ADU Builder in Eastern Connecticut | In-Law Suites & Accessory Dwellings

Eastern Connecticut’s ADU Builder — 26 Years In Your Backyard

Lagace Construction is based in Andover, Connecticut — the heart of Tolland County — and we’ve been building across eastern CT since 1998. When you call us about an ADU, you’re not talking to a call center in another state or a new company chasing a trend. You’re talking to contractors who’ve pulled permits in Coventry, Mansfield, Windham, and Colchester. We know the eastern CT building departments by name.

Connecticut’s 2026 ADU law changed everything for homeowners in our region. Most towns across Tolland County, Windham County, and the greater New London area now allow at least one accessory dwelling unit on a single-family lot — by-right or with a streamlined approval process. The legislature opened the door. Now it takes a contractor who understands what comes next: the local zoning board quirks, the well and septic considerations that come with rural eastern CT properties, the specific inspectors in each town, and the real costs of getting an ADU built right the first time.

We build every type of ADU: basement conversions, attached in-law additions, detached backyard cottages, and garages with living space above. If you own land in eastern Connecticut and you’re thinking about adding an ADU — for aging parents, rental income, or a family member who needs independence — we’re the crew that knows how to make it happen efficiently, on budget, and built to last. Our CT Home Improvement license (#NHC-0016939) and Electrical license (#E1-00191661) mean we handle the full project, not just pieces of it.

Call us at (860) 371-5511 for a free, no-pressure estimate. We’ll walk the property, talk through your goals, and give you real numbers — not ballpark guesses designed to win your business and change later.

Eastern Connecticut ADU Cost Guide — 2026

Cost ranges below reflect real eastern CT labor rates, material costs, and typical permitting fees as of 2026. Eastern Connecticut is generally more affordable than Fairfield County or the shoreline, but costs have risen with material prices and labor demand. These are honest ranges based on projects we’ve completed in our region — not inflated numbers pulled from national averages.

ADU Type Typical Size Eastern CT Cost Range
Basement Conversion 400–700 sq ft $80,000–$150,000
Attached In-Law Addition 400–800 sq ft $150,000–$280,000
Detached Cottage / Studio 400–700 sq ft $200,000–$380,000
Garage with Living Above 500–900 sq ft $220,000–$420,000
⚠ Septic Note for Rural Eastern CT Properties:

A large share of eastern Connecticut properties — particularly in Tolland and Windham counties — are on private well and septic systems rather than municipal utilities. If you’re adding a detached ADU or a larger attached addition, your existing septic system may require an upgrade or a second system. Septic work in eastern CT typically runs $15,000–$40,000 depending on lot conditions, soil perc tests, and the scope of the upgrade. We coordinate directly with licensed septic engineers during the planning phase so there are no surprise costs after construction begins.

Basement conversions are the most cost-effective option where the foundation already exists and ceiling height allows — many split-level and raised-ranch homes in eastern CT are ideal candidates. Detached cottages and garage-over-living-space builds carry higher costs but add permanent square footage and stronger long-term value. We’ll help you evaluate which type makes the most financial sense for your specific property and goals.

Eastern Connecticut Towns We Serve

We cover all of Tolland County, all of Windham County, and the greater New London and Middlesex area. If you’re in eastern CT, we’re in your region — no long-haul travel charges, no unfamiliar local codes.

Eastern CT ADU Zoning — What the 2026 Law Means for You

Connecticut’s 2026 ADU legislation was a significant shift in state housing policy. Under the new law, municipalities across Connecticut — including the towns of Tolland and Windham counties — are required to allow at least one accessory dwelling unit on any single-family residential lot that meets basic size thresholds. This ends years of blanket bans and overly restrictive local zoning that made ADUs nearly impossible in many rural and suburban communities.

In practical terms for eastern CT homeowners: if you own a single-family home in Coventry, Mansfield, Ellington, Woodstock, or most other towns in our service area, you now have a legal pathway to add an ADU. The specifics still vary by town. Some municipalities have adopted by-right ADU approval — meaning no public hearing required, just a building permit application. Others still require an administrative review or a zoning variance, but the bar is lower than it was before 2026.

