In-Law Suite Additions in Connecticut | Floor Plans, Costs & Permit Info

What Should Be Included in an In-Law Suite?

Whether you’re building a simple 1-bedroom unit or a spacious 2-bedroom apartment for your parents, the best in-law suites are designed to balance independence, accessibility, and comfort. Here’s what we recommend including:

• Private Bedroom: A quiet space for rest and personal time.
• Full Bathroom: Ideally with a walk-in shower and grab bars for safety.
• Kitchenette: A small but functional cooking area with storage and appliances.
• Separate Entrance: Gives your loved one privacy and autonomy.
• Open Living Area: A shared space for relaxing, watching TV, or hosting guests.
• Accessibility Features: No-step entry, wider doorways, lever-style handles, and single-level design.
• Climate Control: A dedicated thermostat or HVAC zone for comfort year-round.

Many homeowners also request extra insulation, a stacked laundry unit, or a small patio area. Our Connecticut home addition team works closely with each client to customize these features based on space, zoning, and lifestyle needs.

How Much Does It Cost to Build an In-Law Suite in Connecticut?

The cost of building a mother-in-law suite in Connecticut depends on several key factors—size, layout, location on the property, and the level of customization. At Lagace Construction, we typically see in-law suite additions fall into the following ranges:

• Attached In-Law Suites: $110–$225 per square foot
• Detached In-Law Apartments: $150–$300 per square foot
• Prefab Units: Starting around $85,000+, depending on site prep and delivery

Smaller 400–600 sq ft units (1-bedroom, 1-bath, kitchenette) generally cost $65,000–$120,000 when built as an addition. Larger, fully independent 2-bedroom units with ADA upgrades, laundry, and full kitchens can exceed $175,000+.

What Drives the Price?

Here are the most common cost factors we walk our Connecticut clients through:

• Foundation work: Slab-on-grade vs full foundation for basements or crawl spaces
• Utility connections: Electrical, plumbing, HVAC—shared or separated from the main house
• Custom features: Built-ins, ADA compliance, covered entryways, patio, mini-split systems
• Zoning or grading prep: Particularly for rural or sloped lots in towns like Hebron or Tolland
• Interior finishes: Flooring, cabinetry, appliances, tile, lighting packages

Some homeowners ask about the cheapest way to build a mother-in-law suite. Prefab or modular units can save on labor and build time, but they often come with additional costs like delivery crane access, foundation setup, and septic upgrades. Plus, customization is limited.

If you’re comparing prefab vs custom, it’s not just about upfront price—it’s about long-term livability, integration with your property, and resale value. Request a consultation and we’ll walk you through real numbers based on your space and goals.

Permits, Zoning & Regulations for In-Law Suites in Connecticut

Before building an in-law suite in Connecticut, it’s important to understand the local regulations that apply to your property. Most towns treat these additions as Accessory Dwelling Units (ADUs), which are subject to zoning, septic, and structural codes. The requirements vary depending on where you live, and whether the unit is attached, detached, or above a garage.

Do I Need a Permit for an In-Law Suite?

Yes. In almost every Connecticut town, you’ll need a building permit—and often additional approvals—for the following:

• Structural modifications (foundation, framing, roofing)
• Plumbing and electrical work for the bathroom and kitchenette
• HVAC upgrades (new zones or separate systems)
• New entrances or driveways
• Changes to water/sewer or septic systems

Common Zoning Requirements

Each town has different rules, but here’s what we often see in areas like Manchester, Glastonbury, Vernon, Tolland, and Hebron:

• Lot size minimums: Some towns require a certain square footage to add a detached unit.
• Owner occupancy: Many towns require the homeowner to live on the property full-time.
• Size limits: In-law suites are often capped at 30–50% of the primary home’s square footage.
• Setback rules: Detached units must maintain minimum distances from property lines.

In some towns, a zoning variance or special use permit may be required—especially for larger in-law apartments or when adding a second kitchen. Lagace Construction helps homeowners navigate these local requirements and handles all permitting and inspections as part of our build process.

What If I’m on a Septic System?

If your home uses a septic system, you may need to upgrade or expand it to accommodate an additional bedroom. This usually involves a site evaluation and approval from the Connecticut Department of Public Health or your local health district.

