on sites with ADUs.

Duplex (two dwelling units)

A duplex is a single structure that contains two dwelling units located on its own lot. The units might be arranged side-by-side or they may be stacked on two or more levels.

  • Additional FAR is earned for two dwelling units.
  • “Detached Duplex” development is allowed that consists of two detached primary dwellings. The lot must have a primary dwelling unit that has been on the site for at least 5 years. The maximum height for the new dwelling unit is 25 feet. Detached Duplexes are not allowed on sites located in the “z” overlay zone.
  • Middle Housing Land Divisions are allowed for sites with Duplexes and Detached Duplexes. Duplexes that are not detached must be proposed as side-by-side meeting the townhouse building code.

Duplex and ADU (three dwelling units)

A detached ADU may be proposed on a lot with a duplex.

  • Minimum lot size standards apply: R20 – 12,000 square feet, R10 – 6,000 square feet. R7 – 4,200 square feet, R5 – 3,000 square feet and R2.5 – 1,500 square feet.
  • Additional FAR is earned for three or more units.
  • Property must be located on a city-maintained street and not within the “z” overlay zone.
  • Development standards in 33.110.245 apply for detached ADUs. They must also be located 40 feet from a front lot line or located behind the duplex (see 33.205.040.C.3).
  • ADUs are limited to 800 square feet in living area (or 75 percent of the living area of the larger unit in the duplex, whichever is less).
  • One of the units on the site must meet the visitability standards.
  • Middle Housing Land Divisions are not allowed on sites with ADUs.

Triplex and Fourplex (three or four dwelling units)

A triplex is a single structure that contains three dwelling units located on one lot. A fourplex is a single structure that contains four dwelling units located one lot. The units might be arranged side-by-side or they may be stacked on two or more levels.

  • Minimum lot size standards apply: R20 – 12,000 square feet, R10 – 6,000 square feet, R7 – 4,200 square feet, R5 – 3,000 square feet and R2.5 – 1,500 square feet.
  • Additional FAR is earned for three or more units.
  • Property must be located on a city-maintained street and not within the “z” overlay zone.
  • One of the units on the site must meet the visitability standards.
  • Middle Housing Land Divisions are allowed for sites with triplexes or fourplexes. Development must be proposed as side-by-side meeting the townhouse building code.

Affordable fourplexes and multi-dwelling structures (four to six dwelling units)

Structures are also allowed with four to six units in one building on one lot. The units might be arranged side-by-side or they may be stacked on two or more levels.

  • Minimum lot size standards apply: R20 – 12,000 square feet, R10 – 6,000 square feet, R7 – 4,200 square feet, R5 – 3,000 square feet and R2.5 – 1,500 square feet.
  • Property must be located on a city-maintained street and not within the “z” overlay zone.
  • 50 percent of the total number of dwelling units on the site must be affordable to those earning no more than 60 percent of the area median family income or an affordability level established by the Title 30 Affordable Housing code.
  • Maximum FAR is 1.2:1 and maximum height is 35 feet.
  • At least two units must meet the visitability standards.
  • Middle Housing Land Divisions are allowed for sites with fourplexes only. Development must be proposed as side-by-side meeting the townhouse building code.

Cottage Clusters (three to sixteen dwelling units)

Cottage clusters are between three and 16 individual detached dwelling units on one lot.

  • Cottage clusters are not allowed in the R20 zone. Minimum lot size standards apply in other zones: R10 and R7 – 7,000 square feet, R5 and R2.5 – 5,000 square feet. Cottage cluster sites must not be greater than one acre.
  • A minimum number of units is required based on the site size: R10 – 1 unit per 12,500 square feet, R7 – 1 unit per 8,750 square feet, R5 – 1 unit per 6,250 square feet, R2.5 – 1 unit per 3,125 square feet.
  • Property must be located on a city-maintained street and not within the “z” overlay zone.
  • No ADUs are allowed with cottage cluster development.
  • Floor area limits in base zone do not apply. Additional development standards for cottage clusters are listed in 33.100.265.G.
  • Common outdoor areas are required for cottage cluster development. Not allowed: The common outdoor areas may not include projections from individual units, such as eaves, bay windows, and patios.
  • At least 33 percent of the units must meet the visitability standards.
  • Middle Housing Land Divisions are allowed for cottage cluster development.

Other requirements to consider:

  • Building codes may differ for detached one or two dwelling units and structures with three or more units, depending on how the units are constructed. This can greatly impact the cost of the project.
  • When a Middle Housing Land Division is proposed, dwelling units must be detached or side-by-side meeting the townhouse building code.
  • System Development Charges (SDCs) are currently waived for ADUs on sites that are not used as Accessory Short-term Rentals. Adding dwelling units that are not ADUs may trigger SDCs.
  • Adding dwelling units may require upgrading infrastructure (water, sewer, stormwater, street improvements, or street trees) as part of the permit process.

Contact

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