Where eastern CT gets more complicated than, say, a Hartford suburb is the prevalence of rural lot conditions. Many properties in Windham County, Tolland County, and the New London area are served by private wells and septic systems rather than municipal water and sewer. State ADU law addresses land use — it does not exempt you from septic capacity requirements. If your existing system is sized for a single household, adding a second dwelling unit may trigger a septic evaluation and possible upgrade before the building department will issue your ADU permit. This is not a dealbreaker — it’s a planning step, and we work through it regularly — but it’s something to account for in your budget and timeline from day one.

Setback requirements, maximum ADU square footage, and owner-occupancy rules are areas where the details still differ across eastern CT towns. Some towns cap detached ADU size at 800 square feet; others allow up to 1,200. Some require the primary homeowner to occupy either the main home or the ADU. We keep current on all of these details for every town we work in. For a full town-by-town breakdown, see our Connecticut ADU Zoning Guide.

Bottom line: the 2026 law opened the door for most eastern CT homeowners. The path from that open door to an occupied ADU requires a contractor who understands both the state framework and the local fine print. That’s us.

Why Eastern CT Homeowners Choose Lagace Construction

  • ✓

    We’re local — Andover-based, eastern CT built. We’re not a regional franchise or a company that drives three hours to your job. Our crews live and work in the same communities as our clients. That matters when a problem comes up on a Tuesday at 7 AM.
  • ✓

    We know every eastern CT building department. Tolland, Coventry, Mansfield, Windham, Putnam — we’ve pulled permits in all of them. We know who the inspectors are, what they look for, and how to run a clean project that doesn’t get held up on technicalities.
  • ✓

    26+ years of Connecticut construction experience. Since 1998. We’ve seen interest rates change, material costs spike, building codes update, and housing markets shift. We’ve built through all of it. That kind of longevity means we’ve solved problems you haven’t encountered yet.
  • ✓

    Skilled local crew — not out-of-state subs. We do not ship in temporary labor from out of state or cobble together projects with a dozen different subcontractors. Our skilled local crew has worked together for years. That consistency shows in the finished product and in how the job runs day to day.
  • ✓

    Fully licensed and insured in Connecticut. CT Home Improvement Contractor license #NHC-0016939. CT Electrical license #E1-00191661. We carry full liability and workers’ comp. You’re protected from day one to the final walkthrough.
  • ✓

    ★ 4.9 Google rating. We don’t pad our reviews or push clients for five stars while problems go unresolved. Our rating reflects real projects for real eastern CT homeowners — and we take it seriously.

Eastern Connecticut ADU — Frequently Asked Questions

Are ADUs legal in eastern Connecticut towns?

Yes. Connecticut’s 2026 ADU law requires most municipalities to allow at least one ADU per single-family residential lot. This covers the overwhelming majority of towns in Tolland County, Windham County, and the broader eastern CT region. Local rules about setbacks, size, and utility requirements still apply, but blanket ADU bans are no longer permitted under state law. Some towns have fully adopted by-right ADU approval; others still require an administrative zoning review. We can tell you exactly where your town stands before you commit to anything.

Do eastern CT rural lots need a new septic system for an ADU?

Not always, but it’s one of the most important questions to answer early. If you’re adding a detached ADU or a larger addition, your local building department will typically require documentation that your existing septic system can handle the added load. If it can’t, you’ll need an upgrade or a second system before the permit is issued. A soil perc test and a licensed septic engineer’s evaluation will give you a definitive answer. We build this step into our project planning from the start so there are no surprises. Septic work in eastern CT typically runs $15,000–$40,000 depending on scope and lot conditions.

How much does an ADU cost in eastern Connecticut?

Eastern CT costs are generally more moderate than the Hartford suburbs or the shoreline, but real ADU construction is not cheap. Basement conversions typically run $80,000–$150,000. Attached in-law additions run $150,000–$280,000. Detached cottages and garage-with-living-above projects run $200,000–$420,000. These ranges reflect 2026 labor and material costs. If a septic upgrade is needed, add $15,000–$40,000. We provide detailed, itemized estimates — not ballpark guesses — so you know exactly what you’re committing to before construction starts.

