Listings for a Smithtown home often use "mother daughter" as shorthand for a second kitchen. That label is marketing language. The Town of Smithtown approves the space under a named special-exception use, and the gap between the ad copy and the approval file is what shows up under title before a closing.
What Smithtown issues for a second unit
The Town does not publish a general rental accessory-apartment permit for a one-family house. The path on the Building Department's Applications and Construction Information page is labeled Special Exceptions Requirements, and it points to Temporary Separate Living Quarters for a Family Member alongside the Mother Daughter Renewal form.
Town Code Section 322-82 C(19), Temporary living quarters for parent, sets the terms. The residents of the temporary unit have to be members of the immediate family of the residents of the main dwelling, using the relationships the code itself lists. There may be one such unit per residence. That rule is a zoning condition written into the special exception, not a marketing claim about who belongs in the house.
The Building Department's Special Exceptions Requirements sheet, footer-dated June 12, 2026, lists two signed and notarized applications, a tax bill or "contract of sale" for new owners, three sets of floor plans, two copies of the survey or site plan, a $325 fee, possible Board of Health review, and a Board of Zoning Appeals filing at the Planning Department. Additions or alterations need their own application. The Special Exception Code PDF the Town posts with that packet restates the same living-quarters rules and notes that the three-year permit fee is $325, with additional fees due at Planning for the BZA application. On eCode360, Section 322-81's fee table for one-family residential uses, last amended through Resolution No. 2026-134 dated February 3, 2026, lists the special exception application fee at $1,300.
What this means for a buyer: a second kitchen on a tour is not proof of approval. What matters more is whether a current special exception and a matching Building Department file exist for the space as built.
The covenant that shows up in title
Section 322-82 C(19)(d) says the floor plan has to show that it is economical and practical to convert the use back to a single-family residence, and that the applicant shall file with the deed in the Suffolk County Clerk's office a covenant agreeing to comply with all of the special exception requirements. That covenant is the title item. Before an offer hardens, the title search is where that filing appears next to the deed chain.
The one Smithtown house I sold, a four-bedroom built in 1971 that closed in December 2024, was old enough that a finished second area would already have been through decades of permits and closings. Age alone does not create a living-quarters approval. The covenant and the Building Department file do.
My judgment: treat the covenant language and the current renewal papers as the proof that travels with the house, and treat an unpermitted second kitchen as a single-family house with extra equipment until those papers land.
The three-year renewal, not a permanent right
Section 322-82 C(19)(e) sets an initial three-year period, renewable every three years by the Chief Building Inspector, who inspects to see whether the residents and the physical conditions are the same as approved. When those change, the special exception ends, the separate cooking facilities come out, and access to the main residence is restored.
The Town's Mother Daughter Renewal form is titled Special Exception Use Permit Temporary Separate Living Quarters for a Family Member. It asks for the relationship of the occupant to the owner, the occupant's name, the original approval date, and a notarized owner statement that the facts still match the approval. The form states that the permit will not be renewed until the inspection is approved and the completed form with the fee are submitted. The Building Department requirements sheet dated June 12, 2026 puts the renewal fee at $325 every three years.
The Department of Public Safety investigators' answers page (cat=36, fetched November 9, 2026, answers whether accessory apartments are legal by pointing to a valid mother/daughter permit from the Building Department, renewed every three years. That item carries no separate last-updated stamp on the page, so the date above is the fetch date in early November 2026, when town pages can lag around the November 11 holiday.
What this means at a sale: a seller's current renewal does not hand a finished approval to a buyer. A change of residents is the kind of change the code ties to termination, so a buyer who wants the unit as a separate living area starts from the contract of sale, the BZA path, and a new Building Department file.
Size, conversion, and what the floor plan has to prove
Under Section 322-82 C(19)(b), the temporary dwelling unit may not exceed the greater of 600 square feet or four percent of the lot up to 1,000 square feet. The floor plan has to show a practical path back to a single-family layout. That conversion test is why an inspector can require the second kitchen to come out when the approval ends.
Related reading for older Smithtown houses: Smithtown oil tank rules. Recent sale counts for the town sit on the Smithtown market brief for September 2026.
What it means for a buyer and for a seller
For a buyer, the one check before an offer is whether a current special exception, a deed covenant, and a Building Department renewal file exist for the second unit as shown on the survey and floor plan. Without those, write the contract around a single-family house.
Offer steps: buyers guide.
For a seller, the useful packet is the original BZA approval, the covenant language on the deed, the current Mother Daughter Renewal, and the last inspection date. Describe the space as the Town approved it, not only as it has been used.
Listing steps: sellers guide.
Thinking of selling? Read the Smithtown Seller’s Guide
