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Fastener Spacing Calculator for Nails and Screws

Minimum nail and screw spacing, end and edge distances in timber from Eurocode 5 Table 8.2 or NDS guidance, with a dimensioned plan and a member fit check.

Fastener spacing calculator

Minimum spacing, end distance and edge distance for nails and small screws in timber, from Eurocode 5 Table 8.2 or the NDS Commentary recommendations. Placement geometry only: no load capacity is calculated.

MethodEurocode 5 uses density and the force angle. The NDS Commentary table uses multiples of D only.UnitsDiameter and member sizes.FastenerSize presetDiameters from the site's nail and screw size tables.Diameter d (mm)Shank diameter of the nail.Predrilled holesPredrilling is applied automatically where EN 1995-1-1 requires it.Side memberSteel: a nailed or screwed steel plate on the timber.TimberEN 338 characteristic density ρk (5th percentile).Angle between force and grain α (°)0° = force along the grain, 90° = across it. For a force pointing away from the end, keep α between 0° and 90° and choose “Away from the end” below instead of an angle above 90°.Species sensitive to splittingEN 1995-1-1 names fir, Douglas fir and spruce. Changes only the thickness rule.Force relative to the nearest endToward the end = loaded end (tension). Away = unloaded end (compression).Check a memberDoes the fastener group fit the member?Member width across the grain (mm)Member thickness (mm)In the direction the fastener is driven.Fasteners per line, along the grainLines across the width

After you calculate, print and download options will appear.

Result

Choose a method, fastener and diameter, then calculate the minimum spacing and edge and end distances.

How it works

Nails and screws split timber when they sit too close to each other, to an end or to an edge. Both Eurocode 5 and the American NDS deal with this through placement rules expressed as multiples of the fastener diameter d. This calculator returns those minimum distances, draws them on a plan of the fastener group and checks whether the group fits a member of the width and thickness you enter.

In Eurocode 5 mode the values come from EN 1995-1-1 Table 8.2. They depend on the diameter, whether the holes are predrilled, the characteristic density of the timber and the angle α between the force and the grain. Screws of 6 mm or less use the same table (clause 8.7.1(5)). Predrilling is switched on automatically when the standard requires it: density above 500 kg/m³, nails over 6 mm, any screw in hardwood, or a member thinner than expression (8.18).

The NDS gives no placement table for nails and wood screws. It only requires spacing that prevents splitting (12.1.5.7 and 12.1.6.5). Its Commentary offers recommended minimums for diameters below 1/4 in, and NDS mode returns those, labelled as recommendations.

Formula

EC5 Table 8.2, ρk ≤ 420 kg/m³, not predrilled: a1 = (5 + 5|cos α|)d for d < 5 mm, (5 + 7|cos α|)d for d ≥ 5 mm; a2 = 5d; a3,t = (10 + 5 cos α)d; a3,c = 10d; a4,t = (5 + 2 sin α)d for d < 5 mm, (5 + 5 sin α)d for d ≥ 5 mm; a4,c = 5d.
EC5, 420 < ρk ≤ 500 kg/m³, not predrilled: a1 = (7 + 8|cos α|)d; a2 = 7d; a3,t = (15 + 5 cos α)d; a3,c = 15d; a4,t = (7 + 2 sin α)d or (7 + 5 sin α)d; a4,c = 7d.
EC5, predrilled: a1 = (4 + |cos α|)d; a2 = (3 + |sin α|)d; a3,t = (7 + 5 cos α)d; a3,c = 7d; a4,t = (3 + 2 sin α)d or (3 + 4 sin α)d; a4,c = 3d.
EC5 8.3.1.4, steel side plate: a1 and a2 × 0.7. Thickness below which to predrill, (8.18): t = max(7d, (13d − 30)ρk/400); species sensitive to splitting, (8.19): t = max(14d, (13d − 30)ρk/200).
NDS Commentary, wood side member, not prebored / prebored: edge 2.5D / 2.5D; end (tension) 15D / 10D; end (compression) 10D / 5D; in a row parallel to grain 15D / 10D; perpendicular 10D / 5D; between rows in-line 5D / 3D; staggered 2.5D.
Member fit: width needed = a4,t + (lines − 1) × a2 + a4,c; distance from the end to the farthest fastener = end distance + (fasteners per line − 1) × a1.

Worked example

Two lines of three 3.1 mm nails fix a 45 × 95 mm C24 member (ρk = 350 kg/m³, not predrilled), with the force along the grain (α = 0°) pulling toward the member end. Table 8.2 gives a1 = (5 + 5 × 1) × 3.1 = 31 mm, a2 = 5 × 3.1 = 15.5 mm and a3,t = (10 + 5) × 3.1 = 46.5 mm.

Both edges need 5d = 15.5 mm, so the two lines take 15.5 + 15.5 + 15.5 = 46.5 mm of the 95 mm width. Along the grain the farthest nail sits 46.5 + 2 × 31 = 108.5 mm from the end.

Expression (8.18) gives max(7 × 3.1, (13 × 3.1 − 30) × 350 / 400) = 21.7 mm, so the 45 mm member does not need predrilling. Turn the force to 90° and the loaded-edge distance grows to (5 + 2) × 3.1 = 21.7 mm while a1 drops to 15.5 mm.