What towns in eastern CT does Lagace Construction serve?

We serve all of Tolland County (Andover, Bolton, Columbia, Coventry, Ellington, Hebron, Mansfield, Somers, Stafford, Tolland, Vernon, Willington), all of Windham County (Ashford, Brooklyn, Canterbury, Chaplin, Eastford, Hampton, Killingly, Lebanon, Plainfield, Pomfret, Putnam, Scotland, Sterling, Thompson, Windham, Woodstock), and select New London and Middlesex area towns including Colchester, East Haddam, and Salem. If your town isn’t listed, call us — we may still be able to help.

How long does it take to permit an ADU in eastern CT?

Permit timelines vary by town and ADU type. For straightforward basement conversions with complete plans, some eastern CT building departments can turn permits around in 3–6 weeks. Detached structures and larger additions may take 6–12 weeks, especially if engineering drawings, septic review, or a zoning board review is required. Towns that have adopted by-right ADU approval under the 2026 law tend to move faster. We prepare complete permit packages — plans, specs, site data — so nothing gets sent back for missing information. We also follow up with the building department on your behalf throughout the process.

Can I rent my ADU in Connecticut?

Yes. Connecticut law permits ADU rentals. Whether you rent to a long-term tenant, use it as a short-term rental, or house a family member, the ADU is a legal dwelling unit once it’s permitted and inspected. Some municipalities that still have owner-occupancy requirements may require you to live in either the main home or the ADU — but they cannot prohibit you from renting the other unit. Short-term rental platforms like Airbnb may be subject to additional local regulations depending on your town. We recommend confirming rental-specific rules with your town’s zoning office, but the baseline right to rent a permitted ADU is protected by state law.

What’s the difference between an ADU and an in-law suite?

In common usage, “in-law suite” and “ADU” are often used interchangeably — and in Connecticut, an in-law suite that includes its own kitchen, bathroom, and sleeping area is legally classified as an accessory dwelling unit. The key distinction from a practical and permitting standpoint is whether the space functions as an independent dwelling: its own entrance, its own kitchen, its own bath. A guest bedroom with a shared bathroom and no kitchen is not an ADU. A self-contained apartment attached to or detached from your home — even if you call it a granny flat or in-law apartment — is an ADU and must be permitted as one.

Do you build detached ADUs in rural eastern CT?

Yes. Detached backyard cottages and studios are one of our most requested ADU types — especially on larger rural lots in Windham and Tolland counties where there’s room to build. Detached ADUs are the most involved type because they require their own foundation, framing, roofing, utilities, and often a dedicated electrical service. They’re also typically the most valuable addition to a property long-term. We handle site prep, foundation, full framing, insulation, mechanical, electrical, plumbing, interior finishes — everything from ground breaking to final inspection. Septic planning is coordinated early for rural lots.

What’s the minimum lot size for an ADU in Connecticut?

Connecticut’s 2026 ADU law does not set a single statewide minimum lot size — municipalities set their own size thresholds within state guidelines. In many eastern CT towns, ADUs are permitted on lots as small as one-half acre, and some municipalities allow them on smaller lots if served by municipal sewer. In rural areas where well and septic are required, lot size is often tied to septic capacity rather than zoning thresholds. We’ll evaluate your specific lot and tell you exactly what’s possible before you spend time or money on plans. Many homeowners assume their lot is too small — and turn out to be wrong.

Does Lagace pull all the permits?

Yes — always. We pull every permit required for your project: building, electrical, plumbing, mechanical, and any zoning approvals. Permit-pulling is not something we push onto homeowners or subcontractors. As the licensed general contractor, we are responsible for the project being built to code and fully inspected, and that starts with us owning the permit process. Our CT Home Improvement Contractor license (#NHC-0016939) and CT Electrical license (#E1-00191661) give us the authority to do this across eastern Connecticut. If a contractor suggests you pull your own permit as a homeowner to “save money,” that’s a red flag — it shifts liability onto you and often voids homeowner’s insurance coverage during construction.