Accessory dwelling unit under construction on a Long Island lot

Alec's Construction builds and legalizes accessory dwelling units in Holbrook, Suffolk County — basement and lower-level apartments, garage conversions, dormered second floors and additions — working out of the yard in East Patchogue. Most of what people call an ADU here is an apartment inside the house they already own, and a lot of those already exist and need to be made legal. That is winter work.

Accessory Apartments in Holbrook

Holbrook sits on the Brookhaven–Islip town line, and the two towns run different accessory apartment programs with different owner-occupancy rules, different renewal cycles and different application forms. The housing — 1960s to 1980s ranches and colonials with full basements and two-car garages — gives you two candidate spaces on most lots, and which one makes the better apartment depends on egress and ceiling height more than anything else.

The Split-Level Lower Level Is Already Half an Apartment

A split or a hi-ranch was built with a lower level at grade, its own exterior door, full-height ceilings and daylight — which is why so many of them already function as informal apartments. Legalizing one is mostly a matter of what the code asks a dwelling unit to have and the builder never bothered with: a compliant egress opening in the sleeping room, interconnected smoke and carbon-monoxide detection between the units, a fire separation at the shared floor and stair, and the kitchen and bath plumbing and electrical inspected.

The corrections are usually smaller than owners fear. The part that takes the time is the paperwork — the accessory apartment permit, the owner-occupancy affidavit, the inspections — and that is precisely why the winter is the right season for it.

What the Town Asks a Dwelling Unit to Have

  • A compliant egress opening in every sleeping room — net clear opening, sill height and well where it is below grade
  • Ceiling height that meets the habitable-space minimum, measured under the beams and ducts, not between them
  • A fire separation between the apartment and the main house at the shared floor, wall and stair
  • Smoke and carbon-monoxide detection in both units, interconnected
  • A kitchen and a full bath, with the plumbing and electrical inspected
  • Its own exit to the outside
  • The owner living in the house, and the accessory apartment permit with its renewal cycle
Framed and insulated Long Island basement wall going up in winter

Permits in Holbrook

Holbrook straddles the Brookhaven and Islip town line and both are possible, so the department is confirmed by address before anything is filed. The accessory apartment permit sits on top of the building permit — two processes, one address — and the rules differ by town and by village. We confirm which authority governs from the tax map, then read the current rules for that authority, then walk the house against them. It saves months.

The Winter Plan

The interior legalizations run straight through the winter, because none of the work depends on the weather. For a new build — a dormer, an addition, a detached unit — the winter is when the survey, the drawings and the permit application get done so the framing can start as soon as the ground allows.

Free walkthrough in Holbrook. Alex walks the space against the code, lists what passes and what does not, and you get the list and the photographs whether or not you hire us.

Frequently Asked Questions

My Holbrook house could be Brookhaven or Islip. Does that change the ADU?

It changes the process, the paperwork and some of the rules, so it is the first thing we settle. Both towns permit accessory apartments in owner-occupied houses, but they are two different programs. We confirm the town by address, then look at the basement and the garage against that town's requirements for egress, ceiling height and separate access. The building work is similar either way; the permit path is not.

Do I have to live in the house to have an accessory apartment?

In every Suffolk town we work in, yes — the accessory apartment permits are written around owner-occupied houses, and the owner signs an affidavit to that effect. The permits also typically renew on a cycle rather than lasting forever. The specific rules differ by town and by village, and we confirm them for the actual address rather than generalise.

What does an ADU need that a finished basement does not?

A compliant egress opening in every sleeping room, a fire separation between the unit and the main house, interconnected smoke and CO detection in both units, a kitchen and a bath that pass inspection, ceiling height that meets the code for habitable space, and its own means of exit. A finished basement family room is held to a lower standard on most of those. The gap is what a legalization closes.

What is the difference between legalizing an apartment and building one?

Legalizing means the space already exists and functions as an apartment — a finished basement, a lower level, a converted garage — and the work is bringing it up to what the town requires for a dwelling unit and getting the accessory apartment permit. Building one means creating the space. Legalization is almost always interior work and it is what we schedule through the winter.

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Work With Alec's Construction

This guide is written by the crew that does the work. See Alec's ADUs service — accessory apartments, garage conversions and grant paperwork. Licensed and insured on Long Island, one crew start to finish, free walkthrough and a written estimate inside 48 hours.

Booking the cold months now: we also handle Additions & New Construction and Bathroom Remodeling.

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