Common mistakes

Measuring edge distance from the face of the board instead of from the edge to the centre of the fastener.
Using the unloaded end distance when the force pulls the fastener toward the end.
Using mean density where Eurocode 5 asks for characteristic density ρk.
Treating a structural screw like a plain wood screw; self-tapping screws have spacing in their own European Technical Assessment.
Reading minimum spacing as proof that the connection is strong enough.

Scope and limits

Placement geometry only: minimum spacing, end distance and edge distance. No lateral or withdrawal capacity, number of fasteners, effective number nef, block shear or steel plate check.
Eurocode 5 values are the recommended values in EN 1995-1-1; a National Annex can change them. Timber-to-timber and steel-to-timber only; panel-to-timber rules (8.3.1.3) are not modelled.
Eurocode 5 mode covers nails up to 8 mm (8.3.1.1(6) sends larger nails to the bolt rules) and laterally loaded screws up to 6 mm (8.7.1(4)–(5)). Axially loaded screws (Table 8.6) and larger screws (bolt rules, 8.5.1) are not covered.
NDS mode covers diameters below 1/4 in using the Commentary's recommended minimums, which are not mandatory. NDS Tables 12.5.1A–D for larger fasteners are not covered.
Species presets estimate ρk as Wood Handbook mean density ÷ 1.2, the mean-to-characteristic ratio of the EN 338 C classes. North American species are not EN 338 graded, so the estimate is approximate; for Eurocode 5 work, use the strength class or the supplier's declared ρk.

Read the full guide with worked examples

Common questions

How far from the edge should a screw be in timber?

Under Eurocode 5, a screw of 6 mm or less follows the nail rules: 5d from an unloaded edge in timber up to 420 kg/m³ without predrilling, or 3d with predrilled holes. The NDS Commentary recommends 2.5D. The loaded edge can need more, depending on the angle of the force.

Why is the loaded end distance larger than the unloaded one?

When the force pushes a fastener toward the end of a member, the wood in front of it is what resists, and it can shear out or split. Eurocode 5 adds 5d cos α to the end distance for that case.

Does predrilling really allow closer spacing?

Yes. A predrilled hole removes the wedging that splits the wood, so Table 8.2 allows a1 of (4 + |cos α|)d instead of 10d to 15d along the grain without predrilling. The NDS Commentary similarly reduces most of its recommendations.

What spacing does the NDS require for nails and wood screws?

The NDS 2018 specification itself only says the spacing must prevent splitting. Its Commentary tables give recommended minimums, such as 15D along the grain in a row without prebored holes, for diameters below 1/4 in.

Does this apply to self-tapping structural screws?

Use the screw's European Technical Assessment or evaluation report instead. Those products are tested for their own spacing, which often differs from Table 8.2.

Does this tell me how many fasteners I need?

No. It only places fasteners so the wood is unlikely to split. How many you need depends on the load, which an engineer works out from the design rules for load capacity.

Sources

EN 1995-1-1:2004+A1:2008 Eurocode 5: Design of timber structures, Part 1-1European Committee for Standardization (CEN); index page from the EU Joint Research CentreThe standard is sold by national standards bodies. Clauses used here, read from the BS EN 1995-1-1:2004+A1:2008 text: 8.3.1.1(2) predrilling above 500 kg/m³ or for nails over 6 mm; Table 8.2 minimum spacings and end and edge distances; expressions (8.18) and (8.19) for the thickness below which timber should be predrilled; 8.3.1.4 steel-to-timber spacing factor 0.7; 8.7.1(5) smooth shank screws of 6 mm or less follow the nail rules of 8.3.1; 10.4.5(1) predrilling for all screws in hardwood.
Design of timber structures, Volume 2: Rules and formulas according to Eurocode 5 (edition 3:2022)Swedish WoodOpen reproduction used to cross-check Table 8.2 (its Table 10.2), the 0.7 steel-to-timber factor and the rule that the nominal diameter d, not the effective diameter, sets screw spacing (section 10.6.1). Its Table 3.3 gives EN 338:2016 characteristic and mean densities for C14 to C40; mean ÷ characteristic is 1.19 to 1.21 across those classes, the basis of the ÷ 1.2 estimate used for ungraded species.
National Design Specification for Wood Construction, 2018 Edition, Chapter 12: Dowel-Type FastenersAmerican Wood Council12.1.5.7 (wood screws) and 12.1.6.5 (nails and spikes): edge distances, end distances and spacings shall be sufficient to prevent splitting of the wood. No table is given for these fasteners. 12.1.5.3 requires lead holes for laterally loaded wood screws; 12.1.6.2 limits bored holes for nails to 90% of the diameter where G > 0.6 and 75% where G ≤ 0.6.
NDS 2018 Commentary, C12.1.5.7 and C12.1.6.5, Tables C12.1.5.7 and C12.1.6.6 (pp. 254–255)American Wood CouncilFor diameters less than 1/4 in, specific requirements are not provided, but the commentary tables of recommended minimum spacing may be used to establish placement. Both tables give the same multiples of D for wood screws and nails, with columns for wood and steel side members, prebored or not.