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Rhode Island ADU Contractor

Rhode Island ADU Contractor: Accessory Dwelling Units

We design and build ADUs across Rhode Island, including in-law suites, garage conversions, backyard cottages, and carriage house conversions. One team managing your project from permits to final walkthrough.

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Toensing Construction is an ADU builder and contractor for Rhode Island homeowners. We build accessory dwelling units of every type, including in-law suites, garage conversions, and backyard cottages, under Rhode Island's ADU law as updated in 2024. As a carpenter-led company based in Warren, RI, owner Colby Toensing manages the full process personally, from permitting through final trim work, rather than handing it off to subcontractors.

Rhode Island ADUs

More Space. More Options. More Value.

Rhode Island's ADU (accessory dwelling unit) law, updated by the General Assembly in June 2024 as part of a broader push to expand housing, made it easier for homeowners to add a second living unit to their property. Whether you want space for aging parents, adult children, long-term rental income, or a dedicated guest suite, an ADU can be a smart, long-term investment. Toensing Construction builds ADUs across the state, from Warren, Bristol, and Barrington to Cranston, East Greenwich, North Kingstown, South Kingstown, and Narragansett.

Not sure what Rhode Island's ADU rules allow on your property, or what an ADU costs? Our Rhode Island ADU rules guide and ADU cost and timeline guide cover both.

Toensing Construction handles the full ADU process, from early design conversations and permit navigation with your local planning department through construction and final inspections. We have experience working with Rhode Island's zoning requirements, including size limits like the state law's by-right allowance for an ADU on residential lots of 20,000 square feet or more (R.I. Gen. Laws § 45-24-73), and can help you understand what is feasible on your specific property, whether it's a suite for a family member or a stand-alone rental unit.

Every ADU project starts with an honest conversation about what you want to accomplish, what your property allows, and what the realistic costs and timeline look like.

ADU Types

ADU Options We Can Build

The right ADU type depends on your property, your goals, and your budget. Here are the options we most commonly work with in Rhode Island.

Attached In-Law Suites

A self-contained unit added to or carved out of an existing home, ideal for multigenerational living with a connected but private space.

Garage Conversions

Converting an attached or detached garage into a livable unit, often one of the most cost-effective ADU options available.

Detached Backyard Cottages

A fully separate structure on your property, offering maximum privacy for both the homeowner and the ADU occupant.

Carriage House Conversions

Restoring and converting historic carriage houses into modern living spaces, common in Newport and East Bay historic neighborhoods.

Basement Conversions

Converting an unfinished or underused basement into a legal ADU with proper egress, insulation, and finished living space.

Above-Garage Additions

Adding a living unit above an existing garage, maximizing vertical space on a property without expanding the footprint.

Pricing Guide

How Much Does an ADU Cost in Rhode Island?

An ADU in Rhode Island runs from about $80,000 for a basement conversion to $400,000 or more for a new detached cottage. Cost comes down to how much has to be built new. Converting space that already has a foundation, walls, and a roof costs far less than building a separate structure and running new utilities to it. Find the type that matches your property below. These are planning ranges, not fixed packages.

Conversion
The structure is already there. We turn a basement or garage into a legal, self-contained unit with its own kitchen, bath, egress, insulation, and utilities.
Scope of Build
Typical Range by Type
Basement Conversion$80,000–$160,000
Garage Conversion$90,000–$180,000
Attached In-Law Suite
A self-contained unit attached to or carved out of the main house, with its own entrance, kitchen, and bath. Some new framing and tie-ins to the existing home.
Scope of Build
Typical Range
Attached In-Law Suite$100,000–$200,000
Detached Cottage
A new standalone building in the backyard: foundation, framing, roof, and its own utility connections. The most construction and the most privacy.
Scope of Build
Typical Range
Detached Backyard Cottage$225,000–$400,000+
A note on these ranges: Size, finishes, septic or sewer capacity, utility runs, and the condition of the existing structure all move the number. We give you a detailed estimate after visiting your property. For a full breakdown, read the ADU Cost and Timeline Guide for Rhode Island Homeowners.

Recent Project: Studio Conversion

Backyard shed converted into a white studio with a new six-lite door and replacement windows in Middletown, Rhode Island by Toensing ConstructionSee the full project

Wondering what's currently allowed in your town? We break down ADU rules and zoning across Rhode Island on our blog.

