ADUs in Natick: From Concept to Permit

Thinking about adding a guest suite or rental to your Natick home? The timing is good. Massachusetts now protects one accessory dwelling unit (ADU) as an as‑of‑right use in single‑family zoning, and Natick has a clear path from concept to permit. You want clarity on what is allowed, how big you can build, what it costs, and the exact steps to approval. This guide breaks down the rules, the local workflow, and practical tips so you can move forward with confidence. Let’s dive in.

ADU basics and size limits in Natick

An ADU is a self‑contained home on the same lot as a single‑family house. Under state rules, your ADU can be no larger than the smaller of 900 square feet or one‑half of your principal dwelling’s gross floor area, and it must meet building code requirements for entry and egress. See the statewide overview for key definitions and protections in Massachusetts ADU guidance.

Natick adopted a local ADU bylaw and a structured review to align with the state law. The town’s ADU page outlines what you need for a complete filing and how projects flow to a building permit in the OpenGov portal. Start with the official Natick ADU project page and FAQ.

What the new state law changed for you

State regulation 760 CMR 71.00 makes a single ADU an as‑of‑right use in single‑family districts and sets statewide limits and definitions. Municipalities cannot require owner occupancy or a special permit for a protected ADU, and parking requirements are capped. Review the full regulation at 760 CMR 71.00.

Parking rules are straightforward: if your property is within one‑half mile of MBTA service, the town cannot require off‑street parking for the ADU; beyond that distance, the town cannot require more than one space. This is especially relevant near Natick Center and West Natick commuter rail stations. You may rent your ADU, but short‑term stays of 31 days or less are excluded in the ADU framework. Details are in the state ADU overview.

Natick ADU types and why they matter

Natick classifies ADUs to route your application efficiently. Knowing your type helps you plan drawings, approvals, and timelines. The types below come from the town’s filing guidance:

• Type 1: Entirely within the existing home, including attached garage conversions, or conversion of an existing detached garage more than 10 feet from the house under set conditions.
• Type 2: Detached ADU within the allowable building envelope, or an addition that does not need dimensional relief.
• Type 3: Projects that need findings or relief for intensity or dimensional rules.
• Type 4: Two or more ADUs on a lot, or anything requiring a variance or special permit.

Read the town’s definitions and submittal checklist in the ADU Application Review Filing Guidance.

Step‑by‑step: Natick’s permit path

Follow this sequence to reduce surprises and keep your project on schedule:

1. Early feasibility

• Confirm zoning, lot constraints, and utilities. Identify sewer vs septic and any prior ZBA relief on your property. Start with the Natick ADU project page.

2. ADU Application Review (Part 1)

• File through OpenGov with site plan, floor plans, gross floor area calculations, utility information, and required attachments. The town issues a Building Commissioner’s Letter of Determination that guides your building permit. Use the town’s filing guidance and checklist.

3. Board of Health / Title 5 if on septic

• If your home is on a septic system, expect a Title 5 building review and possible upgrades if design flow increases. Learn the basics in MassDEP’s Title 5 regulations.

4. Building permit and trade permits

• Submit construction drawings that meet the Massachusetts Building Code and Natick’s Stretch Code requirements. Check fees and apply online via the Natick Building Department.

5. Inspections and Certificate of Occupancy

• After final inspections, the town issues your Certificate of Occupancy and records ADU data under the state regulation. See the regulatory framework at 760 CMR 71.00.

Costs, timeline, and utilities

Budget ranges vary by site and scope. Internal conversions like basements or attached garages are usually the least expensive, often cited around 75,000 to 150,000 dollars in regional examples. Detached ADUs frequently run 150,000 to 400,000 dollars or more depending on foundation, utilities, and finishes. For ballpark context, see the ranges cited in Boston’s ADU FAQ.

Most projects need electrical service upgrades, new plumbing, HVAC, and water or sewer connections. If you are on septic, plan for Title 5 review and the possibility of system upgrades if design flow increases. Early coordination with the Board of Health helps keep your schedule intact. Timelines often run 6 to 12 months from feasibility to move‑in, with more time for detached or relief‑seeking projects. Natick’s two‑part process is designed to reduce surprises once you reach the building permit phase. See the submittal details in the town’s Application Review Filing Guidance.

Multiple ADUs and affordability triggers

A single ADU is protected by state law as an as‑of‑right use. If you plan two or more ADUs on one lot in Natick, you will need a Special Permit, and the combined ADU square footage may be capped. In some multi‑ADU cases, one unit may need to be deed‑restricted as affordable under local inclusionary rules. The town describes these cases in its filing guidance.

Quick planning checklist

Use this to structure your first 30 days:

• Measure your principal dwelling’s gross floor area to confirm your ADU’s maximum size under the statewide cap.
• Identify sewer vs septic and gather any past zoning decisions tied to your lot.
• Sketch the ADU type that fits your property and budget, then verify setbacks and building envelope.
• Contact Natick CED, the Building Department, and the Board of Health to confirm expectations.
• Prepare the ADU Application Review package with plans, GFA calculations, utilities, and Title 5 items if applicable. Start with the Natick ADU page and the Application Review checklist.

Selling or buying with an ADU in Natick

An ADU can add livable area and potential rental income, which can support value. The key on resale is documentation. Keep your ADU Application Review, building permits, inspection sign‑offs, and Certificate of Occupancy organized for buyer due diligence. Natick notes that existing illegal ADUs remain illegal until they are permitted, so regularizing an older, unpermitted unit is worth addressing before you list. You can confirm local rules on the Natick ADU project page.

Ready to map your ADU’s impact on value or plan a sale that showcases the space well? Reach out to Felicia Captain for a data‑driven pricing conversation and a tailored marketing plan.

FAQs

How big can an ADU be in Natick?

• Under state rules and Natick’s bylaw, your ADU must be the smaller of 900 square feet or one‑half of your principal dwelling’s gross floor area; see the state ADU guidance.

Do I need to live on the property to have an ADU?

• No. The state regulation prohibits owner‑occupancy requirements for protected ADUs; see 760 CMR 71.00.

What are the ADU parking rules near MBTA stations?

• If your lot is within one‑half mile of MBTA service, Natick cannot require off‑street parking for your ADU; outside that radius, no more than one space can be required, per the state ADU overview.

How does a septic system affect my ADU plan?

• If you are on septic, expect a Title 5 review and possible upgrades if design flow increases; start early with the Board of Health and review MassDEP’s Title 5 regulations.

What is the permit sequence for an ADU in Natick?

• File the ADU Application Review in OpenGov, address Board of Health items if on septic, then submit your building permit for construction and trade work; see the town’s Application Review guidance.

How much does an ADU cost and how long does it take?

• Internal conversions often run about 75,000 to 150,000 dollars and detached units frequently range from 150,000 to 400,000 dollars or more; many projects run 6 to 12 months from feasibility to move‑in, as outlined in Boston’s ADU FAQ and Natick’s filing guidance.