Affordable Housing Regulations

When does the affordable housing requirement apply?

The Inclusionary Affordable Housing Program applies to new residential projects that create housing where none currently exists. This includes:

• Construction of a new home on a vacant lot.
• New subdivisions that create new residential lots or dwelling units.
• New residential development that creates multiple dwelling units.

For applicable projects, 10% of the new dwelling units must be affordable to households earning up to 80% of Area Median Income (AMI), subject to the exemptions and alternative compliance options in SMC Chapter 21.10.

What projects are exempt?

The following are exempt from the program:

• New or reconstructed dwelling units 1,750 square feet or less, including ADUs and cottage housing.
• Multiple new dwelling units with an average floor area of 1,750 square feet or less, including ADUs and cottage housing.
• Units resulting from internal subdivision of existing structures.
• Existing unfinished space conversions to habitable living space.
• Additions or expansions to existing dwelling units.
• Dwelling units being involuntarily reconstructed, including enlargement.
• Bonus units generated from affordability, existing homes, or transit proximity specified in SMC 21.02.050.

What is 80% AMI?

AMI stands for Area Median Income, as most recently determined by the Housing and Urban Development (HUD). Sammamish is part of the Seattle-Bellevue Metro Fair Market Rent (FMR) Area. More information can be found on the HUD User Portal. (SMC 21.04.040.B)

How many affordable housing units are required in new development?

At least 10% of the units in an applicable development must be affordable at 80% AMI. The requirement is calculated by multiplying the total number of housing units by 10%. A unit affordable at 50% AMI counts as two 80% AMI units toward the requirement.

What happens when the calculation results in a fraction?

If the calculation results in a fraction, then the required affordable housing units shall be satisfied either: (a) through payment of a fee-in-lieu, or (b) by constructing a complete affordable housing unit on site. The current affordable housing in-lieu fee is $34.45 per square foot of applicable living space, based on the total floor area of the dwelling unit's finished residential floor area.

Can I do off-site construction or land dedication?

Construction of affordable housing off-site may be allowed if it does not result in an undue concentration of affordable housing in the City. Priority is given to sites within 0.25 miles of the project site, and approval must be prior to the issuance of building permits for the project. The intent is for affordable housing units to be provided before or at the same time as the on-site market rate housing.

Land dedication would be part of a Development Agreement between the applicant and the City. The Development Agreement must be adopted by City Council prior to the issuance of building permits for the project. (SMC 21.10.060)

How long must affordable housing remain affordable?

Affordable ownership units must generally remain affordable for at least 50 years from initial owner occupancy. Rental affordable housing must remain affordable for the life of the project, subject to the provisions of SMC 21.10.

How is “habitable living space” applied in calculating total floor area for purposes of the Inclusionary Affordable Housing Program?

For purposes of administering Chapter 21.10, “habitable living space” refers to the interior floor area of a dwelling unit that is designed and intended for residential living, measured from the exterior walls. This includes rooms and areas used for living, sleeping, eating, cooking, and bathroom facilities, as well as interior spaces integral to and serving the dwelling unit, such as closets, halls, storage areas, utility areas, and similar spaces. Areas not considered part of the dwelling unit’s habitable living space, including garages, unfinished attics, unfinished basements, upper floor vaulted areas, are excluded.

Accordingly, the City will calculate the total floor area based on the finished residential floor area of the dwelling unit, measured from the exterior walls, and will include interior spaces that are integral to the dwelling unit, such as closets, halls, storage areas, utility rooms, and similar spaces.

Example One: Addition to Existing Dwelling Unit

A 1,200 square foot addition is constructed onto an existing 1,300-square-foot home, resulting in a total floor area of 2,500 square feet.

No affordable housing in-lieu fee is required because additions or expansions to existing dwelling units are exempt from the Inclusionary Affordable Housing Program.

Example Two: Existing Residence Remodel and Addition

A 600 square foot addition is proposed to an existing 2,100 square-foot residence. The project also includes a substantial remodel in which 50% of the exterior walls of the existing residence are removed*.

Because more than 50 percent of the exterior walls are removed, the project is considered a reconstruction rather than an addition to the existing residence. The resulting home will have a total floor area of 2,700 square feet.

Under the applicable fee calculation:

• Total floor area: 2,700 square feet
• Exempt floor area: 1,750 square feet
• Fee-eligible floor area: 950 square feet
• In-lieu fee: 950 × $34.45
• Total in-lieu fee: $32,727.50

* Pursuant to SMC 21.04.040.B “demolition” is defined as the removal of more than 50 percent of a structure . For residential buildings, the removal of more than 50 percent of exterior walls.

Example One: New SFR on Vacant Lot Under 1,750 Square Feet

A new single-family home is being constructed on a vacant lot. The total floor area of the home is less than 1,750 square feet.