Read: ADU Rules in Rhode Island (2026)Read: ADU Cost and Timeline Guide (2026)

How It Works

Our ADU Process, Step by Step

Every ADU project is different, but the process follows a clear path. Here is what working with Toensing Construction looks like from first call to final walkthrough.

01

Free Consultation

We start with a free on-site conversation about your property, your goals, and what Rhode Island zoning allows. No pressure, no commitment. Just honest information so you can make the right decision.

02

Design and Permitting

We work with you and your designer to develop plans that meet Rhode Island building codes and local zoning requirements, then manage the permit process from application through approval.

03

Pre-Construction Planning

Before breaking ground, we walk through a detailed scope of work, timeline, and budget together. We set clear expectations so there are no surprises once the project starts.

04

Construction

Our crew handles the build from foundation to finishes. You have a direct point of contact throughout and receive regular updates on progress, timeline, and any decisions that need your input.

05

Final Walkthrough and Closeout

We walk through the finished unit together, address any remaining items, and make sure everything meets your expectations before we close out the project.

Common Questions

ADU Questions We Hear Most Often

Do I need a permit to build an ADU in Rhode Island?

Yes. All ADU construction in Rhode Island requires building permits from your local municipality. The permitting process typically involves zoning review, plan approval, and inspections at various stages of construction. Toensing Construction manages the permit coordination as part of your project.

How much does an ADU cost in Rhode Island?

Most ADU projects in Rhode Island fall into these ranges: a basement conversion runs about $80,000 to $160,000, a garage conversion about $90,000 to $180,000, an attached in-law suite about $100,000 to $200,000, and a new detached cottage about $225,000 to $400,000 or more. Where a project lands depends on size, finishes, utilities, and existing conditions on your property. We provide a detailed estimate after visiting your property and understanding your goals.

How long does it take to build an ADU in Rhode Island?

Timeline depends on the ADU type and local permitting. A garage conversion can often be completed in a few months. A new detached structure typically takes longer once you factor in design, permitting, and construction. We give you a realistic timeline at the start and keep you updated throughout.

What are Rhode Island's ADU zoning and size rules?

Under state law (R.I. Gen. Laws § 45-24-73, updated in June 2024), towns must allow one ADU by right in three cases: on a residential lot of 20,000 square feet or more, within the existing footprint of the house or an existing accessory building such as a garage, or on an owner-occupied property to accommodate a family member with a disability. Towns can set size limits, but they must allow at least a 900 square foot studio or one-bedroom, or 60 percent of the main home's floor area, whichever is less. Individual towns may add rules for setbacks and lot coverage. We review your specific property and local zoning before the project begins so you know what is allowed on your lot.

Can I rent out my ADU in Rhode Island?

Yes, for long-term tenants. Rhode Island's ADU law was designed in part to expand housing options, and towns cannot limit who lives in an ADU by family relationship or age. Short-term rental is different: state law does not allow an ADU to be rented for tourist or transient stays or listed on a hosting platform. We recommend confirming your intended use with your local zoning office before the project starts.

Can I add an ADU to a historic home?

Potentially, yes. Historic homes involve additional considerations, including approvals from local historic district commissions and exterior design standards. Toensing Construction has experience working on historic properties across Rhode Island, and we can help you navigate the process while protecting the character of your home.

Does Toensing Construction handle everything from permits to construction?

We manage the full construction process, including permits, subcontractors, and inspections. For architectural drawings, we can coordinate with local architects and designers we trust, or work alongside an architect you already have a relationship with. Our goal is to be your single point of contact from start to finish.

Start Your ADU Project

Thinking About Adding an ADU to Your Rhode Island Property?

Start with a free consultation. We will talk through your property, your goals, and what the process looks like in Rhode Island. No pressure, no obligation. Just an honest conversation about what is possible.

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Service Areas Across Rhode Island

We build ADUs and accessory dwelling units for homeowners throughout Rhode Island, from in-law suites to backyard cottages.

BarringtonBristolCranstonEast GreenwichEast ProvidenceExeterJamestownLittle ComptonMiddletownNarragansettNewportNorth KingstownPortsmouthProvidenceSouth KingstownTivertonWarrenWarwick