Quick answer: the American Welding Society (AWS) recognises five basic welding joints: butt, tee (T), corner, lap and edge. The joint is how the parts meet, and the weld is what you put in it, usually a fillet weld (in a corner) or a groove weld (in a gap between edges).
The 5 types of welding joints
1. Butt joint
Two pieces lie in the same plane, edge to edge. It’s the most common joint for plate and pipe.
- Welded with a groove weld. Thin metal can use a square edge; thicker metal is bevelled (a V, bevel, J or U groove) so the weld can penetrate fully.
- Used for pipelines, plate structures, tanks and vessels.
2. Tee (T) joint
One piece meets the middle of another at about 90°, forming a T.
- Usually welded with fillet welds on one or both sides. Thick sections may get a bevel for full penetration.
- Used for frames, brackets, structural steel and trailer cross-members.
3. Corner joint
Two pieces meet at their edges, at about 90°, forming an L.
- Can be an open corner (edges flush, welded on the outside, often with little or no filler) or a closed corner (one piece overlapping, fillet welded on the inside).
- Used for boxes, frames, enclosures and sheet-metal fabrication.
4. Lap joint
Two pieces overlap in parallel planes.
- Welded with fillet welds along one or both edges. Also used for plug, slot and spot welds.
- Easy to fit up and good for joining different thicknesses. It’s common in sheet metal and auto body work.
5. Edge joint
Two pieces lie side by side, and the weld runs along their edges.
- Used mainly for thin sheet and flanged parts, not for high-stress joints.
- Often welded without filler (especially with TIG).
Fillet welds vs groove welds
| Fillet weld | Groove weld | |
|---|---|---|
| Shape | Roughly triangular, in a corner | Fills a gap between edges |
| Joints | Tee, lap, corner | Butt, corner, some tee |
| Edge preparation | Usually none | Often bevelled |
| Sized by | Leg length (e.g. 1/4” fillet) | Depth and penetration |
| Typical use | Frames, brackets, general fabrication | Pipe, plate and full-strength joints |
Other weld types you’ll hear about: plug and slot welds (through a hole in one piece), spot and seam welds (resistance welding, common in car bodies), surfacing welds (building up worn parts) and back welds (on the reverse side of a groove weld).
Edge preparation for groove welds
| Groove | When it’s used |
|---|---|
| Square | Thin material, about 1/8”–3/16” (3–5 mm) or less, depending on the process |
| Single V or bevel | Medium plate, welded from one side |
| Double V or bevel | Thick plate, welded from both sides to reduce distortion |
| J or U | Thick sections; needs less filler than a V, but is harder to machine |
A small root gap and a land (a flat edge at the root of the bevel) help the root pass penetrate without burning through.
Welding positions
Positions describe where the joint sits relative to you. The number is the position, F means fillet weld and G means groove weld.
| Position | Plate (fillet / groove) | Description |
|---|---|---|
| Flat | 1F / 1G | Welding from above, the easiest position |
| Horizontal | 2F / 2G | Joint runs horizontally on a vertical surface |
| Vertical | 3F / 3G | Weld runs up (or down) a vertical joint |
| Overhead | 4F / 4G | Welding from below, the hardest plate position |
Pipe positions add 5G (pipe horizontal and fixed, welded all the way around) and 6G (pipe fixed at 45°, covering every position). The 6G test is the classic all-position pipe welding certification. Learn more in our guide to GTAW pipe welding.
Choosing a joint
- Strength needed: full-penetration groove welds carry the most load. Fillet welds are fine for most frames and brackets.
- Material thickness: thicker material needs bevels and multiple passes.
- Access: can you reach both sides? If not, choose a joint that can be welded from one side.
- Distortion: balanced welds (both sides of a tee, or a double V) reduce warping.
- Cost and time: lap and fillet joints are quickest to prepare, while bevelled butt joints take more preparation.
FAQ
What are the 5 basic types of welding joints?
Butt, tee (T), corner, lap and edge.
What is the strongest welding joint?
A properly made full-penetration butt joint (groove weld) is typically the strongest, because the weld can match the strength of the base metal.
What is a fillet weld?
A roughly triangular weld that joins two surfaces at an angle, usually in a tee, lap or corner joint. It’s the most common weld in general fabrication.
What does 6G mean in welding?
A pipe welding position where the pipe is fixed at 45°, so the welder has to weld in flat, vertical and overhead positions in one joint. It’s a common certification test.
How this guide was written: joint and position names follow American Welding Society (AWS) terminology. Related: types of welding processes and our stick welders for beginners. See how I test and review.