Tee Joint — What It Is and Why It Matters
A tee joint (T-joint) is formed when one piece of metal is placed perpendicular (at 90°) to another, forming a T shape. It is one of the most common joint configurations in structural and fabrication welding, used for stiffeners, braces, column-to-beam connections, and general assembly.
Tee joints are almost always welded with fillet welds on one or both sides. Double-sided fillet welds provide balanced loading and resist moment forces better than single-sided fillets. The fillet weld size (leg length) is specified based on the thickness of the thinner member and the required load capacity.
When full-strength connections are required, tee joints may be beveled to allow complete-joint-penetration groove welds. This is common in structural steel moment connections and pressure vessel nozzle attachments where fillet welds alone cannot develop the required strength.
Frequently Asked Questions
Should I weld both sides of a tee joint?
For structural loads, welding both sides is strongly preferred — it provides balanced stress distribution and significantly higher strength. Single-sided fillets are acceptable for light-duty connections, brackets, and non-structural assemblies where full strength is not required.
What size fillet weld do I need?
Structural codes like AWS D1.1 specify minimum fillet weld sizes based on the thickness of the thicker member at the joint. As a rule of thumb, the fillet leg size should be approximately 3/4 of the thinner member's thickness for a full-strength connection. Always follow the engineer's specification when one is provided.