| Zone | Front | Rear | Side | Height | Max coverage |
|---|---|---|---|---|---|
| R1 | 35 ft | 30 ft | 15 ft | 45 ft | 50% |
| R2 | 25 ft | 20 ft | 7 ft | 35 ft | 60% |
| R5 | 20 ft | 15 ft | 7 ft | 50 ft | 65% |
Setbacks for the house itself under current county law (§18-4-501, -601, -701). The county is considering a rewrite of the zoning code (Bill 61-26) in October 2026, so confirm the current numbers for your lot.
1. The permit
An addition, which the county defines as an outward or upward extension, is filed as a Residential Single Family Dwelling permit in the Land Use Navigator. Expect to upload:
- The building permit application.
- Construction plans drawn to an architectural scale with dimensions and materials.
- A site plan drawn to an engineering scale, showing property lines, easements, rights of way and any well, septic system or grinder pump.
- A Critical Area worksheet and a standard grading plan application, where they apply.
Electrical, plumbing, gas and mechanical work each need their own trade permit, pulled by a licensed tradesperson.
2. Setbacks, height and coverage
The table above shows the setbacks for a house in the most common residential zones. An open deck attached to the house may project up to 10 feet into the rear setback if it stays at least 3 feet from the lot line. On an older lot that is smaller than today's standards, the county allows a house to expand with 25-foot front and rear setbacks, 7-foot sides and a 35-foot height limit. If the addition can't fit, the alternative is a variance, which adds months.
3. Grading and the Critical Area
Any ground disturbance needs grading approval. A standard grading plan covers projects that disturb 5,000 square feet or less, with cuts or fills under 10 feet and 100 cubic yards, no slopes of 15% or more, and nothing in the 100-year floodplain or within 100 feet of tidal water, streams or tidal wetlands. Larger or steeper sites need a full grading permit. Near the water, Critical Area lot coverage is a separate limit from zoning coverage; see our Critical Area guide.
4. Septic and well
On septic, the Health Department checks whether the system can handle added living space, and the lot needs room for two future replacement systems. Required septic upgrades must be done before the Health Department signs off. If a site can't meet conventional requirements, a "limited home addition" may be possible: up to 50% more living space, capped at 1,000 square feet, with no new bedrooms and an advanced pretreatment unit. See our septic guide.
5. Flood zones
If the project costs 50% or more of the building's market value, it is a "substantial improvement" and the whole house must meet flood rules, with the lowest floor at least 1 foot above the 100-year flood elevation. Below that threshold, only the addition itself has to be elevated. See our flood-zone guide.
6. Inspections and fees
Inspections are scheduled in the Land Use Navigator and typically run footing, foundation, framing, insulation and final, with trade inspections along the way. The building permit fee is based on the cost of the work: a $150,000 addition works out to $1,492, plus the $43 application fee and trade permits. Try our permit fee calculator, or read how the permit process works.
