When trying to cover vehicles and RV's we always want to utilize the height as best we can. Often customers will order an RV Cover much too tall, basing the height on the tallest point of their RV or Trailer. With this in mind we like to explain how the height is determied on our metal buildings. As a basic rule our standard pitch on all our buildings is 3/12, this means you will gain 3" in height for every 12" in width. When pricing and planning keep in mind we measure at the leg height, not the peak height. A 12x30x12 Carport will have a 12' Leg, and will gain additional usable height to the peak. Let's take for example an RV with an AC reaching to 12'6". On the original 12x30x12 RV Cover we are discussing, you will gain approximately 18" to your peak, not counting framing. This willl put you at roughly 13'6" at your peak, and making this a reasonable height for your new RV Cover. There are some exceptions to this rule, based on different roof styles (Regular/Standard gains a little more height and why this style is commonly used for RV and Trailer Covers) and custom pitchs. It's always encouraged to speak with your sales person about the size of the RV, Trailer or Car you are trying to cover.