What you need to know 

Harwich allows both detached and attached ADUs to be constructed with a special permit from the Zoning Board of Appeals.

Construction Rules

• Only one additional unit can be created on a single family lot.

• The ADU can not be sold separately or owned by a separate entity.

• Only one of the units (primary or ADU) on the property may be rented at any given time.

• The ADU’s net floor area must be 1/2 of the net floor area of the primary home or 900 square feet, whichever is less.

• The ADU must have two bedrooms or less.

• At least one off-street parking space shall be provided for the accessory dwelling unit.

• Minimum lot sizes apply as follows:

  • 15,000 SF in districts RH-1, CV, CH-1, MRL or MRL-1

  • 20,000 SF in districts RL, RM or RR District

  • 40,000 SF in a Water Resource (WR) Overlay District

• The ADU shall be designed so the property continues to look like a single-family property.

• The ADU exterior must match the character of the existing home with matching materials, colors, window styles and roof design.

• An addition or detached ADU must not exceed the site coverage for the zoning district.

• Setbacks will follow the zoning district’s rules for new construction.

See the full text here: Zoning Ordinance Article 10, Section H: Single-family dwelling with accessory apartment