Whether you’re installing equipment, building a steel structure, or setting up a sunroom at home, as long as it involves securing something firmly to the ground or a concrete foundation, one important component you’ll always need is the foundation bolt.
Foundation bolts may look simple, but in reality, there are many specifications and types. Choosing the wrong one can lead to instability at best and serious safety hazards at worst.Today, let’s go over foundation bolt specifications and dimensions in the simplest possible way and how to choose the right one for your project.
What Is a Foundation Bolt?
You can think of it as an anchor that connects your equipment to the ground.One end is embedded in the concrete foundation, and the other end passes through the base of the equipment. A nut is then tightened on top to fasten the equipment securely to the foundation, resisting various external forces such as wind, vibration, and overturning moments.
Key Specification
When reviewing a foundation bolt specification sheet, pay attention to below four core parameters:
1. Thread Specification (e.g., M20, M30)
This is the most important specification. It determines the size of the matching nut and the basic strength of the bolt itself.What does the “M” mean? “M” stands for metric thread, which is the most widely used international standard.
The number following it (e.g., M20) represents the nominal diameter of the bolt in millimeters.Choosing the correct diameter directly determines the tensile and shear strength of the bolt.
Small equipment (such as pumps or cabinets): M12, M16
Medium equipment (such as machine tools or steel columns): M20, M24
Heavy equipment (such as injection molding machines or wind turbine towers): M36, M48 or even larger
In summary,select based on the load requirements provided by the equipment manufacturer .It’s always safer to go slightly larger rather than smaller.
2. Length (L)
Is the length simply the total length? Not exactly , it’s important to distinguish between parts of it.
Embedment length (L₀):
It is the most important part. This is how deep the bolt is anchored into the concrete. Insufficient embedment is the most common cause of bolt pull out failures. Typically, the embedment should be 10–20 times the bolt diameter (for example, an M20 bolt should be embedded 200–400 mm). The exact value depends on design requirements.
Total length (L):
The total length = embedment length (L₀) + exposed length. The exposed part should be long enough to pass through the equipment base, washers, and leave sufficient threads for the nut to tighten securely.
| Thread Spec | Recommended Embedment (mm) | Typical Total Length (mm) | Common Applications |
|---|---|---|---|
| M12 | 120–240 | 300–400 | Light duty pumps, cabinets |
| M16 | 160–320 | 400–500 | Small steel columns |
| M20 | 200–400 | 500–600 | Machine bases, medium equipment |
| M24 | 240–480 | 600–700 | Structural columns |
| M30 | 300–600 | 700–900 | Heavy equipment |
| M36 | 360–720 | 900–1100 | Wind turbine towers |
(This table is for general reference only. Always follow the structural engineer’s design and specifications for your project.)
3.Material and Strength Grade
These determine how much “muscle” the bolt has.
Materials:
The common materials we usually use are Q235 steel (equivalent to A36), 45# steel, 40Cr alloy steel, etc. Q235 is the most economical and widely used,40Cr has higher strength.
Strength grades:
4.8, 8.8, etc.The number before the decimal (e.g., “8”) represents 1/100 of the tensile strength.For example, 8.8 grade bolts have a tensile strength of 800 MPa.The higher the grade, the stronger the bolt. For heavy equipment, we recommend to use 8.8 grade.
4.Type (Shape)
Foundation bolts has several shapes depending on the installation method and load conditions. Choosing the correct type is just as important as choosing the right size.
Common types include:
| Type | Appearance Features | Typical Applications | Advantages |
|---|---|---|---|
| “Eye” Shape Foundation Bolt | One end forms a closed loop (eye) while the other end is threaded | Used in light to medium installations, such as small machinery, pipelines, or fencing structures | Easy to install and connect; provides reliable anchoring for tension and pulling forces |
| “Double Ends” Thread Rod Foundation Bolt | Both ends are threaded, allowing nuts on each side | Commonly used for machinery bases, steel structures, and equipment that require precise height adjustment | Adjustable and easy to dismantle or replace; offers strong tensile strength and flexibility |
| “U” Shape Foundation Bolt | Bent into a “U” shape with threaded ends on both arms | Used for securing round objects like poles, pipes, or cylindrical tanks to concrete surfaces | Provides firm clamping for round components; distributes load evenly on both sides |
| “Stiffener Type” Foundation Bolt | Features a welded stiffening plate or rib near the bent or embedded end | Heav duty machinery, industrial columns, and structural supports subject to large horizontal or dynamic loads | Excellent resistance to bending and vibration; ensures high structural stability |
| “J” Shape Foundation Bolt | The lower end is bent into a “J” hook, upper end threaded | Most commonly used type for general equipment foundations, columns, and steel structures | Strong anchoring performance; effective in resisting uplift and pull out forces |
| “L” Shape Foundation Bolt |
Lower end bent into an “L” shape at 90 degrees; upper end threaded | Most common type for general foundation anchoring of machines and structural columns | Simple structure, good anchoring performance, and reliable resistance to tensile forces |
If you’re facing difficulties choosing the right foundation bolts, or need special sizes or materials, we’re ready to provide full technical support.FastenMetal specialize in manufacturing high strength foundation bolts and offer custom, non-standard solutions to secure your projects with quality and precision.
