Smithtown is one of those Long Island towns where space is the main attraction. Colonials and updated capes sit on large, leafy lots, driveways hold several cars and a finished basement is as likely to be a family room as a utility space. People who buy here usually want room to spread out, and many are now using that room to host aging parents, adult children or long-term guests. That has turned the in-law suite into one of the most common reasons a Smithtown homeowner starts a serious renovation.
This page is for Smithtown owners who want a high-finish, full-scope interior project: a colonial gutted and rebuilt, a lower level turned into a true apartment, or a main floor opened and refinished from front to back. We cover what the housing and lot sizes allow, how town permits work, how to vet contractors, and how 2026 costs look. Smithtown is a far-service area for us, and we explain what that means for scheduling.
Not every Smithtown renovation is the same, but several themes recur.
An in-law suite is where luxury and practicality meet. The space has to be comfortable, safe and accessible: wide doorways, a curbless shower, good lighting, non-slip tile, reachable storage and a plan for emergency egress. Those details are not extras; they decide whether the room works for the person who will use it.
Before you spend a dollar on finishes, find out what the town allows. Rules about accessory apartments differ across Long Island municipalities, and some restrict or prohibit separate dwelling units in single-family zones. A separate kitchen is often the line that changes the answer.
Septic capacity deserves emphasis. Many Suffolk parcels rely on on-site wastewater systems, and adding bathrooms or bedrooms can trigger review. Ask early, because undersized systems turn into expensive surprises.
If the answer is that a separate unit is not allowed, a family-use suite without a full kitchen can sometimes accomplish the same goals. A design professional can help you tell the difference between what is permitted and what is merely common. For the general logic of permits, our Do I Need a Permit? guide, written for New York City, is a helpful starting framework.
For a project of this size, the quality of the paperwork is as important as the quality of the tile. Suffolk County regulates home improvement contractors through its consumer affairs office, and the county's Suffolk County website is where you can begin checking credentials. Our explainer on the NYC Home Improvement Contractor license describes the New York City version, which does not govern Smithtown projects, but the questions it raises apply anywhere: who issued the license, what does it cover and how do you confirm it?
The second document is the certificate of insurance. It should show general liability and workers' compensation coverage, with dates and limits that are current. Our guide to the certificate of insurance for renovations explains each line.
N.Y. Renovation Services is a licensed and insured, in-house design-and-build company. We prepare drawings and permit paperwork, run demolition, tile, flooring, millwork and painting under one contract and coordinate licensed electrical and plumbing trades. Our estimates are itemized and our contracts are detailed, with no hidden fees.
For a project that adds a bedroom, a bath and a kitchenette in a lower level, the stakes are high: moisture control, egress, fire safety and the legality of the finished unit all have to come together. A handyman who can hang cabinets cannot answer those questions. A design-build team that handles the paperwork can.
We also donate 5% of total project cost to a nonprofit of your choice.
Our regular Long Island service area covers Nassau County and western Suffolk, and Smithtown lies at the far edge of what we can serve efficiently. We take larger projects here by arrangement. In practice, that means a few things.
Large lots help. Driveways, side yards and garages give crews room to stage materials, run a dumpster and keep the site organized, which offsets some of the travel logistics. Ask us on the first call whether your project fits, and we will give you a straight answer.
All figures are typical 2026 planning ranges for the New York metro, not quotes. Access, hazardous materials, finishes, scope and travel logistics move prices, and a written, itemized quote governs.
| Item | Typical 2026 planning range |
|---|---|
| Cosmetic refresh | $100-$250 per sq ft |
| Mid renovation with kitchen and bath | $200-$400 per sq ft |
| Full gut renovation | $250-$500+ per sq ft |
| High-end or structural | $500-$1,000 per sq ft |
| Design, engineering and permits | Often +15-25% |
| Bathroom renovation | $30,000-$60,000+ |
| Kitchen renovation | $25,000-$85,000+ |
| Interior demolition | $8-$30 per sq ft |
| Hardwood installed | $12-$28 per sq ft |
A 900 square foot basement suite built at mid-renovation rates of $200-$400 per square foot lands between about $180,000 and $360,000, before design and permit fees. The wide gap reflects choices such as a full kitchen versus a kitchenette, a custom bath versus a standard one and whether new egress windows, waterproofing and drainage are needed. Treat those numbers as arithmetic, not a quote for any home.
For room-by-room detail, see the 2026 NYC renovation cost guide and our kitchen and bath remodels in Smithtown page.
Basements are the most common place to put an in-law suite in Smithtown, and the most unforgiving. A good plan covers the following.
Our premium flooring in Smithtown page covers substrates and moisture testing. If the lower level is an older space, also test suspect floor tile and mastic before demolition, because the EPA notes that asbestos can appear in materials of that vintage.
Above the suite, the main living areas are where a colonial earns its keep. Typical moves include:
Sequence is everything. Structure and rough-ins come first, then insulation and drywall, then tile and floors, with millwork and paint last. If you try to paint before floors are sanded, you will repaint. If you install floors before heavy trades finish, you will refinish. Our interior painting services in Smithtown page explains the final stage, including skim coating at roughly $2-$5 per square foot where smooth walls are wanted, and our co-op and condo gut renovations in Smithtown page covers unit-level projects if you own a townhouse or condo.
A word on kitchens in large colonials: scale changes the layout rules. In a big room, an island that looks generous on paper can end up isolated from the cooking zone, so the working triangle between sink, range and refrigerator should stay compact even when the room is not. Plan lighting in layers, with recessed fixtures for general light, under-cabinet lighting for tasks and pendants for atmosphere, and put every layer on its own switch or dimmer. Appliance choices drive ventilation and electrical needs, and a powerful range hood requires make-up air in a tight house, which the mechanical designer should address before cabinets are ordered.
Smithtown has long-established village centers and older homes. Some may sit in locally designated historic areas, and the town can tell you whether yours does. The New York City Landmarks Preservation Commission, by contrast, covers only buildings in the five boroughs. Our guide on LPC permits in historic districts explains the city process, and it is a helpful reference if you own property in both places.
For a Smithtown home, ask whether any historic designation or local review applies, particularly for exterior changes such as window replacement, additions or porch work. Interior-only renovations typically face fewer restrictions, though rules vary by parcel.
A realistic timeline for a full Smithtown interior project has five stages.
Four to nine months is typical overall. Because Smithtown is by arrangement, we schedule visits and crew mobilization together and tell you in advance when a delivery or inspection puts the calendar at risk.
Our guide to how to compare renovation bids can help you line up proposals from any contractor on equal terms. If you want to see our scope and numbers next to others', ask us for an itemized quote.
We take renovation projects in the Smithtown area by arrangement.
The Town of Smithtown is known for colonials on large lots, village centers and a quiet, suburban feel. Septic capacity, zoning for accessory apartments and the economics of travel shape how projects here are planned. For comparison, Garden City has a stricter village process, Hempstead has denser multifamily housing and Long Beach is a barrier-island flood setting. The Long Island renovation services hub brings them together.
Begin with a call, a few photos and a description of the rooms involved. We will tell you whether the project fits our by-arrangement service for Smithtown, outline scope and ranges, and schedule a site visit to produce a written, itemized quote.
Helpful to have ready:
There is no charge for the estimate. When you are ready, request your free renovation quote and we will respond with next steps.