ADU Builder in Harwich, MA
Mussato Building Group designs, permits, and builds ADUs in Harwich, MA, from detached guest cottages to in-law suites and garage conversions. We are a family-owned general contractor founded in 2004, with more than 100 projects completed and a 5.0 rating from 21 Google reviews. Our base in South Yarmouth is about 7 miles away, and we work across Harwich Center, Harwich Port, West Harwich, East Harwich, North Harwich, South Harwich, and Pleasant Lake.
- Family-owned since 2004
- Licensed + insured in MA
- 100+ projects completed
- 5.0 stars from 21 Google reviews
- BBB accredited
Building an ADU in Harwich
Harwich stretches from its Nantucket Sound beaches and harbors north to the ponds and cranberry bogs around Pleasant Lake.
State law allows one ADU of up to 900 square feet by right on most single-family lots, and that includes Harwich. What usually decides the project here is the lot and the septic system: an ADU with a bedroom adds to the bedroom count the system has to carry under Title 5, so we start with the Harwich Board of Health.
“Mussato Building Group has been a loyal and trusted partner of ours for over ten years and one hundred projects. Their professionalism and quality of work are second to none. We look forward to working with them far into the future.”
ADU permits in Harwich
We prepare the drawings, file the applications, and schedule the inspections. Here is what a project like this usually needs:
- Building permit from the Harwich Building Department, and a certificate of occupancy at the end.
- Review by the Harwich Board of Health of septic capacity under Title 5 if the ADU adds a bedroom.
- Zoning review of setbacks, height, and lot coverage under the Harwich zoning bylaw.
- Conservation Commission review if the ADU is within 100 feet of a wetland, coastal bank, dune, or salt marsh.
- Flood-zone design if FEMA maps the lot in an AE or VE zone.
- Detached ADUs and guest cottages
- Attached ADUs and in-law suites
- Garage and lower-level conversions
- Kitchens and bathrooms sized for small spaces
- Foundations, framing, and exteriors matched to the main house
- Heat, hot water, and electrical for a second dwelling
- Zoning, septic, and permit coordination
- Site work and paths between the houses
ADU Builder in Harwich: FAQ
Can I build an ADU in Harwich?
In most cases, yes. State law allows one ADU of up to 900 square feet, or half the size of the main house if that is smaller, by right on single-family lots in Harwich. Setbacks, septic capacity, and conservation rules still apply, so we check your lot first.
Do you build ADUs in Harwich Center and Harwich Port?
Yes. We build detached and attached ADUs all over Harwich, including Harwich Center, Harwich Port, West Harwich, East Harwich, North Harwich, South Harwich, and Pleasant Lake. Our base in South Yarmouth is about 7 miles away.
Will my septic system handle an ADU in Harwich?
Most Harwich homes are on septic systems, though the town has started adding sewer. On septic, Title 5 sizes the system by bedroom count, so an ADU with a bedroom can mean a septic upgrade. The Harwich Board of Health reviews it before the building permit.
Can I rent out an ADU in Harwich?
Long-term rentals are allowed, and the town cannot require you to live on the property. Short-term rentals of an ADU can be restricted by the town, so check the Harwich rules before you plan on summer rentals.
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