Vertical welding is one of the trickier positions to master because gravity is constantly working against you — molten metal wants to sag and drip downward before it solidifies. The good news is that with the right settings, travel direction, and technique, you can produce clean, consistent vertical welds without the frustrating drips and undercut that plague beginners.
Why Drips Form in Vertical Welding
Drips (also called sag or run-out) happen when the weld pool stays molten for too long or gets too large for gravity to support. The main culprits are:
- Too much heat — a large, fluid pool is hard to control vertically
- Too slow a travel speed — heat builds up and the pool grows
- Wrong electrode angle — not using the arc force to push the pool into the joint
- Incorrect weaving technique — pausing in the wrong spot lets metal pool and drip
Understanding these causes is the first step to fixing them.
Vertical-Up vs Vertical-Down: Which Should You Use?
There are two approaches to vertical welding, and choosing the right one matters.
Vertical-Down (Downhill)
- Travel from top to bottom
- Faster travel speed, less heat input
- Good for thin material (under about 4–5 mm) where burn-through is a risk
- Less penetration — not suitable for structural or load-bearing welds on thicker steel
- Easier for beginners to control drips because you're moving ahead of the pool
Vertical-Up (Uphill)
- Travel from bottom to top
- Better fusion and penetration into the base metal
- Required for most structural work and thicker sections
- More challenging — the pool wants to flow downward against your direction of travel
- The preferred method for most quality vertical welds
For structural steel work in NZ, vertical-up is generally required by welding procedures and standards such as AS/NZS 2980. Always check the applicable standard or welding procedure specification (WPS) for your job.
Reduce Your Heat Input
This is the single most effective fix. Compared to flat or horizontal welding, reduce your amperage or wire feed speed by roughly 10–15% when welding vertically. A smaller, stiffer weld pool is far easier to control.
| Process | Flat Setting (example) | Vertical Adjustment |
|---|---|---|
| MIG (GMAW) | 180 A / higher wire speed | Reduce wire speed 10–15% |
| Stick (SMAW) | Full rated amperage | Reduce 10–15% |
| Flux-core (FCAW) | Manufacturer's flat setting | Reduce per manufacturer's data |
Always refer to your consumable manufacturer's data sheet for specific vertical settings — these override general rules.
Electrode and Gun Angle
For vertical-up MIG or stick welding, hold the electrode or gun at roughly 5–15° upward from horizontal (a slight upward push angle). This directs the arc force into the joint and helps support the pool against gravity. Avoid pointing the gun downward — that pushes the pool away and encourages drips.
For stick welding, a drag angle of about 5–10° in the direction of travel works well.
Master the Weaving Technique
A controlled weave is essential for vertical-up welding on wider joints or when building up a fillet. The key rule: pause at the toes (edges), move quickly through the centre.
- Use a triangular or Z-weave pattern
- Pause briefly at each side of the weld to allow fusion and let the centre cool slightly
- Move briskly across the middle — this prevents heat from building up and the pool from sagging
- Keep your weave width to no more than 2.5–3 times the electrode diameter to maintain control
For thin material or a root pass, a stringer bead (no weave, straight up) is often better than a weave.
Use the Right Consumables
Not all electrodes and wires are equal for vertical work. Look for:
- Stick electrodes: E6013 is forgiving for beginners; E7016 and E7018 give better mechanical properties for structural work but require good technique and dry storage
- MIG wire: Standard ER70S-6 wire works well; use a short-circuit or pulsed transfer mode rather than spray transfer, which produces too much heat for vertical work
- Flux-core wire: Use gas-shielded flux-core (FCAW-G) designed for all-position welding — check the wire classification includes an 'AP' or 'all position' designation
Local welding suppliers and stores like Bunnings or Mitre 10 stock common consumables, though a specialist welding supplier will have a wider range and better technical advice.
Tack and Fit-Up Matter Too
Poor fit-up makes vertical welding much harder. Gaps that are too wide force you to fill with more passes and more heat. Ensure:
- Consistent root gap as per your joint design
- Good tack welds to hold alignment
- Clean, grease-free, rust-free base metal — contamination causes porosity and unstable arcs that contribute to drips
Practice on Scrap First
Before tackling your actual job, run a few practice beads on scrap steel of the same thickness. Dial in your settings, get comfortable with your weave rhythm, and check for drips, undercut, and fusion. Vertical welding is a skill that improves quickly with deliberate practice.
When to Call a Professional
Vertical welding on structural steel, pressure vessels, trailers, roll cages, or anything safety-critical should be carried out by a qualified welder with the appropriate certification under AS/NZS 2980 or the relevant standard. In NZ, structural welding on buildings may also intersect with Licensed Building Practitioners requirements and the NZ Building Code — check with your local council if you're unsure whether your project needs a building consent.
If your project involves gas pipework, always use a licensed gasfitter registered with the Plumbers Gasfitters & Drainlayers Board — welding on gas lines is restricted work.
For complex or structural welding jobs, you can find qualified local welders on tradedirectory.co.nz.
Safety Note
Always wear an auto-darkening welding helmet, leather gloves, and flame-resistant clothing. Vertical welding produces spatter that can fall onto your hands and body — ensure your PPE covers all exposed skin. Work in a well-ventilated area and be aware of fire risks from falling spatter. Refer to WorkSafe NZ for welding health and safety guidance.
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