The outside is coated with five gallons or more of Epoxy, from Sherwin Williams, Called "cold tar epoxy" Same as used and approved by the U.S. Corps of Engineers for use on salt water drilling rigs, underground gas storage tanks, under coating of barges, and even dam gates! It's a very hi-mil coating that we spray on with a hydraulic pump spray rig. Top, bottom, everywhere! .
Inside is finished with Sher-Kem gloss white. Three coats. A direct to metal chemical/paint from Sherwin Williams. Used for heavy equipment coating. Same paint as used on commercial jet air craft outside.
The door is 32" x 57". Standard height in center dome is about 6'5". Top of dome to door lip is 6" to 8". Can be extended. Seat width 14". Seat height about 16" so you can store under the seats. Turbine vent 14", can be altered. All shelters can be made to go deeper in the ground, up to 20" at the center dome.
The floor is 10ga, main unit 12ga, and standard door 14ga. All sizes have channel/angle iron reinforcements added. Across sides, floor, roof, and back. Extremely heavy duty built. Latches, single throw 1/2" in 3 places. Three Heavy Duty hinges. Lockable outside handle.
The standard door has been tested by a REAL EF5 tornado. Not just lab tested. Plus we feel, shooting a 15lb. 2x4 at 100mph is not a true test. Tornados throw whole trees, cars, tractors, and other people's houses at you.