There are two major sets of factors that will influence the design and construction of your building. One is practical: the actual use of the building. If you're building a shed or garage, your needs may be as simple as an overhead door and a window; if you're using steel construction for your home, you'll need to include plumbing, wiring, and ventilation in your plans. (Note that all these subsystems need to be installed by the construction team you hire - they are not included in the price of the building itself.)

The second is legal. Every state has different building codes that will apply to your project. These will include things like snow load and wind load: how much of either your building must be able to stand up to. Other legal requirements include local zoning laws, drainage requirements, and more.

While steel building suppliers can often help you research these codes - most won't ship you a building that doesn't meet codes in your area - the ultimate responsibility for meeting them is yours. The bottom line on planning your building is that if you're not familiar with major construction projects, you'll need to rely on experts to assist your planning.

Types of steel buildings
There are two main types of steel buildings to choose from. Arch style steel buildings (aka Quonset huts) became popular during World War II. They are built from a series of interlocking metal ribs that form the roof and sides of the building. Residential arch buildings are popular for garages and sheds because their construction methods are simple and they are less expensive per square foot. They are not very adaptable or customizable, however. Their construction only allows for doors and windows in the endwalls, not the sides, and the overhead clearance drops considerably as you get further away from the center of the building.

If you're building a home, you'll want to choose a rigid frame style building. These are constructed with steel skeleton framing and flat steel panels for the roof and walls. They can include doors and windows in any wall, and can be expanded with relative ease. While they are still much easier to build than traditional buildings, more expertise and equipment is required to construct a rigid frame building than an arch style building.

Extras
Unless your metal building is going to be an unoccupied storage building, you will need insulation. The same rating system used in traditional construction is used for steel buildings: R-7 is equivalent to 2" of insulation, and R-19 is 6". Because steel is a very efficient conductor of heat, the need for insulation is greater in a steel building than a wooden frame building.

It's a simple decision: if you're going to be heating and cooling the building year round, you'll save money by buying R-19 insulation. Even though it is more expensive initially, the savings in your energy bill will easily make up for the cost in just a year or two. You may also want a vapor barrier for the roof and walls, which can prevent condensation.

Other important extras include doors for people and vehicles, windows and skylights, and gutters and downspouts to manage runoff. Be sure to inquire about the insulation value of the doors and windows: look for double-pane glass and insulated doors.

The final set of add-ons for your building are cosmetic. At a minimum, you'll be able to choose the exterior color of your building. For a home, you'll probably want to choose a cosmetic finishing option such as wood, brick, or stucco. These options are expensive but really make your house look like a home.