IS 813 : 1986Scheme of Symbols for Arc Welding

IS 813:1986 is the scheme of symbols for arc welding — the standardised graphical symbols used on engineering/fabrication drawings to specify welded joints: weld type, size, length, location, finish and process. It is the communication standard that turns a welded-connection design (IS 800) into an unambiguous fabrication instruction.

It sits in the welding/steel stack:

• IS 816 — use of metal-arc welding (the welding *practice* the symbol instructs) · IS 800 — steel design (the connection being welded)
• IS 812 — coding of covered electrodes · IS 814 Part 1 — electrodes · IS 2062 — structural steel

A welded joint's strength depends on type, size, length, side and extent — all of which must be conveyed precisely from designer to fabricator/welder. IS 813 standardises that so it is read identically by everyone:

• The reference line, arrow, weld symbol, dimensions (fillet leg size, weld length/pitch for intermittent welds), side of joint (arrow-side vs other-side), field-weld and weld-all-round flags, and finish/process notes
• An ambiguous or missing symbol → the fabricator guesses the weld size/length, and an under-sized or intermittent-instead-of-continuous weld is a silent structural deficiency
• It is the bridge between the IS 800 design weld and the IS 816 executed weld — if the symbol is wrong, a correct design is built wrong

The engineering point: weld symbols are not draughting decoration — the fillet size and length in the symbol are the structural specification, and a misread or omitted symbol is one of the most common ways a correctly-designed connection becomes an under-strength one in the shop.

Scenario: detailing a fillet-welded structural connection designed to IS 800.

Step 1 — design the weld: IS 800 gives the required fillet size and effective length (and whether continuous or intermittent).

Step 2 — symbol it per IS 813: correct weld symbol with leg size, length/pitch (for intermittent), arrow-side vs other-side, weld-all-round/field-weld flags, and any finish/process note — unambiguous.

Step 3 — no ambiguity: every load-bearing weld carries an explicit size/length symbol; nothing left for the shop to assume.

Step 4 — fabricator reads it identically: the welder executes per IS 816 to the symboled size/length.

Step 5 — inspection checks against the symbol: weld size/length verified to the drawing, not to guesswork.

The symbol is the contract between design and fabrication — precise symbols give the designed weld; sloppy symbols give whatever the shop assumed.

1. Omitting weld size/length on the symbol. Forces the fabricator to guess — under-sized/intermittent welds become silent structural deficiencies.

2. Arrow-side / other-side errors. Putting the weld on the wrong side of the joint — a real, common detailing mistake.

3. Non-standard / improvised notations. Defeats the purpose; the value is everyone reading the *same* standardised symbol.

4. Intermittent vs continuous confusion. A pitch/length error turns a continuous design weld into an intermittent one (or vice-versa) — a capacity change.

5. Symbol not matched to the IS 800 design. The symbol must carry the *designed* size/length, not a default.

• IS 816 — use of metal-arc welding (the practice the symbol instructs) · IS 800 — steel design (the connection)
• IS 812 — coding of covered electrodes · IS 814 Part 1 — covered electrodes
• IS 2062 — structural steel · IS 3600 Part 1 — testing of welded joints

IS 813 is reaffirmed and easy to dismiss as draughting convention, but it is the contract between the welded-connection design and the steel that actually gets fabricated. The structural truth: the **fillet size and weld length in the symbol *are* the specification**, so an omitted, ambiguous or wrong-side weld symbol is a direct route from a correct IS 800 design to an under-strength built connection — the fabricator builds what the drawing says, not what the engineer intended. The discipline is unglamorous and absolute: every load-bearing weld carries an explicit, standard IS 813 symbol with size, length/pitch and side, matched to the design, and inspection checks the executed weld against that symbol (IS 816). Precise weld symbols are one of the cheapest, highest-leverage defenses against welded-connection failure.