For purposes of the inclusionary housing calculation:

1 dwelling unit × 10% = 0.1 affordable housing unit

Because the dwelling qualifies for the 1,750-square-foot exemption, no affordable housing designation or payment is required.

Example Two: Voluntary Demolition and Reconstruction of Existing SFR

An existing single-family residence with a total floor area of 2,100 square feet is proposed to be voluntarily demolished and reconstructed on the existing lot. The new single-family residence will have a total floor area of 2,500 square feet. The applicant may satisfy the applicable requirements through one of the permitted compliance options.

Option 1: Affordable Housing Unit

Designate the new home as affordable to a household earning up to 80% AMI, subject to the applicable requirements of SMC Chapter 21.10.

Option 2: Fee-in-Lieu

• Total floor area: 2,500 square feet
• Exempt floor area: 1,750 square feet
• Fee-eligible floor area: 750 square feet
• In-lieu fee: 750 × $34.45
• Total in-lieu fee: $25,837.50

Example Three: Involuntary Construction of a New SFR

An existing single-family home is involuntarily damaged by fire and is reconstructed. The replacement home has a finished residential floor area of 4,000 square feet, which is 800 square feet larger than the original home.

No affordable housing in-lieu fee is required because qualifying involuntary reconstruction and enlargement is exempt from the Inclusionary Affordable Housing Program.

Example One: New SFR with Attached and Detached ADUs

A new single family home and two ADUs are constructed on a vacant lot:

• Primary dwelling (total floor area): 1,750 square feet
• Attached ADU (total floor area): 900 square feet
• Detached ADU (total floor area): 1,000 square feet

Because each dwelling is total floor area 1,750 square feet or less, no affordable housing designation or payment is required.

Example Two: New SFR with Attached ADU

A new single-family home with an ADU is being constructed on a vacant lot:

• Primary dwelling (total floor area): 3,000 square feet
• ADU (total floor area): 1,000 square feet

The 1,000-square-foot ADU is below the 1,750-square-foot exemption threshold and is therefore not subject to the fee calculation.

The primary dwelling is subject to the applicable inclusionary housing requirement:

1 dwelling unit × 10% = 0.1 affordable housing unit

Option 1: Affordable Housing Unit

Designate the primary dwelling as affordable to a household earning up to 80% AMI, subject to the applicable requirements of SMC Chapter 21.10.

Option 2: Fee-in-Lieu

• Total floor area: 3,000 square feet
• Exempt floor area: 1,750 square feet
• Fee-eligible floor area: 1,250 square feet
• In-lieu fee: 1,250 × $34.45
• Total in-lieu fee: $43,062.50

An existing single-family home with a total floor area of 4,500 square feet is internally subdivided into a duplex:

• Dwelling Unit 1: 2,000 square feet
• Dwelling Unit 2: 2,500 square feet

No affordable housing in-lieu fee is required.

An existing single family residence is expanded by converting an existing garage and unfinished storage space into 650 square feet of habitable living area, resulting in a total floor area of 3,000 square feet.

Because qualifying garage conversions and the conversion of existing unfinished storage space into habitable living space are exempt from the program, no affordable housing in-lieu fee is required.

A project proposes 9 new dwelling units.

9 units × 10% = 0.9 affordable housing units

The resulting 0.9-unit requirement may be satisfied through a compliance option permitted under SMC Chapter 21.10.

Option 1: Affordable Housing Unit or Fee-in-Lieu

The applicant may designate a qualifying dwelling unit as affordable at 80% AMI or pay fractional requirement through a fee-in-lieu, if permitted under SMC 21.10.030.

For example, assume the selected unit has a total floor area of 4,000 square feet.

The fee-eligible floor area is:

4,000 − 1,750 = 2,250 square feet

At $34.45 per square foot:

2,250 × $34.45 = $77,512.50

Option 2: Affordable Housing Unit

The applicant may designate a qualifying dwelling unit as affordable to a household earning up to 80% AMI, subject to the requirements of SMC Chapter 21.10.

A project proposes 24 new dwelling units.

24 units × 10% = 2.4 affordable housing units

The project has a requirement for 2.4 affordable housing units.

Option 1: Two Affordable Units and Fee-in-Lieu

The applicant may designate either two qualifying units at 80% AMI or one qualifying unit at 50% AMI and satisfy the remaining fractional requirement through a fee-in-lieu, where permitted under SMC 21.10.030.

For purposes of calculating the fee-in-lieu, the applicant may select any four of the 24 units in the project for purposes of determining the applicable floor area.

The total fee-eligible floor area is 8,850 square feet.

At $34.45 per square foot:

8,850 × $34.45 = $304,882.50

Option 2: Affordable Housing Units

The applicant may use other affordable housing compliance options permitted under SMC Chapter 21.10, including designation of the required affordable units, subject to the applicable affordability requirements.