1. What is an ADU and how does New Hampshire law affect what I can build?

An Accessory Dwelling Unit (ADU) is a secondary dwelling on the same property as a single-family home. Thanks to New Hampshire’s House Bill 577 (effective July 1, 2025), homeowners now have by-right permission to build both attached and detached ADUs in any zone that allows single-family homes, subject to the same basic standards (setbacks, height, lot coverage, etc.). The law also raises the maximum ADU size to 950 sq ft in many communities. For more detailed guidance, see the state’s official Accessory Dwelling Unit Guide for Homeowners (RSA 674:71–73). We offer a free Zoning Analysis tool so you don’t have to try and figure it all out on your own!

2. Who is Granite State ADU and what makes you different?

Granite State ADU is a new design–build company created by two long-time New England building professionals:

• Tuscher Design Group founder Brayden Tuscher, known for high-quality residential architectural design.

• Econeered by Design founder Erik Jones, with decades of hands-on construction experience.

Together they formed Granite State ADU to focus exclusively on well-designed, efficient, and affordable ADUs that meet the growing demand created by HB 577. This partnership blends deep design expertise with proven construction know-how, giving homeowners a single point of accountability from zoning analysis through final build.

3. Why are Granite State ADUs not “tiny homes”?

Many “tiny homes” are treated as manufactured or mobile housing and often are not permitted by local zoning. Granite State ADUs are permanent, code-compliant homes built to the International Residential Code (IRC) and New Hampshire building standards with full utilities and foundations. We offer both traditional site-built methods and modular construction options depending on your needs—both result in legal, mortgage-eligible ADUs wherever HB 577 applies.

4. What are the financial advantages of building an ADU?

A well-planned accessory dwelling unit can be a smart long-term investment. By creating a fully independent rental space, an ADU can generate steady monthly income—often enough to offset mortgage or property-tax costs. Because it adds flexible, code-compliant living space, an ADU typically increases overall property value beyond the cost of construction.

An ADU also supports multi-generational living. For example, you can create a comfortable, private home for aging parents or in-laws on the same property. This arrangement can significantly reduce or even eliminate future expenses for assisted-living or senior housing while keeping loved ones close. The ability to share care, meals, and household responsibilities can free up time and money and provide peace of mind for everyone involved. Grandparents onsite to help with child care costs - YES!

5. How much does it cost to build an ADU?

Cost depends on size, finishes, site conditions, and whether it’s detached or attached. A compact 550 sq ft plan with standard finishes will cost less than a larger custom design or one with premium materials or an attached garage. We provide transparent, itemized budgets during design so you can align scope and cost early.

6. Do you offer financing options?

Yes. Granite State ADU partners with Merrimack Savings Bank, which offers construction loans specifically for accessory dwelling units. We coordinate plans and budgets with their team to streamline approvals.

7. What are the advantages of a detached ADU versus an attached one?

Detached ADUs typically provide more privacy, site-planning flexibility, and fewer constraints from the existing structure. Attached ADUs can suit certain properties but may require more structural coordination and oftentimes higher costs. We design and permit both and will recommend the best fit for your lot and budget.

8. How long does the process take and what are the 4 easy steps?

We keep it simple with 4 easy steps:

1. Zoning Analysis — a free review to confirm what your lot allows and flag any issues.

2. Site Visit — align goals and evaluate existing structures and site conditions.

3. Design — a custom plan tailored to your needs, site, and budget (we can also help coordinate financing).

4. Construction — we handle permitting and build your ADU with a clear schedule and regular updates through move-in.

This structured process keeps timelines clear and efficient while ensuring your ADU is designed and built right the first time.

9. What sizes and layouts do you offer?

Our catalog ranges from about 550 sq ft one-bedroom cottages to 950 sq ft two-bedroom homes. Every plan is fully customizable at no additional charge to fit your lot, lifestyle, and the allowances under HB 577. Please visit our Design Section to get the ideas flowing!

10. Are your designs ADA-compliant and aging-in-place ready?

Yes. Most plans are single-level and ADA-friendly, with features like wider doors, accessible bathrooms, minimal thresholds, and accessible kitchen layouts to support safe, comfortable long-term living.

11. Do I need a new septic system?

In most cases, no. New Hampshire law (RSA 674:72 V) does not require a brand-new septic system when adding an ADU unless the existing system is failing or unapproved. Typically, the only requirement is to have an updated septic design prepared and filed with the New Hampshire Department of Environmental Services (DES). Granite State ADU works with licensed septic designers across the state and can coordinate everything for you—from design updates and state paperwork to local approvals—so the process is seamless and doesn’t delay construction

12. Do you help with zoning and permits?

Absolutely. We offer a free Zoning Analysis tool to get you started, then we prepare applications, attend municipal meetings, and coordinate all approvals. Our goal is a clear, efficient path from first conversation to building permit.