If you need wide open spaces inside your building, you’re going to want a clear span design.Clear span metal frame buildings are typically used for:
- Athletic facilities
- Agricultural buildings
Anytime you need a covered space with no columns cluttering up the inside, clear span (also known as steel span) is for you.
What is clear span?
Clear span construction is designed as a rigid frame that has high strength and durability. Steel is both. The frame requires no interior supports, resulting in an extremely versatile and economical building.
With no need for interior bracing or columns, it’s easy to partition off sections for various uses, easily rearrange them if needed, or just leave it as open space.
If you go inside a building constructed early in the 20th century, you would see the support columns lining the area. A good architect could simply incorporate them into the design of the space, but when it came time to modernize or update the building, those columns could be in the way.
One example is St. Peter’s Cathedral in Lafayette, LA. Some of the pews are right behind or up against a support pillar, with poor sight-lines and uncomfortable seating. It is a wonderful, old, historic church but when they needed to expand for a larger parish, the columns were not easy to work around and they couldn’t be moved.
Pricing for clear span construction
Like any steel construction, clear span is more cost-effective than other building materials with the added perk of going without interior supports. However, after a certain size-limit, the price does begin to increase, usually at about 150 feet wide.
After 150 feet, the frame must become proportionally heavier to bear the greater load. More materials mean more money. Still, if you converted to wood or stone, the weight and expense would be even greater.
How to measure for clear span framing
- Frame width - To get the right frame width, measure between the outside surfaces of the girts or the outside of the eave struts. The girts are the stabilizing horizontal beams that run between columns. Wall panels are fastened to the girts. Eave struts are similar cross beams at the top of the wall beneath the edge of the roof.
- Clear span - Measure the distance between the inside faces of the columns along the walls to either side of the clear space.
- Eave height - Measure between the bottom of the base place of a wall column and the top of the eave strut.
- Clear height - Measure the distance between the floor and the lowest point of the structure, usually the rafter at the top of the wall.
Types of clear span framing
Clear span buildings can be constructed as single span or multi-span depending on the amount of square footage of floor space you need.
Single span rigid frame
A single span rigid frame building can be built from 30 feet to 12 feet wide and from 10 feet to 24 feet high at the eave. Anything smaller than 30 feet of larger than 120 feet cannot be constructed as economically with this frame type.
Occasionally, a single span frame can go to about 200 feet for special needs. You can use tapered or straight columns and don’t care about headroom at the exterior walls.
Single span is great for smaller buildings that need a substantial roof slope and large, clear heights in the middle.
Multi-span rigid frame
Multi-span rigid frames are also known as:
- Column and beam
- Post and beam
- Modular frame
Clear span buildings of this type are often used as distribution centers, factories, and very large warehouses.
Theoretically, multi-span rigid frames are unlimited as to size, but you need to add expansion joints at the spans every 300 feet or so for added stability. Rafters and columns can be tapered or straight, and additional interior columns may interrupt the space. The interior columns may be centrally located depending on the design or end-use application.
One difference from single span construction is that, because of the continuous framing, there may be uneven building movement as the ground settles underneath. It is more noticeable in the larger buildings. Also, the columns, once they are placed, are difficult to change in future updates to the building.
Advantages of steel frames
Along with its durability, steel confers a number of other advantages over wood, stone, or concrete construction.
- Steel can be formed into any shape and covered in any material, including more steel designed to look like stone, bricks, or any other facade.
- Steel is flexible and resists dynamic forces, making it ideal for areas with heavy seismic activity or high winds.
- Fabrication is performed off the jobsite; construction consists of bolting the frame together. A building can be erected much quicker and easier than using other materials.
- Steel frames are up to 90% lighter than a comparable frame of concrete.
Steel's dynamic flexibility and stability will come in handy as we see increased seismic activity throughout the country. Regions off the coasts of the Great Lakes, as well as the east and west coasts, also see a lot of high winds, as do the central Plains where tornadoes are a becoming more frequent.
In 2000, the steel building housing Fort Worth’s popular Reata restaurant and BankOne headquarters were hit by an F2 tornado. Most of the glass windows were blown out, but the frame resisted winds of 113 to 157 mph. Although the building was eventually demolished, the steel frame remained standing during and after the storm, saving the lives of those within.
A growing economy and population require more storage and more facilities with open space for activities. Sports arenas are a popular use for clear span construction as are the extremely broad warehouses and distribution centers of retailers like Amazon, Target, and Walmart.
Industrial farming and ranching also favor clear span buildings. Large numbers of animals can be housed out of the weather in a flexible floor arrangement of pens. Agricultural equipment from tractors to combines are more easily moved and stored inside a clear span building with a wide door. The same is true of municipal construction and road repair vehicles and machinery.
Clear span steel frame buildings have become one of the most popular building designs in the country, prized for their versatility, durability, and cost-effective construction.