What is the difference between weld-up construction and a pre-engineered steel building?
If you look at a completed structure, you might not be able to tell, at least not right away. But if you take away everything but the frame, you can easily see the differences. Below is a comparison of the two construction methods for steel buildings. Each has its pros and cons.
What is weld-up?
A weld-up (field-welded) steel frame is just what is sounds like; the frame members are permanently fastened together with molten metal, or welding material.
Weld-up buildings typically require fewer parts, and less retooling than other kinds of construction and a welded joint can be stronger than a bolted one. You can even get steel members with weld-plates built-in, speeding up placement and making it easier for non-welders to construct.
A weld-up building needs a concrete pad designed to bear the weight of the standard hot rolled members, creating added strength and stability at the base. It’s a good choice for storage units, a workshop, or other enclosed steel structure.
Constructing a weld-up steel building
Weld-up steel buildings are not truly engineered; they are fabricated on the jobsite from locally sourced steel pipe or conventional metal framing of mill-produced hot rolled steel beams and columns.
Depending on the availability of materials and transportation, you may be able to receive the framing materials fairly quickly. If special architectural details are required, they will have to be developed for each project.
Everything is measured, cut, and welded including the trusses. Upfront costs are lower than a pre-engineered building, but extra materials are required because the members are not pre-measured, they are simply standardized lengths that must be cut on-site.
In some areas, permitting for a weld-up is difficult to obtain; depending on the region, weld-up buildings are disallowed by the building code. Once you have the permit, you will need specialized labor skilled in cutting and welding steel members. The weight of the building is unknown; the foundation will have to account for that, potentially being designed as a larger, heavier concrete pad than one required for a pre-engineered building where the exact weight is a known factor.
Every weld must be inspected, tested, and approved individually before the building can be completed.
If a weld-up building frame is damaged, the only way to repair it is to cut out the welded section and replace it. A welded joint cannot be disassembled to make repairs or to move, renovate, or change the shape of the building. Additionally, rigid welds and heavier frames don’t perform well during seismic movement.
However, it is a very strong building since the frame members are permanently connected using full welds. As for cost, a weld-up building is more economical than many bolt-up structures.
What are pre-engineered steel buildings?
You may hear it called a pre-engineered, prefabricated, or pre-manufactured metal building; the terms all mean the same thing. Every piece of the steel building, from members and fasteners to panels, has been fabricated in a manufacturing environment.
Quality control is highly developed in manufacturing environments; everything is fabricated to strict specifications. Materials are from a single source, improving accountability and safety. Pre-engineered steel buildings are particularly favored in seismically active areas.
Steel panels and members plus fasteners are relatively flexible, less likely to break if bent, even at the connections.
Everything is cut, factory-welded, punched, and marked: the columns, rafters, girts, and purlins. High strength bolts are included. There is no waste material to dispose of at the site.
Erecting a pre-engineered steel building
Pre-engineered buildings are professionally designed and fabricated at the vendor. Everything is cut and punched to fit together like a model. Once all the pieces are formed, everything is put together in a kit and delivered to the jobsite in six to eight weeks, ready to be put together.
As part of the design process, the building is engineered to meet the appropriate building codes and load requirements. You can obtain engineer stamped plans that can make permitting easier.
Most pre-engineered steel buildings require only a simple foundation to support the lighter weight. Frame members are tapered to reduce weight and material usage. Flanges are included to make mating and fastening easier. Most of the web is made of differing thicknesses and depth to more closely match internal stress points.
Overall, the construction of the metal frame can be achieved with less-skilled labor, and the weight of the building is about 30% less than a comparable conventional steel building.
Repairing, renovating, or moving a pre-engineered building is performed with relative ease by taking apart the joints and replacing any damaged pieces or reassembling the building elsewhere.
Which to choose?
Deciding between a weld-up steel building versus a pre-engineered steel building comes down to a couple of factors.
Weld-up steel buildings tend to have a lower up-front cost. There is no waiting for design or manufacturing, you obtain the steel members locally in standard lengths and cut them to the needed size.
Members are welded together, forming a strong and rigid structure that is durable and long-lasting. If you are on a budget and are confident the building will need no changes in the future, a weld-up steel building is a bargain.
On the other hand, if you anticipate the need to make changes to the building or inexpensively to add architectural detail, a pre-engineered steel building may be the best choice.
It will cost more up front, but the ease of maintenance, repairs, and additions to the building make up for it. Pre-engineered buildings are quickly and easily erected with little special skill required to put up the primary and secondary framing members.
The high-quality assurance and testing program at the manufacturer virtually guarantees everything fits together properly with no waste materials left over. Pre-engineered buildings are preferred in seismically active areas where you need something a little more flexible than a welded joint.
Do you have any thoughts about either weld-up or pre-engineered buildings you would like to share?