Steel Building Planning Guide
What Kind of Planning Needs to be Done?
It is usually wise to plan on purchasing a building larger than you initially think you might need – you WILL grow into the extra space! A good rule of thumb is to go one size larger so that future requirements can be accommodated without having to do an extensive remodel. Standard dimensions are calculated in increments of 10 feet, e.g., 20’ x 30’ or 60 feet by 100 feet. Custom sizes can be created, but that would significantly increase the cost. Some of the most common standard steel building sizes include: 30x40, 60x40, 50x100 and 60x120.
Community buildings generally have heights that vary, while standard heights of single- and multi-story buildings are usually governed by local code. As a rule, building eave height must be at least two feet taller than the highest framed opening (see below).
Based on the type and style of the building along with its proposed use, you can calculate the roof height. For example, aircraft hangars need to use the clear span style with high roof structures. Churches may need high vaulted ceilings to give a feeling of loftiness. With business offices, standard roof height is usually sufficient.
The shape of the roof can be designed based on the amount of clear space required in the middle of the room. Roof slope is expressed by the “roof pitch ratio” which is the number of inches of rise in 12 inches of horizontal length—with a colon between the two numbers. For example, a roof with a pitch of 2:12 (“two in twelve”) means that it slopes up two inches for every 12 inches of length (or two feet for every 12 feet of length).
A basic metal building has a roof pitch of 1:12, a nearly flat roof. Gabled buildings typically have a roof pitch ratio of 4:12. Higher-pitched roofs provide more cubic footage of space for a slight increase in cost. They are beneficial if you can utilize the space above the eaves. On the other hand, low-pitched roofs allow you to heat and cool the space more efficiently. Snow load is another consideration if your building will be in an area with significant snowfall. A steeper roof pitch will shed snow better.
A “framed opening” is term used to describe any opening in the building, covered by a door or not, which is larger than a “walk-door” (a door which people go through). They are generally large openings through which vehicles, large equipment, and loading items pass through. A garage doorway would be considered a framed opening, for example. Schools, retail stores, and manufacturing facilities often have a loading bay area, closed off by a massive door, which trucks can back up to in order to deliver or pick up large or a great number of items.