Billboard dimensions depend on the size and make of the mounting structure that will support it. Moreover, it also depends on the kind of material the billboard is made of. Here are common factors that affect the measurements of billboards.
Wooden Support Structure
Some ad and promotional signs are still supported with wooden frames, like in small construction sites or in the countryside. The effective and safe billboard dimensions should be 10 by 15 feet. Some attempt bigger sizes by constructing bigger wooden structures, but this sometimes mar the ad potential of a billboard. With time the sign board material sags with too many nailed or seamed joints. Moreover, big wooden structures easily weaken and thus are dangerous.
Steel Support Structure
Frames of steel are better and safer. Billboard dimensions can go as big as 20 feet by 30 feet. Some even as big as 40 by 50 feet or 60 by 40 feet. Free standing structures are safer than those mounted on building tops or sides. Frames on roof decks for huge measurements of billboards are susceptible to wind forces and seismic movements. Even the building where the frame is hoisted stands compromised during natural catastrophes.
GI Sheet Sign Material
Most billboard materials are GI sheets. They are joined together at their sides to form a big surface. Formerly, they were hand-painted with ads and promotions. Today, they are applied with adhesive canvas materials on which ad images are printed with a special jet ink. The adhesive materials come in 15 by 20 feet or 10 by 30 feet. Thus, a whole ad image is printed by dividing it into several sections. For billboard dimensions of 30 by 20 feet, the ad image may be split into two 15 by 20 feet sheets or two 10 by 30 feet images. Then, they are joined to form a whole image on the GI sheet surface.
Canvas or Tarpaulin Sign Material
With tarpaulin or canvas as billboard materials, measurements of billboards can go extra large sizes. Some tarpaulin or panaflex materials measure in 16 by 8 feet sections. Images are printed onto these sizes and then sewed and seamed to make a whole. For a size 45 feet by 16 feet, the image will be printed on five 8 x 16 feet sections (45 divided by 8 is 5). Afterward, the sections will be sewed together and seamed to produce the entire image.
A breakthrough in billboard technology enables printing of a whole image onto a whole seamless canvas. Not anymore in sections.
Generally, billboard dimensions are dictated by applicable local laws.