A. Maximum Gross Floor Area: No building or any of its accessory structures and uses shall be erected, constructed, or altered on any lot in any residential district if, as a result of such erection, construction, or alteration, the gross floor area of such lot exceeds the maximum gross floor area permitted for that lot as determined by the following applicable computation:
1. The maximum gross floor area for any lot of less than or equal to nine thousand (9,000) square feet shall be computed as follows:
0.4 x lot size in square feet
2. The maximum gross floor area for any lot of more than nine thousand (9,000) square feet, but less than or equal to eighteen thousand (18,000) square feet, shall be computed as follows:
3,600 + (0.2 x total square feet of lot size in excess of 9,000)
3. The maximum gross floor area for any lot of more than eighteen thousand (18,000) square feet shall be computed as follows:
5,400 + (0.1 x total square feet of lot size in excess of 18,000)
B. Special Gross Floor Area Calculations And Exceptions: For purposes of determining the maximum gross floor area permitted for a lot, the following special calculations and exceptions shall apply:
1. Underground Structures: Except as otherwise provided in section 10-12-8 of this title, the following shall be included in the calculation of the gross floor area of a lot:
a. Basements, Crawl Spaces, And Subterranean Garages:
(1) For a basement, crawl space, or subterranean garage constructed on or after January 1, 1950, the total area, in square feet, of all of that portion of such structure that extends three feet (3') or more from the preexisting or proposed grade, whichever grade is more restrictive, to the finished first floor elevation (see section 10-13-1 of this title, illustration 19).
(2) For a basement, crawl space, or subterranean garage constructed before January 1, 1950, the total area, in square feet, of all of that portion of such structure that extends five feet (5') or more from the preexisting or proposed grade, whichever grade is more restrictive, to the finished first floor elevation (see section 10-13-1 of this title, illustration 20). If, however, the principal structure is structurally altered, enlarged, or replaced to the extent of more than fifty percent (50%) of the floor area of the principal structure existing at the time of such alteration, enlargement, or replacement, the special gross floor area exception contained in this subsection B1a(2) shall no longer apply.
b. Expanded Window Well: The total area, in square feet of the expanded window well, calculated by taking the ratio of the length of the exposed basement wall within the window well that is three feet (3') or more in height (measured from the bottom of the well to the finished first floor elevation) to the total perimeter of the foundation of the structure, and multiplying that result by the total floor area of the basement and/or crawl space (see section 10-13-1 of this title, illustration 20).
c. Walkout Basement Stairwell: The total area, in square feet, of the walkout basement stairwell, calculated by taking the ratio of the length of the exposed basement wall within the basement stairwell that is three feet (3') or more in height (measured down from the first floor elevation) to the total perimeter of the foundation of the structure, and multiplying that result by the total floor area of the basement and/or crawl space (see section 10-13-1 of this title, illustration 20).
2. Accessory Structures: For any conforming accessory structure within the rear twenty five percent (25%) of the lot on which it is located or entirely within the rear twenty seven feet (27') of any such lot, whichever is greater (the "qualified accessory structure"), the following special regulations shall apply to determine the gross floor area of the lot. The provisions of this subsection B2 shall not apply to through lots. For purposes of this subsection B2 only, a lot that is both a corner lot and a through lot shall be considered a through lot.
a. Lots Six Thousand Two Hundred Fifty Square Feet And Less: The first four hundred forty (440) square feet of any qualified accessory structure on any lot is six thousand two hundred fifty (6,250) square feet or less in total area shall not be included in the gross floor area of the lot on which such structure is located.
b. Lots Greater Than Six Thousand Two Hundred Fifty To Eight Thousand Seven Hundred Fifty Square Feet: For any lot with an area greater than six thousand two hundred fifty (6,250) square feet but less than or equal to eight thousand seven hundred fifty (8,750) square feet, the amount of the qualified accessory structure that shall not be included in the gross floor area of the lot on which such structure is located shall be determined according to the following formula:
[440 - ((lot size - 6,250) x 0.176 square feet)]
c. Lots Greater Than Eight Thousand Seven Hundred Fifty Square Feet: The gross floor area of any accessory structure on any lot in excess of eight thousand seven hundred fifty (8,750) square feet shall be determined pursuant to the otherwise applicable provisions of this title.
d. Drainage Plan Approval:
(1) No qualified accessory structure or portion thereof shall be excluded from the gross floor area of a lot pursuant to the provisions of this subsection, unless in compliance with the following conditions:
(A) Submittal to and subsequent approval by the village engineer of a drainage plan demonstrating that all stormwater runoff from the garage roof and driveway can either flow overland directly to a public right of way without flowing across an adjacent private lot, or flow through a recorded drainage easement across adjacent private property in order to discharge into a public right of way; or
(B) Submittal to and approval by the village engineer of a drainage plan demonstrating that any portion of stormwater runoff from the garage roof and driveway, which does not flow directly to a public right of way without flowing across an adjacent private lot(s), or does not flow through a recorded drainage easement, will be directed to a stormwater detention facility within the limits of the subject lot; such detention facility shall be capable of providing storage for the volume of rainfall generated by the maximum anticipated twelve (12) hour duration, 5-year rain event per the latest revision of IDNR/OWR bulletin 70, and subsequent pumped discharge to a public right of way in a manner acceptable to the village engineer.
