I am buying a 8'x12' prefabricated wood shed (6' sidewalls) and putting it onto an approximately 9'x20' 3" thick concete slab that is currently used as a parking space. From everything I've heard from shed dealers, these are not usually anchored down in residential applications, but our fire marshal wants it securely anchored since this is a commercial property. On each side of the concrete slab, there is grass. I was thinking of anchoring the shed with large angle brackets, with tapcon-style anchors in the concrete and wood or drywall screws on the shed side. Would this be a secure way to mount the shed? How many angle brackets would I need for a secure installation? Would 10 (3 on each long side, 2 on each short side) be overkill? I want to do what is required, but keep the costs down if possible. Does anyone have any other suggestions other than the angle brackets? Thanks ahead of time for the help.