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� <br /> #06-3240 B�sement&Story De�initions <br /> October 12,2006 . <br /> Page 3 <br /> The 2000 IBC defilies "story above grade plane" as: <br /> Story Above Gracie Pl1ne. Any story haviilg its finished floor slu�face entirely above <br /> grac�e plane, except tliat a baseiiient shall be considereci as a story above grade plane <br /> wliere the finislied surface of tlie flooi above the baseiiient is: <br /> 1. More than 6 feet above grade platze; <br /> � <br /> 2. More than 6 feet above the fiiiished ground level for more tlian 50% of the total <br /> buildiiig perinleter; or <br /> 3. More thaii 12 feet above the finished ground level at any point. , <br /> . ANALYSIS � <br /> • We have liot been following the defuution of basement in the zonitig code. <br /> - • We have not beeii following the defuution of basement in the 2000 IBC. <br /> • We have been adnuiustering the 2-1/2 story height limit.by defnung the baseinent via a <br /> "functional definition" thaf is fairly st�aightforward to deal with, but not supported by <br /> any codes, nor does it appea.r in our B&Z design i�ianual. The "functional defmition" <br /> we have beeii most recently using is as follows: <br /> The lower poi�tion of a building is considered as a basemeiit (and not a story) <br /> when at least 50% of the lowest poi�tion's perimeter is covered (b�pre-eaisting � <br /> ' grade, not filled finished •g�ade) to a height of at least 6 feet above the lowest <br /> floor (i.e. we nzeasrcre up from tlte lowest floor). The perinieter of the lower <br /> level does iiot include portions of the house or garage tliat do iiot have a lower <br /> level but are merely"unexcavated". <br /> • The IBC ineasa«•es �lowi:from th.e floor above, not up froiii the lowest floor. For <br /> example, for a lower level tliat is 10 feet fronl top surface of `lowest floor' to top <br /> stuface of `�lie floor above the basement' (call iliis the `next floor'), the IBC says the <br /> lower level is a storv, not a baseiilent,if any one of the followiiig situations exist: <br /> a) the `next floor' is more than 6' above the "grade plane" [so we would measiue <br /> the exposed wall from avera�e finished rade to the `ilext floor', whicli meaus <br /> we have to deterinine the elevatioii of tlie "grade plaiie", �uid conipare it to the <br /> , elevatioii of fhe `next floor']; or � <br />