13-200-230 Increase in one additional dwelling unit.

   In any residential building or building of mixed occupancy, with one of the occupancies being residential, the number of dwelling units may be increased by one dwelling unit above the number of legally established dwelling units providing the building complies with the following requirements:

   (a)   The alterations meet the requirements of Title 17 of this Code;

   (b)   The building shall not be more than four stories high for ordinary construction (Types III-B or III-C), and not more than two stories high for combustible frame construction (Types IV-A or IV-B). Buildings of mixed ordinary and frame construction shall be governed by the requirements of combustible frame construction;

   (c)   A basement may be used for habitable rooms or a dwelling unit, regardless of the depth of the floor below grade, if the floors and walls are impervious to leakage of underground and surface runoff water and are protected against dampness, and if the required minimum window area is located entirely above the finished elevation of the ground adjoining the building wall in which the windows are located;

   (d)   Area and space requirements of Sections 13-196-470 through and including 13-196-490 shall be met in all rooms, except that at least 80 percent of the floor area of every habitable room shall have a ceiling height of not less than seven feet, six inches. Twenty percent of the floor area of any habitable room may have a ceiling height as low as six feet, eight inches;

   (e)   Natural Light and ventilation shall comply with requirements of Chapter 13-172;

   (f)   Exits shall comply with the exit requirements of Sections 13-200-330 through and including 13-200-360, except that basement dwelling units may have a second exit through a space containing a heating plant;

   An existing building or structure may be increased in height or area up to the limits imposed by Chapter 13-48.

   (g)   If the basement contains a dwelling unit, the entire basement ceiling construction shall be one-half hour rated construction, or the original wood lath and plaster construction;

   (h)   Basement apartments shall be separated from heating plants as required by Section 15-8-190;

   (i)   Any subsequent or additional increase of one unit or more under this provision shall meet the requirements of Section 13-200-240.

(Prior code § 78.1-22; Amend Coun. J. 10-28-87, p. 5549; Amend Coun. J. 6-14-95, p. 2841; Amend Coun. J. 4-29-98, p. 66679, § 2)

 

Notes

Title 17

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13-200-240 Increase of two or more dwelling units.

   In any residential building or building of mixed occupancy with one of the occupancies being residential, the number of dwelling units may be increased by more than one dwelling unit above the number of legally established dwelling units providing the building complies with all of the requirements listed in Section 13-200-230, and also the following additional requirements:

   (a)   Stairways shall be enclosed with walls of one hour construction in buildings not exceeding three stories in height. Stairways shall be enclosed with walls of two hour construction if the building exceeds three stories in height. Stairwell enclosures may be combustible or noncombustible construction as long as the required separation ratings are met.

   (b)   Stairwell doors shall be one and three-fourths inches solid-core wood with one and three-fourths inches rabbeted wood frames in buildings not exceeding three stories in height. Stairwell doors shall be Class B and frames in buildings exceeding three stories in height. All stair doors shall be self-closing.

   (c)   All existing dwelling and corridor separations shall be one-half-hour rated construction, combustible or noncombustible. All new dwelling and corridor separations shall be one hour rated construction, combustible, or noncombustible.

   (d)   Corridor doors to dwelling units shall be one and three-fourths inches solid core wood with one and three-fourths inches rabbeted wood frames. All corridor doors to dwelling units shall be self-closing.

   (e)   Heating plant enclosures shall comply with the requirements of Section 15-8-190.

   (f)   Basement ceilings shall comply with the requirements of Section 13-60-200.

(Prior code § 78.1-23; Amend Coun. J. 10-28-87, p. 5549)

13-200-250 Additions.

   An existing building or structure may be increased in height or area up to the limits imposed by Chapter 13-48.

   (a)   When the floor area is increased by not more than 25 percent of the original building, only the new construction need conform to all requirements of this Code for new construction. When the floor area is increased by more than 25 percent of the original building, the entire building shall conform to all requirements of this Code.