🏠 1-Bedroom Attached Suite with Private Entrance

This layout is perfect for smaller homes or ranch-style builds. It includes a private bedroom, full bathroom, kitchenette, and small living area—plus its own entrance for added privacy. Everything is on one level to support aging-in-place comfort.

🏘️ Detached 2-Bedroom In-Law Suite with Patio

Ideal for larger families, this 2-bedroom layout provides full independence while still being close by. Includes two bedrooms, a shared bathroom, a full kitchen, and a spacious living area. Some clients also opt for a small patio or covered entry.

We’ve built versions of this in Tolland and Hebron where zoning allowed detached accessory dwellings. We can help you find out what’s permitted on your lot.

🏠 1-Bedroom Attached Suite with Private Entrance

This efficient layout includes a private bedroom, bathroom, kitchenette, and small living area—all on one level. It’s ideal for ranch homes and aging parents who need easy access with minimal stairs. A private entrance gives them autonomy while keeping them close by.

🏡 Over-Garage 1-Bedroom In-Law Apartment

Perfect for properties with limited yard space, this apartment includes a full kitchen, open living area, bedroom, and bath—all built over a garage. We’ve built this style for several Connecticut families needing a more private setup without expanding outward.

🏘️ Detached 2-Bedroom In-Law Suite with Patio

This spacious design includes two bedrooms, a shared bath, a full kitchen, and a living room—plus the option for a private patio. It’s ideal when zoning allows for a detached ADU and you want to provide full independence for loved ones.

Attached vs Detached In-Law Suites: Which Is Right for You?

One of the first decisions homeowners face is whether to build an attached or detached in-law suite. Each has its own advantages and considerations depending on your space, zoning, budget, and long-term goals. Here’s how they compare:

🏡 Detached In-Law Suite Benefits

• Maximum privacy for your parents and family
• Separate entrance creates full independence
• Potential to use the space later as a guesthouse or rental unit
• Can increase long-term property value more significantly

Considerations:

• Higher upfront cost due to separate utilities and foundation
• Requires larger lot and may trigger stricter zoning or variance needs
• Longer timeline with more site prep and coordination

Not sure which route makes sense for your property in Tolland, Glastonbury, Vernon, or elsewhere in Connecticut? At Lagace Construction, we help homeowners weigh every option based on zoning, lifestyle needs, and long-term plans. Book a free consultation and we’ll walk you through what works best for your home and your family.

Prefab vs Custom-Built In-Law Suites: What’s Right for Your Home?

When planning an in-law addition, one question we hear often is: “Would prefab be cheaper?” The answer: it depends—but cheaper isn’t always better. Here’s a breakdown of how prefab in-law suites compare to a custom addition

Why Most Connecticut Homeowners Choose Custom

Custom additions are built to fit your home’s layout, your family’s needs, and your property’s zoning limits. At Lagace Construction, we help clients create in-law suites that don’t just meet building codes—they feel like home.

• Pros:
  • Seamless integration with your existing home or landscape
  • Total control over size, features, finishes, and layout
  • Better long-term value and comfort
  • Easier to match architectural style for curb appeal
• Cons:
  • Typically higher up-front cost
  • Slightly longer construction timeline

If you’re comparing prefab vs custom in-law suites in Connecticut, we’re happy to walk you through both options—cost, timeline, and zoning included. Schedule a consultation and get clear answers from a licensed local builder who knows the process inside and out.

How to Get Started with Lagace Construction

Building an in-law suite is a big decision—but it doesn’t have to feel overwhelming. Whether you already have floor plans in mind or you’re just starting to explore your options, our team is here to guide you every step of the way.

At Lagace Construction, we offer:

• Personalized consultations to understand your family’s needs
• Design assistance based on your space, goals, and town zoning rules
• Full-service permitting and code compliance
• Custom construction using durable materials and aging-in-place features

We’ve helped homeowners across Andover, Glastonbury, Manchester, and Tolland create beautiful in-law suite additions that provide comfort, privacy, and peace of mind. Let’s talk about what’s possible for your property.

Schedule your free in-law suite consultation and get expert guidance tailored to your home, your budget, and your family.