Building permits, zoning and septic rules across New Hampshire

None. New Hampshire has 0 counties with a blanket no-residential-building-permit answer, 3 with limited requirements and 7 where unincorporated land needs a residential building permit¹. The limited group is Grafton County, Sullivan County and Strafford County; limited means a permit applies only in some cases, not a general exemption¹. The best-scoring counties that require one are Carroll County, Coos County and Cheshire County¹.

Owner-builders get a conditional plumbing-license exemption, not a statewide exemption from building permits or inspections; the owner-builder county list is a starting point^3,8. County lines matter less here than the town: the building permit process depends on whether the town enforces the state code³.

Where a town has adopted a local enforcement mechanism for the state building code, the permit follows that town's process, and the building official must approve or deny a completed application within 30 days¹⁰. Where a town has not, the state building permit system excludes one- and two-family dwellings, so a house there is not permitted through the State Fire Marshal; local requirements may still apply if the town has an ordinance³. The State Fire Marshal's office handles questions about the state system¹¹.

Under the state system, electrical, plumbing, mechanical and fire-protection work each need a separate permit, and the state's published fee for other structures and uses is $1.00 per gross square foot with a $35 minimum; that schedule excludes one- and two-family dwellings¹². Inspections are requested by the permit holder before work is concealed¹². Towns may also require a certificate of occupancy before you use a new building¹².

A county with unincorporated towns or unorganized places may set up its own building-code enforcement or require permits for buildings on leased land there^13,14.

County-wide zoning is absent in 5 New Hampshire counties: Grafton County, Carroll County, Sullivan County, Cheshire County and Belknap County⁴. Another 5 have county zoning: Coos County, Hillsborough County, Merrimack County, Strafford County and Rockingham County¹. See the no-zoning county list.

State law lets a county adopt zoning only for its unincorporated towns and unorganized places, while towns divide themselves into districts with different rules^6,15. Lot size, setbacks, lot coverage and building height are therefore set by the district, with no statewide number¹⁵.

Subdividing also runs through the town: a planning board regulates subdivision only where the municipality has authorized it¹⁶. Ask the town planning office for the parcel's district before you buy.

The New Hampshire Department of Environmental Services approves septic plans across all 10 counties, though local plan approval may also be required and inspections can be delegated to qualified municipal officials^1,7. No one may build a structure that will discharge sewage, or a disposal system, without prior DES approval of the plans⁵.

Plans must come from a permitted New Hampshire septic system designer, and you need both an Approval for Construction and an Approval for Operation before use¹⁷. A system must pass final inspection before it is covered or put into operation, and tanks must be inspected for sludge and scum often enough to be pumped when the layer reaches one-third of tank depth¹⁸.

A composting or incinerator toilet avoids DES approval only where the structure has no internal plumbing and no supplied water; with plumbing and water, an approved disposal system is required even if the toilet is not connected to it¹⁸.

We could not confirm a county-level answer on private-land RV living in any of New Hampshire's 10 counties, and none on tiny homes either¹. That gap is neither permission nor prohibition: ask the parcel's town zoning office and building official about RV use, temporary occupancy while you build and any tiny-home structure.

The state's campground rules cover temporary recreational occupancy at campgrounds, not permanent living on your own house lot, and municipalities keep authority to enforce local zoning and health-and-safety rules¹⁹. Any dwelling still falls under the state building code, and zoning is set town by town^2,6.

Grafton County leads the Bolthole Index at 83/100, followed by Carroll County and Sullivan County at 81/100; Grafton and Sullivan have limited building permit requirements, Carroll requires building permits, and none has county-wide zoning^1,4. Coos County scores 77/100 and requires building permits and has county zoning¹.

The median county farmland value is $6,630 per acre; Coos County is lowest at $4,071 per acre, followed by Grafton County at $4,312¹. Those are farmland benchmarks, not asking prices for a building lot. The median county effective property tax rate is 1.95% and the median county bill is $5,796 per year¹.

Domestic wells are exempt from the large-groundwater-withdrawal permit regime, but the contractor must give the Water Well Board a completion record within 90 days after the well is finished^9,20. Open-loop geothermal wells need a separate groundwater discharge permit⁹.

Plan water and wastewater together: supplied water and internal plumbing trigger an approved sewage disposal system even with a composting toilet¹⁸. New Hampshire also generally requires connection to a public sewer within 100 feet, and a town may increase that distance or grant waivers for adequate alternatives, so ask the municipal health office before commissioning septic plans²¹.