1. 
No building or structure shall be built nor shall any existing building or structure be enlarged or altered except in conformance with the regulations of this Zoning Ordinance as to lot coverage, lot area, area per dwelling unit, lot width, front, side and rear yards, and maximum height of structures, in the several districts as set forth herein, except as may otherwise be provided in this Ordinance.
Side lot lines may deviate from this requirement for natural constraints, such as watercourses, wetlands, etc., or where prudent subdivision practices necessitate special consideration. In all such cases the burden shall be on the applicant to justify such deviations in design.
2. 
Lot lines to be substantially at right angles to street lines. Side lot lines shall be substantially at right angles to straight street lines, or radial to curved street lines, for their full length from front to rear.
3. 
The land and yard space required for any new building or use shall not include any land or area required by any other building or use to fulfill zoning requirements.
4. 
Developable land area.
This provision shall not apply to any lot of less than two (2) acres in area existing and recorded as of July 1, 1994.
For the purpose of calculating the minimum lot size required by this Ordinance or calculating the maximum number of units, maximum lot coverage, or maximum density permitted in accordance with any development standards contained in this Ordinance, the terms "land", "land area", "lot size", and "lot area" or any such similar term shall mean "developable land area", which is defined as follows: Developable Land Area is the total gross land area of the parcel proposed for development LESS the total of the following:
a) 
Freshwater wetlands as defined in Title 2, Chapter 1 of the General Laws of Rhode Island as amended and in any rules and regulations adopted pursuant thereto. Provided, however, that any setback requirement from the edge of a wetland as so defined in Title 2, Chapter 1, shall not be included in the calculation of wetland area.
b) 
Coastal shoreline systems as defined by Section 120.0-2A.1 of the Rhode Island Coastal Resources Management Program, as amended February 1982, or subsequent amendments thereto, as follows:
(1) 
Beaches and barrier beaches.
(2) 
Cliffs, ledges and bluffs.
(3) 
Coastal wetlands.
(4) 
Sand dunes.
(5) 
All directly associated contiguous areas which are necessary to preserve the integrity of such features.
c) 
Any public or private street or street right-of-way.
d) 
Existing water surfaces.
e) 
Areas required for stormwater retention/detention under this Ordinance, or any other Ordinance of the Town of Portsmouth, or by the RI Department of Environmental Management, or by the RI Coastal Resources Management Council.
f) 
Areas required for utility easements of public utilities.
5. 
No yard or lot legally existing at the time of passage of this Ordinance shall be reduced in dimension or area below the minimum requirements set forth herein. Yards or lots created after the effective date of this Ordinance shall meet at least the minimum requirements established by this Ordinance.
6. 
Corner lot. The front lot line of a corner lot shall be established by which lot line the front entrance to the building faces, or is proposed to face. Corner lots may deviate from this requirement if strict application would prevent any reasonable use of said lot. Burden shall be on the applicant to justify such deviations.
7. 
Density and coverage in multi-use situations. On any lot on which more than one (1) type of use is allowed, either as a matter of right or as a special use permit, the amount of land needed to meet the area or coverage requirements for one (1) use may not be used to meet the requirements of any other use. Where the ordinance may be interpreted in more than one (1) manner, that interpretation shall be used which results in the least intensive use of the land and the most open space.
8. 
Any land taken by eminent domain, or conveyed for a public purpose for which the land could have been taken or was taken by eminent domain, shall not be deemed to be transferred in violation of the land area, width and space provisions of this Ordinance.
Minimum Yard Setbacks
Maximum Bldg. Height
Zoning District
Min. Lot Size
Min. Lot Area per Dwelling Unit
Min. Lot Frontage
Front
Rear
Side
Stories
Feet
Max. % Lot Coverage
RESIDENTIAL DISTRICTS
R-10
10,000*
10,000**
100'
20'
20'
10'
2-1/2
35'
20%
R-20
20,000*
15,000**
110'
30'
30'
15'
2-1/2
35'
20%
R-30
30,000*
30,000**
125'
30'
30'
20'
2-1/2
35'
20%
R-40
40,000
40,000
125'
30'
30'
20'
2-1/2
35'
20%
R-60
60,000
60,000
200'
50'
50'
50'
2-1/2
35'
10%
COMMERCIAL DISTRICTS
C-1
20,000
110'
30'
20'
15'
2
35'
25%
TC-C
[Added 10-27-2004]
20,000
110'
5'
20'
15'
3
35'
35%
INDUSTRIAL DISTRICTS
I-L
40,000
200'
60'
50'
30'
2
35'
25%
I-H
40,000
200'
60'
50'
30'
2
35'
25%
WATERFRONT DISTRICTS
WD
20,000
15,000
110'
30'
30'
15'
2-1/2
35'
30%
*
Except 40,000 square feet where not serviced by a public water system
**
Where more than one dwelling unit is permitted on a lot.
1. 
Not less than the frontage requirements shall be maintained throughout the front yard depth, except as provided for in Section D.5 of this Article or by dimensional variance, and for Planned Unit Developments per the provisions of Article VIII.
[Amended 10-27-2004[1]]
[1]
Note: "and for Planned Unit Developments per the provisions of Article VIII" adopted 10-27-2004.
