Building an ADU in North Hempstead, NY: Village Zoning, Permits & Costs

The Town of North Hempstead runs along Nassau County's north shore, from the Queens line out to the Suffolk border, taking in Great Neck, Port Washington, Manhasset, Roslyn, New Hyde Park and Westbury. Property values here are among the highest in the county, and lot sizes vary enormously — from tight village parcels to substantial north shore estates.

That combination makes accessory dwelling units attractive and complicated in roughly equal measure. High land values mean an ADU adds serious equity. Dense village governance means the rules change from street to street. This guide covers both.

North Hempstead Is Mostly Villages — Check Yours First

North Hempstead contains one of the highest concentrations of incorporated villages in New York State. Great Neck alone is a cluster of separate villages, each with its own government. Add Port Washington North, Manorhaven, Roslyn, Roslyn Harbor, Flower Hill, Munsey Park, Plandome, Sands Point, Williston Park, Mineola, New Hyde Park, East Hills and many more.

Every one of those villages has its own zoning code and building department. Town of North Hempstead accessory dwelling rules do not apply inside them. Two houses a few hundred feet apart can sit under completely different regimes.

Unincorporated areas — including much of Port Washington, Manhasset, Albertson, Carle Place, Greenvale and New Cassel — fall under the Town.

Do not start a design until you have confirmed which authority reviews it. This is the most common and most expensive early mistake in North Hempstead.

Accessory Apartment Rules

Where the Town of North Hempstead has jurisdiction, accessory dwellings are permitted under defined conditions rather than by right. Expect requirements along the familiar Long Island lines: owner-occupancy of one unit, a single accessory unit per lot, size limits relative to the principal dwelling, minimum lot area, setback and lot coverage compliance, off-street parking, independent egress, and a renewable rental permit or registration.

Villages within the town often impose stricter standards than the town itself, and some are far more restrictive about rental use generally. Because both town and village codes are amended over time, verify the current standard with the specific authority before designing. We confirm this at the start of every project.

North Shore Site Conditions

The north shore's topography is genuinely different from the south shore's, and it affects ADU work. Sloped and terraced lots are common, which can make a walkout lower-level unit unusually attractive — natural grade often delivers the light and egress that a flat-lot basement struggles to achieve.

Slope also means retaining walls, drainage design and more involved foundation work on detached structures. Mature tree cover is another factor: many north shore parcels have significant specimen trees, and both town and village codes commonly regulate their removal.

Sewer service varies across the town. Where a property is on septic, additional bedrooms trigger county health department review, exactly as they do in Suffolk.

Plus One ADU Program

New York State's Plus One ADU Program offers up to $125,000 per project to help eligible homeowners create or rehabilitate an accessory dwelling unit, administered by New York State Homes and Community Renewal through regional partners, targeting low-to-moderate income owner-occupants.

Income limits and availability vary by partner and funding round. Given north shore property values, some homeowners here will fall outside the income eligibility — confirm before planning around it.

ADU Types That Work in North Hempstead

Walkout lower level. The sloped lots common here make this format work better than a standard basement conversion, with real windows and a legal grade-level exit.

Attached addition. Predictable and code-friendly where lot coverage allows.

Above-garage unit. Adds a unit without additional ground coverage — useful where lot coverage limits are the binding constraint.

Detached cottage. Viable on larger north shore parcels, subject to setbacks, coverage and tree regulations.

What ADUs Cost in North Hempstead

Typical ranges for permitted work. North shore finish expectations tend to run higher than the county average, which pushes the top of each range:

Walkout lower-level unit: roughly $90,000 to $170,000.

Above-garage unit: roughly $130,000 to $230,000.

Attached addition: roughly $170,000 to $290,000.

Detached cottage: roughly $220,000 to $350,000.

Where septic upgrades or significant site work are required, add to these figures.

Where We Build

We are a Suffolk County licensed general contractor. This guide is published as a reference for Town of North Hempstead homeowners researching accessory dwelling units; for construction work we serve Suffolk County, including Huntington, Smithtown, Brookhaven, Islip and the East End.

Frequently Asked Questions

My village has stricter rules than the town. Which applies?

The village's. If your property sits inside an incorporated village, that village's zoning code and building department govern the project, and town rules do not apply.

Is a walkout basement easier to approve than a standard basement?

Often, yes. Natural grade tends to deliver compliant light, ventilation and a legal grade-level second means of egress without excavating a window well.

Do I need health department approval?

If your property is on septic rather than sewer, adding bedrooms generally triggers county health department review. Sewer service varies across the town.

How long does approval take?

Expect a few months for approvals in unincorporated areas, and potentially longer in villages with additional architectural or design review, followed by three to six months of construction.

Related ADU Guides

• Nassau County ADU overview
• ADUs in Cold Spring Harbor
• ADUs in Northport
• Plus One ADU grant program
• ADU permits on Long Island