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, , <br /> Floodplain Information Sheet 4 <br /> M����� Floodplain Management Series <br /> iBasement & Lowest Floors for Homes in a Floodplain <br /> o�um�Ma <br /> ',NATUFRI PESOUACES <br /> ___ _- _.. ___. _ - __-.__ __. � <br /> i� <br /> Related Definitions <br /> Determining the "lowest floor" of a structure in a floodplain <br /> is important because the top (i.e.,walking surface� of the lowest Lowest Floor–Lowest floor of the lowest enclosed ' <br /> floor must be at or above the Regulatory Flood Protectton area(including basement or crawl space).The � <br /> Elevation (RFPE). Lowest floors include basements and crawl lowest floor level must meet minimum elevarion <br /> ; requirements (i.e.,the Regulatory Flood Protection <br /> spaces of any size. An improperly elevated lowest floor can ' Ele�ation). <br /> result in a significant increase in flood insurance premiums!! ' � <br /> , Basement–�1ny area of a structure,including crawl '; <br /> space,having its floor subgrade(below ground <br /> level)on a11 sides. <br /> �owest Upper level Regulatory Flood Protection Elevation(RFPE� i <br /> The RFPE is the 100-year flood(1 percent annual i <br /> Adjacent <br /> �rede chance flood)elevation+ stage increase due to es- <br /> Lowest Level Garage tablishing floodway+ freeboard(Nlinnesota's mini- <br /> R F P E � � � ' mum is 1 foot). The lowest floor must be elevated I <br /> � so that the walking surface of that lowest floor is at � <br /> Fill <br /> Natural So�i the RFPE or higher. II <br /> Top of lowest level floor is lowest floor Base Flood Elevation(BFE)Same as the 1 percent I <br /> Figure 1.A concrete slab on grade is permitted for a annual chance Aood elevadon or the"100-year" ; <br /> home in a floodplain if the top(walking surface)of the flood elevation. <br /> lowest level floor is above the RFPE. �— <br /> The floodplain regulations apply to all enclosed spaces; they ' RFPE Formula ' <br /> do not differentiate between finished versus unfinished, habit- 100-year flood elevation <br /> + stage increase due to floodway i <br /> able versus not habitable,or a space that is more than a certain +freeboard (state requires 1-foot minimum) ' <br /> minimum height versus a space that is only a couple feet high. ; = regulatory flood protection elevation (RFPE) ' <br /> �owest <br /> Adjacent lovrest <br /> Grade Adjacen <br /> Main Garage ��� Main <br /> RFPE Level 't � � �evel � �� �?,�>��e <br /> � �� � <br /> �FE � "�',,,� �, �� � Crar�rt5par. .,� .e.. I FE <br /> '�asem � <br /> Fill �=�'r�a«rat sa� Fill ra a�ara�s oii <br /> Top of craavl space flaor is lowest floor <br /> Top af basemerrt floor is 6owest floar <br /> Figure 2. This example is not permitted for a home Figure 3.A below grade crawl space or utility space is <br /> in a floodplain because the basement is the lowesf considered a basement and it is the lowest floor. It is <br /> level of the home and it is below the RFPE. not permitted for a home in a floodplain because it is <br /> below the RFPE. <br /> Myths and Facts of Basement Definitions <br /> Myth: It is not a basement if I cannot stand up in it. <br /> Fact: It does not matter if a basement is 2 feet or 8 feet high, or if it is "habitable"based on state building code. <br /> ', It is a basement if it is below gxade on all sides. <br /> j Myth: It is not a basement if the floor is unfinished or dirt. <br /> � �I Fact: It does not matter if a basement floor is concrete or unfinished. It is a basement if it is below grade on all sides. <br /> Contact: DNR Waters in St.Paul(651)259-5700 � Page�l <br /> http://mndnr.gov/waters August 2010 <br />