2. 
The required front, side and rear yards shall be unoccupied and unobstructed by buildings or structures, except as provided as follows:
a) 
Ordinary projections of window sills, cornices, eaves and other structural features may extend not more than eighteen inches (18") into the space above required yards:
b) 
Signs as permitted herein;
c) 
Driveways and walkways;
d) 
Fences as permitted herein;
e) 
Accessory uses and structures as permitted herein.
3. 
On lots abutting streets on more than one (1) side, the front yard requirements shall apply to each of the abutting streets.
4. 
A dwelling need not be set back more than the average of the setbacks of dwellings on the lots adjacent to either side. If a vacant lot exists on one (1) side, it shall be considered as a dwelling setback at the depth of the required front yard.
5. 
Storage sheds up to one hundred twenty square feet (120 ft.2) in area must be located in the rear yard and are permitted no closer than three feet (3') to rear and side lot lines. Storage sheds over one hundred twenty square feet (120 ft.2) in area must be located in the rear yard and meet all dimensional requirements of the district in which they are located.
6. 
On any lot which contains a development of a commercial nature there shall be a compact evergreen screen along any side or rear lot line which abuts a residential zone. The screening area shall be five feet (5') deep and the evergreen plants shall be at least six feet (6') in mature height. In place of said screening area, an opaque fence may be allowed as a special condition.
7. 
If more than one (1) building (other than a one (1), two (2), or three (3) car garage, a tool shed, a greenhouse or a cabana) is lawfully placed on any lot in single or common ownership, the distance between the nearest parts of such buildings shall be not less than twenty feet (20').
8. 
Open storage must provide front, side and rear yards as indicated by district.
9. 
Maximum Lot Coverage may be increased in the TC Zone and in Planned Unit Developments if off-site parking is provided per the provisions of Article IX. Section A.6. or 7. herein.
[Added 10-27-2004]
10. 
In all districts, off-street parking provided and maintained as paved/impervious surface shall be counted as part of the allowable lot coverage as defined and specified herein and in Articles VII, VIII and IX of these regulations. However, driveways to and parking areas for single and two-family residential uses, other than those listed in Article VII and VIII, shall not be counted toward lot coverage.
[Added 2-4-2008; amended 2-13-2012]
11. 
Parking areas composed of pervious surfaces are encouraged for all land uses and lots, unless there are overriding environmental limitations, and may be provided to meet part of any required parking spaces on a lot. Except for single and two-family residential uses, as above, twenty percent (20%) of such pervious surfaces which provide for grass surface shall be counted as part of the overall allowable lot coverage; otherwise sixty percent (60%) of such pervious surfaces shall be counted.
[Added 2-4-2008; amended 2-13-2012]
1. 
Height restrictions may be waived by the Board of Review for office buildings, Planned Unit Developments and motels subject to the following conditions:
[Amended 10-27-2004[1]]
Town Center
All Other Districts
Minimum land area
2 acres
5 acres
Minimum frontage
110 feet
300 feet
Minimum yard depths in addition to required yard depths; one foot (1') for each foot of height in excess of maximum allowed as a matter of right for the zoning district in which it is located.
Except fifty feet (50') when abutting a residential zone, and screening shall be provided.
[1]
Note: TC-C (Town Center Commercial) adopted for Planned Unit Developments per the provisions of Article VIII adopted 10-27-2004.
2. 
The following structures or parts of structures, when accessory to a permitted or special use permit principal use may be permitted above the maximum height limitations set forth herein, provided they meet all other rear lot, side lot and front lot requirements of this Ordinance:
Flagpoles, chimneys, radio masts, television antennas, water towers, skylights and other necessary features appurtenant to buildings which are usually carried above roofs and are not intended for human occupancy.
a) 
Wireless or broadcasting towers are not excepted herein, but are subject to a special use permit. (See also Article VII. Section E. for antennas over thirty-five feet (35') in height.)
3. 
Structures other than those listed in the paragraph above, may exceed the height limitation provided only upon the granting of a dimensional variance by the Zoning Board of Review.
4. 
For the purpose of side yard regulations, the following dwellings with common party walls shall be considered as one (1) building occupying one (1) lot: duplex dwellings and townhouse dwellings.
5. 
Irregular shaped lots are to receive special consideration by the Board in that lot frontage may be determined at a depth of thirty feet (30') radially opposite and concentric with the front boundary, providing that the front boundary line is not less than seventy-five feet (75') in length. This thirty foot (30') strip is to be excluded from the overall lot size requirement.
6. 
Side Yard and Rear Yard setbacks may be reduced, except where abutting residentially zoned parcels, in the Town Center District and in Planned Unit Developments, dependent upon the degree of fire protection and access, in consultation with the Fire Department.
[Added 10-27-2004]
Except as otherwise provided herein, on any lot on which more than one (1) type of use is allowed, either as a matter of right, a special use permit or a Planned Unit Development, the amount of land needed to meet the area or coverage requirements for one (1) use may not be used to meet the requirements of any other use. Where the ordinance may be interpreted in more than one (1) manner, that interpretation shall be used which results in the least intensive use of the land and the most open space.