10-16-2006 Planning Commission Packet

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#06-3240 B�sement&Story DeCnitions October 12,2006 . . P�ge 4 � b) the `neat floor' is more tllan 6 feet above the finished ground level for at least 50% of the total buildiii�perinieter [so we ineasure the exposed wall below tlze `neat floor' for the whole builcling (? or for just that part with a lower level?) and if the exposed wall is more than 6' for more thaii 50% of the perimeter, the � basement is really a story]; or . c) tlie `next floor' is more than 12 feet above finislied grade at any point. Finished Grade vs Pre-Existing Grade � Uiitil perliaps a year ago, we allowed the 6' basemeiit wall coverage required Uy our fiulctional definition,to be met by ai-tificially filling against tlie foundation. The result was that on certain Iots, builders n�ight liave just oiie corner of a house meetiilg tlle 6' foundation coverage . naf�irally, then piliiig dii�t up against other foundation walls to get to a 50%perimeter coverage . of 6'. Piling fill against the founclation and leaving it at a steep slope resulted in an i.uuiat�iral artificially fu�islied a�pearance, and in the case where retaining walls were added 5-10' out from the foundation to retaiii the fill,the baseinent fioin a distance looked like a story. We then revised our functional defiiutioil to require that tlie 6' coverage must be based on pre- existing grades, not artificially raised grades, based on the existing definition of building height ` "' that disallows "topograpluc changes wluch elevate the adjoining ground level above the � existing terrain". Since tlus cliange, probably half of tlie building plans that have come before us lZave had to be revised to ineet tlus standard, because most holnes beiiig btiilt today have tUree full levels - if the baseiilent is a story, then they have a 3-story home not iileeting the 2- 1/2 story limit. Average Elevation vs Grade Plane , . Both the zoning code and 2000 TBC definitioils relate to an `average grade' concept, related to fiiushed grade, but measure it differeiitly: . - the zoning code nleasures it as the avera�e elevation of the finished ground surface . witlun 5 feet of the foundation; - the IBC measures fihe "grade plaile" as the average of fmished �ground level adjoiiung . � the exterior walls. Where the grade slopes away froin the building, the reference points to be used in determining tlie average fiiushed ground level are tlze lowest points of the finished ground surface within 6 feet of ihe buildiiig. We have concluded that "average elevation" caiuiot be simply the average of the liighest aiid lowest elevatioiis that the foundation abuis; it llas to be a weighted average based oii�lie entire perinleter. This, coupled with haviiig to deterniiiie final (or pre-existing) grades at some distlnce of 5-6' out froin tlie foundation, adds com�lexity to the deteriniiiatioil of whether a level is a baseinent or a story.