Ideally, you need 12” headroom for installing commercial roll up doors. This is the required minimum clearance, so you can have more but not less than 12” of headspace. The head clearance must be measured accurately from the header opening to the ceiling or any other vertical encumbrance, such as ledges or fur downs. Note that some doors can require a minimum clearance of 16”, so it’s better to consult a professional door installer.