Gambrel buildings are often used for a gambrel shed, just being a smaller size an 8 x 10 or 10 x 12 are good size examples the 10 x12 is a popular choice for size for any type back yard storage building because they often don’t need a building permit.
A shed is kind of a catch all word used to describe about any kind of smaller type outbuilding, used for about anything from a tool shed, garden shed, lawn shed or sometimes just kind of a catch all shed..
Having a gambrel roof on a backyard type shed is a useful option and has a nice mini barn type look.. but not really to much advantage at all for any extra usable loft area, but in a 10 foot wide gambrel roof area you can add a higher shelf big type loft area
The 8 foot wide type gambrel shed won’t have any loft area at all, but you can use 4 foot high walls to help keep cost lower which would use only one 4 x 8 sheet of siding cut in half can for each side and just two of the same 4 x 8 types of siding for the front and the back of the building or it could be built all around a little taller and the same amount of siding by using 4 x 9 sheets the same way, and the building size can be laid out right on the siding
A 10 x 12 Gambrel Shed needs only about 5 or 6 foot walls.. to help keep the total building height down and to also help keep the building in proportion which will then make the gambrel shed about 11 to 12 feet tall. for 4×8 over lap type siding to be used it is helpful to have a siding seam in the center of the building, so the door cutouts can be used for the door material for the double doors of the Gambrel Shed