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Vriksai Timber Intelligence

Screw Spacing Calculator

Calculate withdrawal and lateral capacity for wood screws, lag bolts and nails. NDS 2018, Eurocode 5, IS 883:2016, AS 1720 with group factor.

NDS 2018 USAIS 883 IndiaEurocode 5 EUAS 1720 AUPDF Report
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Screw Spacing — Calculator

Calculate withdrawal and lateral capacity for wood screws, lag bolts and nails. NDS 2018, Eurocode 5, IS 883:2016, AS 1720 with group factor.

Standard, Fastener & Load
Dimensions
mm
mm
pcs
✓
Minimum Spacing & Distances
—
mm
Spacing in Row (a1)
—
mm
Row Spacing (a2)
—
mm
End Distance, loaded (a3,t)
—
mm
Edge Distance, loaded (a4,t)
Formula Trace
📏 Screw Spacing Calculator
Gives the minimum spacing, end distance and edge distance for screws, nails and bolts in timber connections — the six code distances that decide whether a joint holds or the wood splits. Includes a layout check that fits your fastener count into the member.
Where Used?
Structural TimberLedger BoardsDecking FramesTrusses & GussetsFurniture JointsPergolas
Formulas
EC5 Table 8.2 (nails) — e.g. a1 = (5+5|cosα|)d, a3,t = (10+5cosα)dEC5 Table 8.4 (bolts) — a1 = (4+|cosα|)d, a3,t = max(7d, 80 mm)EC5 8.7.2 — screws d ≤ 6 mm follow nail rules, d > 6 mm follow bolt rulesIS 883 bolted — row spacing 4d, rows 4.5d, loaded end 7d
About the Screw Spacing Calculator
Most split boards and failed joints trace back to the same mistake — fasteners placed too close to an edge, an end, or each other. Design codes solved this long ago with minimum distance rules, but the rules change with fastener type, diameter, predrilling and load direction, which is why people end up guessing. This calculator applies the Eurocode 5 tables and the commonly specified IS 883 values directly, then runs a practical layout check: how many rows fit your member width, and how long the joint must be for the fasteners you need. It works as a timber fastener spacing reference for structural screw and bolt connections, and answers the timber connection design questions that generic span tables never cover.
Where Is This Used?
Furniture AssemblyHardware FixingDeck BuildingJoinery ConnectionsIndian Hardwoods
FAQ
What is the quick rule of thumb for screw spacing in wood?
For everyday joinery: keep screws about 10 diameters apart along the grain, 5 diameters from an end and 3 from an edge, and pre-drill hardwoods. Those track the code values closely — this tool gives the exact figures per standard.
Why is the end distance so much bigger when the joint is in tension?
A loaded end is where the wood can shear out in a block ahead of the fastener. EC5 asks up to (10+5cosα)d at a loaded end for non-predrilled nails versus 10d unloaded, and bolts need max(7d, 80 mm). Compression ends can be shorter because the load pushes wood together instead of tearing it away.
Does pre-drilling really let me place fasteners closer?
Yes, substantially. A pilot hole removes the wedge action that splits the wood, so EC5 drops nail spacing from (5+5cosα)d to (4+|cosα|)d and end distance from (10+5cosα)d to (7+5cosα)d. In dense hardwoods pre-drilling is effectively mandatory anyway.
Should I use the EC5 or IS 883 setting in India?
For most Indian site and workshop work, the IS 883 values are what inspectors and older drawings reference. EC5 is more detailed — it distinguishes nail, screw and bolt behaviour and predrilling — so many engineers design to EC5 and check IS. When the two disagree, using the larger distance is never wrong.
Can I stagger fasteners to squeeze more into a narrow member?
Staggering rows lets adjacent fasteners sit closer along the length while keeping true point-to-point distances legal, and it spreads the split risk across growth rings. The row spacing (a2) and edge distances still apply — staggering helps most when member width limits you to one straight row.
ResourcesView the formulasFormula Library
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Wood species data
Working with a specific timber? See full density, hardness and movement data for Ipe Lapacho, Iroko and Jarrah — or browse all 60+ wood species. Species strength values for the members themselves are in the strength properties reference.