An adjustable base jack—also called a screw jack or base jack—is one of those small components that quietly carries a lot of responsibility on a scaffolding job. It sits at the bottom of every standard or frame, transferring the load of the whole structure down to the ground and letting crews level the scaffold on uneven or sloping surfaces. Because it does so much heavy lifting, the material it is made from matters a great deal. Get the material right and the jack will hold up for years; get it wrong and you are looking at bent threads, cracked plates, and a scaffold that is no longer safe to work on.
So what materials are adjustable base jacks typically made from? The short answer is carbon steel—almost always Q235 or Q355—finished with a protective coating. But there is more to it than that, and the details are worth understanding whether you are buying your first batch or restocking for a large project.
The workhorse: carbon steel
The overwhelming majority of base jacks on the market are manufactured from carbon structural steel. In China, where most of the world’s scaffolding accessories are produced, the two grades you will see most often are Q235 and Q355.
Q235 is the standard choice for general-purpose base jacks. It is a mild carbon steel with a yield strength of 235 MPa, which is more than enough to distribute the load of a typical scaffold through the base plate into the ground. It is also easy to machine, weld, and thread, which keeps costs reasonable without sacrificing performance.
Q355 is the higher-strength option, offering a yield strength of 355 MPa. It comes into play when a project demands a heavier load capacity or when the engineer wants extra margin in the design. You will often see Q355 specified for heavy-duty work such as shoring, bridge construction, and industrial maintenance, where the scaffold carries more weight than a typical building-facade job.
These grades line up with well-known international designations—Q235 is broadly comparable to S235, and Q355 to S355—which makes it easier to match the material to the requirements of local standards.
Solid or hollow: two ways to build a jack
Beyond the grade of steel, base jacks come in two structural types, and each uses a different form of the same material.
A solid base jack is machined from a solid round steel bar. Because there is no hollow center, it offers the highest load-bearing capacity and is the preferred choice for heavy-duty scaffolding and shoring systems. Solid jacks are typically made from Q235 round bar with diameters ranging from about 30 mm to 34 mm.
A hollow base jack is formed from a steel pipe, which makes it lighter and easier to handle while still providing strong support for standard construction scaffolding. Hollow jacks are usually made from Q235 steel pipe with outer diameters of 38 mm or 48 mm, matching the tube sizes used in common scaffolding systems.
The choice between solid and hollow usually comes down to the load you need to carry and how much weight your crew wants to haul around the site. For most general construction work, a hollow jack is perfectly adequate; for heavy shoring and high-load applications, solid is the safer bet.
The base plate and the nut
The threaded screw is only part of the story. An adjustable base jack is made up of three main parts—the threaded bar, the base plate, and the nut—and each has its own material considerations.
The base plate is the flat square or round plate at the bottom that spreads the load across the ground. It is almost always made from carbon steel plate, commonly 150 × 150 mm with a thickness of 4 to 8 mm. Thicker plates are used where ground conditions are soft or where the load is particularly heavy, because a thicker plate distributes the pressure over a larger area and reduces the risk of the jack sinking into the soil.
The nut, which is what actually turns to adjust the height, is frequently made from cast steel or ductile iron. It needs to be tough enough to handle repeated adjustment without stripping the threads, and it is usually designed so that the thread engages smoothly with the rolled thread of the screw.
Surface treatment: what keeps the steel alive
Raw steel will rust. That is not a question of if, but when—especially on a construction site where equipment is exposed to rain, humidity, and the general abuse of daily use. That is why the surface treatment of a base jack is just as important as the material itself.
The most common finish is hot-dip galvanizing (HDG). The jack is dipped into molten zinc, which forms a thick, durable coating that protects the steel from corrosion for years. Hot-dip galvanized jacks are the standard choice for scaffolding that will be used outdoors or stored for long periods.
Electro-galvanizing is a thinner coating applied through an electrochemical process. It gives the jack a cleaner, brighter appearance and is often used where the jack will be handled indoors or where appearance matters more than maximum corrosion resistance.
Powder coating is another option, applied as a dry powder that is cured into a hard, colored finish. It offers good protection and a neat appearance, though it is less common for base jacks than for some other scaffolding components.
At Bythai Scaffolding, for example, base jacks are manufactured from Q235 and Q355 steel and are available with hot-dip galvanized, electro-galvanized, powder-coated, or pre-galvanized finishes, depending on the requirements of the project. All products are made in line with international EN and BS standards, and the factory is ISO9001 certified, so both the material quality and the coating process are controlled from start to finish.
Standards and quality control
Because the base jack carries the entire weight of the scaffold, quality control is not optional. Reputable manufacturers test the material grade, check the thread dimensions, and verify the coating thickness before the jacks leave the factory. Products that comply with EN and BS standards give you the confidence that the material, the dimensions, and the load capacity have all been checked against a recognized specification.
When you are sourcing base jacks, it is worth asking the supplier three questions: what steel grade is used, what surface treatment is applied, and which standards the product complies with. If the answers are clear, you are probably dealing with a manufacturer who knows what they are doing.
Choosing the right base jack for your project
To sum up, the material of an adjustable base jack comes down to three decisions:
- Steel grade: Q235 for general use, Q355 for heavy-duty and high-load work.
- Type: solid for maximum capacity, hollow for lighter handling.
- Finish: hot-dip galvanized for outdoor durability, electro-galvanized or powder-coated where appearance or indoor use matters.
If you are planning a project and need to match the right adjustable base jack to your scaffolding system, it helps to work with a supplier who can explain the options clearly and supply to your specification. Whether you need a solid base jack for heavy shoring or a hollow base jack for everyday construction, a reliable base jack from a manufacturer that controls both material and coating quality will keep your scaffold level, stable, and safe—and that is exactly what the component is there for.