   (b)   Where a fire wall complying with Chapter 15-8 is provided which separates the addition from the existing building, only the new construction need conform to all requirements of this Code for new construction, regardless of the percentage increase in area created by the addition. Such an addition with the required fire wall separation, may also be considered a separate building if on a separate lot.

   (c)   No addition shall impose exiting loads which exceed the capacity of the existing building exits without provision of additional exits, in conformance with Section 13-200-330 through and including 13-200-360 of this chapter for the existing building or Chapter 13-160 for the addition.

   (d)   No addition shall impose structural loads, either vertical or horizontal, which would cause the existing building to be subjected to stresses exceeding those permitted by the new construction. Any increase in floor or roof loading shall be investigated to determine the adequacy of the existing floor system to support the increased loads. If the existing floor system is found to be inadequate, it shall be modified to support the increased loads.

(Prior code § 78.1-24; Amend Coun. J. 2-13-85, p. 13525)

13-200-260 Porches and decks.

   Existing porches and decks may be repaired or replaced in the same location with construction of the same type as that of the existing porch or deck.

   (1)   Existing porches not exceeding three stories in height may be extended up one story to the roof level regardless of their location with respect to the lot line or other buildings on the same lot, if in conformance with the zoning ordinance.

   (2)   Existing porches may be enclosed, regardless of their location with respect to the lot line or other buildings on the same lot, if construction requirements of Chapter 13-60 are met. If the existing porch is less than six feet from an interior lot line, the enclosure shall be a minimum of one hour rated construction, if in conformance with the zoning ordinance.

   (3)   Replacement porches shall be designed to meet all load criteria for new construction.

(Prior code § 78.1-25; Amend Coun. J. 10-1-03, p. 9163, § 4.12)

13-200-270 Dormers.

   Dormers may be added to any residential building provided that zoning requirements and the following requirements are met.

   (a)   If dormers are added to an attic space which is part of the apartment below it, the attic floor shall not be considered an additional floor in terms of building height if all of the following apply:

      (1)   The total and dormered area does not exceed two-thirds of the floor area of the same dwelling unit on the floor immediately below, when counting all areas with a headroom of five feet or higher;

      (2)   The dormer addition does not exceed the height of the existing building ridge line or the maximum building height permitted by Table 13-48-030, whichever is higher;

      (3)   The existing roof configuration has not been altered along the street lot line and the street- facing dormer wall is held back at least 24 inches from the face of the wall below;

      (4)   The number of living levels, as defined in Section 13-4-010, shall not exceed three levels in Type II-C, IV-A and IV-B buildings, or four floors in Type III-B buildings.

   (b)   Along interior lot lines, dormers may be built with their outer wall flush with the existing wall below, provided, however, such construction complies with the Zoning Ordinance.

   (c)   Dormers built on a building of ordinary construction (Type III-B or III-C) may be built of one hour metal stud or fire retardant treated wood in lieu of masonry, provided it meets the applicable construction requirements of Chapter 13-60 and does not exceed the height and area limitations of Chapter 13-48.

   (d)   Dormers built on a building of combustible frame construction (Type IV-A and IV-B) may be built of wood frame construction, provided it meets the applicable construction requirements of Chapter 13-60 and does not exceed the height and area limitations of Chapter 13-48.

(Prior code § 78.1-26; Amend Coun. J. 10-2-95, p. 8040)

13-200-280 Skylights.

   Prefabricated standard acrylic or polycarbonate skylight units may be installed in existing buildings not exceeding ten percent of the total roof area. In addition, custom built skylights may be installed in existing buildings if their frames are constructed of noncombustible material and if they are glazed with laminated glass or other approved safety glazing materials.

(Prior code § 78.1-27)

13-200-290 Utilization of existing space within residential buildings.

   Utilization and finishing of basement and attic space, including dormer additions, which make productive use of the existing floor area, and which become part of an existing dwelling unit but are not used to create additional units, shall not be considered as additional stories for purposes of height limitations under the code. However, the number of living levels, exclusive of the basement, is not to exceed three levels in Type IV-A and IV-B buildings, and four levels in Type III-B and III-C buildings.

(Prior code § 78.1-28)