(2) Implementation of a stormwater detention facility shall include requirements recorded against the lot that the detention facility be maintained in operating condition at all times.
3. Stoops And Decks: That portion of stoops and decks in the rear or side yard with: a) a floor elevation of less than thirty inches (30") above grade; b) open type railings or surrounding appurtenances less than forty two inches (42") in height, where the visibility at right angles to the surface is not reduced by more than thirty percent (30%), or no railings or surrounding appurtenances; and c) an area of less than three and one-half percent (3.5%) of the total area of the lot on which the stoop or deck is located, shall not be included in the gross floor area of the lot. Such exclusion shall also include the steps, if any, leading to any such stoop or deck that satisfies the requirements of this subsection.
4. Covered Outdoor Porches, Open Entryways, Open Covered Walks And Uncovered Exterior Balconies:
a. A portion of covered outdoor porches, open entryways, open covered walks, and uncovered exterior balconies may be excluded from the gross floor area of a lot; provided, that the total exclusion for all such structures shall not exceed the lesser of: 1) three and one-half percent (3.5%) of the total lot area; or 2) five hundred (500) square feet; and provided further, that:
(1) The covered outdoor porch:
(A) Is constructed with no railings or with open railings that are no more than forty two inches (42") in height, where the visibility at right angles to the surface of the open railings is not reduced by more than thirty percent (30%). In addition, the area above the open railings, or where there are no railings, the area above the floor, shall be open except for: 1) screens; 2) necessary primary vertical structure elements that do not exceed twelve percent (12%) of the area above the open railings; and 3) decorative, architectural lattice elements located along the top eighteen inches (18") of the covered open porch (see section 10-13-1 of this title, illustration 18); and
(B) Has no floor area or exterior balcony located directly above such porch (see section 10-13-1 of this title, illustration 12).
(2) The uncovered exterior balcony is constructed with open railings that are no more than forty two inches (42") in height, where the visibility at right angles to the surface is not reduced by more than thirty percent (30%) (see section 10-13-1 of this title, illustration 18).
b. Such exclusion shall also include the steps, if any, leading to any such covered outdoor porch, open entryway, or open covered walk that satisfies the requirements of this subsection.
5. Space In Excess Of Ten Feet In Height: The floor area of any space with a floor to ceiling height in excess of ten feet (10') shall be increased by ten percent (10%) for each foot, or fraction thereof, in excess of ten feet (10'). For purposes of this subsection, in the case of a sloping or slanting ceiling, only that area under a plane that is: a) parallel to, and most distant from, the floor below it; and b) at right angles with the adjacent exterior wall or walls, shall be included in the additional floor area calculation. (See section 10-13-1 of this title, illustration 13.)
6. Undereaves: The footprint of eaves areas under sloping roofs that extend no more than two feet (2') from any adjacent exterior wall shall not be included in the gross floor area of the lot.
7. Attics: Only that portion of an attic floor that: a) has a floor to ceiling height equal to or greater than six feet (6'); and b) is determined by the village building commissioner to have been designed to be readily utilized for, or readily converted to, eating, sleeping, or living areas, shall be included in the gross floor area of the lot. In making such determination, the building commissioner shall consider such factors as, without limitation, the method of access and emergency egress, natural light and ventilation provided for such space, and the size of such space.
8. Flag Lots: The "pole" portion of any flag lot shall not be included in the lot size calculation used to determine the maximum permitted floor area. On lots other than flag lots that consist of: a) a primary mass at least fifty percent (50%) of the total area of the lot and set back from the street frontage access ("the primary portion"); and b) a narrow access corridor with a width of no more than fifty feet (50') wide and a depth to width ratio of no more than three to one (3:1), only the primary portion shall be included in the lot size calculation to determine the maximum permitted floor area. (Ord. 94-2, 2-15-1994; amd. Ord. 98-6, 2-23-1998; Ord. 2000-11, 7-11-2000; Ord. 2005-1, 1-10-2005)