new doors come with 1.25" added to bottom of frame this to accommodate 3/4" flooring (carpet,wood,tile,etc.) that plus should always have air flow under door no less than 5/8" i prefer 3/4" plus the door 6'-8" plus jamb that makes 82 1/4" the doors i have been getting from lumber yard i have to make my door r/o 83 inch.the only thing i see wrong they only use single 2x for header we use 2 to ensure a proper place for casing we use a lot of 3.5 wide and will not fall on single
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