EN 1993 Bolt Spacing & Edge Distance — Eurocode 3 Table 3.3

Complete reference for minimum and maximum bolt spacing and edge distances per EN 1993-1-8:2005 Table 3.3. Requirements for standard round holes, oversize holes, and slotted holes in European structural connections.

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Minimum Spacing and Edge Distances — Table 3.3

Parameter	Symbol	Minimum	Maximum
End distance (loaded toward end)	e₁	1.2 × d₀	4t + 40 mm
Edge distance (perpendicular)	e₂	1.2 × d₀	4t + 40 mm
Spacing parallel to load (between bolt rows)	p₁	2.2 × d₀	min(14t, 200 mm)
Spacing perpendicular to load (between bolt lines)	p₂	2.4 × d₀	min(14t, 200 mm)
Spacing in any direction	p₁, p₂	—	min(14t, 200 mm)

Where d₀ = hole diameter and t = the minimum plate thickness.

Minimum Values by Bolt Size

Bolt Size	d₀ (std)	e₁/e₂ min	p₁ min	p₂ min
M12	13.5	17 mm	30 mm	33 mm
M16	18.0	22 mm	40 mm	44 mm
M20	22.0	27 mm	49 mm	53 mm
M22	24.0	29 mm	53 mm	58 mm
M24	26.0	32 mm	58 mm	63 mm
M27	30.0	36 mm	66 mm	72 mm
M30	33.0	40 mm	73 mm	80 mm
M36	39.0	47 mm	86 mm	94 mm

Standard practice for M20: e₁ = e₂ = 30-40 mm, p₁ = 60-80 mm, p₂ = 60-80 mm.

Maximum Spacing Requirements

The maximum limits prevent plate buckling between bolts in compression zones:

Maximum p₁ = min(14 × t_comp, 200 mm) — parallel to load
Maximum p₂ = min(14 × t_comp, 200 mm) — perpendicular to load
Maximum e₁, e₂ = 4 × t + 40 mm

For a 10 mm thick compression plate:

Maximum p₁ = min(14 × 10, 200) = 140 mm
Maximum e₁ = 4 × 10 + 40 = 80 mm

For a 20 mm thick plate:

Maximum p₁ = min(14 × 20, 200) = 200 mm (capped)
Maximum e₁ = 4 × 20 + 40 = 120 mm

Special Hole Types — Clause 3.6.2

Oversize Holes

Bolt Size	Standard d₀	Oversize d₀	Spacing Adjustment
M12	13.5	15	p₁ + 1.5 mm
M16	18	20	p₁ + 2.0 mm
M20	22	24	p₁ + 2.0 mm
M24	26	28	p₁ + 2.0 mm
M30	33	36	p₁ + 3.0 mm

Oversize holes are used in slip-resistant connections to facilitate erection tolerances.

Short Slotted Holes

For short slotted holes (parallel to load direction), increase p₁ by the slot length minus the standard clearance.

Edge Distance and Spacing — Practical Guidance

Standard Connection Layouts

Connection Type	Recommended p₁	Recommended e₁	Recommended p₂	Recommended e₂
End plate (beam depth)	70 mm	40 mm	—	35 mm
Fin plate (simple)	60 mm	35 mm	60 mm	35 mm
Gusset plate (brace)	70 mm	35 mm	60 mm	35 mm
Column splice	80 mm	40 mm	80 mm	40 mm
Base plate	100-150 mm	50-75 mm	100-150 mm	50-75 mm

Corrosion and Fire Protection Allowance

For galvanized connections, add 3 mm to all edge distances to account for the galvanizing coating thickness. For fire-protected connections, ensure adequate clearance for fireproofing.

Frequently Asked Questions

What is the minimum edge distance for M20 bolts per EN 1993-1-8?

The minimum edge distance e₁ and e₂ for M20 bolts (d₀ = 22 mm) is 1.2 × 22 = 26.4 mm. In practice, use 30 mm minimum for standard details. For base plates with large anchor plates, 40-50 mm is more common.

Can I use bolt spacing less than the minimum per Table 3.3?

Per EN 1993-1-8 Clause 3.5(1), the minimum values in Table 3.3 are mandatory for design. Reduced spacing leads to reduced bearing resistance (lower α_b and k₁ factors) and increased risk of block shear failure. Spacing below 2.2 × d₀ is not permitted for structural connections.

Bolt Bearing & Tearout — Bearing per EN 1993-1-8 Clause 3.6
Bolt Group Capacity — Eccentric loads
Bolt Torque Chart — Torque-tension values
End Plate Connection — Moment connection
All European References

Educational reference only. Spacing requirements per EN 1993-1-8:2005 Table 3.3. Verify against project specification and National Annex requirements. Results are PRELIMINARY — NOT FOR CONSTRUCTION without independent verification.

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