If metal buildings could not be more than a single story tall then the skyline of every major city would look drastically different. Not to mention the bottom would fall out of the elevator business (sorry about the pun). In fact, it is because steel is so strong that we have these high-rises and skyscrapers today.
However, you may be asking about an existing building and the answer depends on the building and foundational design load, among other things. There are several benefits to multi-story steel buildings if you have planned properly. Let’s take a look at those benefits and some design principles for building a multi-story structure or building added floors onto an existing one.
Design principles for multi-story buildings
The design of a two-story building typically begins with the initial design of a building but if the original design is for a single-story structure, you can still build it as though more floors will be added in the future.
- As you determine the building requirements, plan as though you are building a multi-story building.
- When selecting grids and performing preliminary sizing, consider the possibility of steel building expansion at a future date and design a stronger foundation and framework.
- Ground conditions have a significant impact on the design of a multi-story building.
- Weight and cost of a structural frame per unit of floor area increases with height because the wind loading increases disproportionately.
Steel is particularly appropriate to multi-story construction because of the lateral stability it has when used as a continuous metal frame. The moment continuity between the beams and columns limit frame sway. Another option is to erect a braced frame to create resistance to lateral and torsional loads.
- Vertical bracing transfers horizontal forces to the ground and provides resistance against sway.
- Horizontal bracing at each story level braces the horizontal frame via the floor plates and transfers horizontal forces to the planes of vertical bracing.
- In theory, at least three vertical frames of bracing are required for resistance in both directions and resistance to torsion around the vertical axis. In real-world use, more than three frames are usually required to provide the appropriate amount of resistance.
Another advantage to steel is its high strength to weight ratio. Constructing a multi-story building using concrete requires extremely thick walls to ensure the building won’t collapse beneath its own weight. The need for thick walls decreases the amount of usable square footage inside the structure and takes up more space on the building site.
A weakness of building with concrete is its relative instability in seismically active areas. Where steel will bend and sway without breaking, masonry cracks, creating a hazard from falling concrete and increasing the chance of a total building collapse.
These design principles apply when determining whether you can add a second or third story to your steel building. Generally, if you have a steel-framed building you may only need to add basic steel bracing to add up to four additional stories.
How to expedite the design and build process
You can have a smooth start to increasing the height of your building if you do a little homework first.
- Check the local building codes to confirm the limitations to building height in your location.
- Examine the land formations, underground utility layout, and soil composition to ensure the site is appropriate for a multi-story building.
- Prefabricated metal buildings and frames reduce the time to assemble in comparison to traditional construction.
- Prefabricated frames also make it easier to build in a high-density area.
- Keep the design simple to shorten the construction time line.
The use of standardized parts from the beginning can make it easier to add on to a building later as well as expedite the building process in any phase. Using experienced steel building contractors can smooth out any remaining bumps in your road to adding stories to your metal building.
Advantages of a two-story steel building
The high-rise multi-story building only became feasible upon the invention of the lift, or elevator. Without a mechanical method of accessing anything above a few stories, it’s doubtful the high-rise would exist. Besides the fact that most of us are not willing or able to climb more than three or four flights of stairs, there are accessibility issues for buildings with no elevator.
As much as the elevator helped, the price of land has probably driven most buildings upward rather than outward. What are other advantages of two-story metal building?
- You can increase storage capacity within a structure.
- Additional stories increase the profitability of a structure by allowing specialized use from floor to floor.
- Multi-story buildings create an identity for many major cities.
- You have more design flexibility to meet restrictions or add architectural beauty.
However, without the strength and durability of steel, you wouldn’t have any of these advantages without purchasing more land and creating sprawling low-rise structures. Steel can withstand wind loads better than most concrete or stone buildings. Steel is also a more robust load-bearing material than concrete with the ability to carry more weight and therefore more stories.
Steel also has the advantage of reclamation and reuse. Recycled steel is every bit as strong as new steel and never loses that strength through repeated recycling. Using steel eliminates tons of waste from landfills and reduces the need to mine for iron.
If you already own a steel building and want to increase its profitability without buying additional land, adding a second or even third story onto your building isn’t a difficult choice. The original building has all the strength advantages of steel while the upper stories have the benefit of lightweight yet strong construction.
You can double or triple your commercial floor space or you can create upper story apartments with a store or other facility on the ground floor. If the ground floor is already apartments, you can increase your rentable space by building upwards. The steel frame allows the additional weight and the second floor is quickly constructed with standard beams and columns.
Can your metal building have two stories? Not a problem if you are building with steel.