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# Design a Timber Nail Connection to AS 1720.1:2010
> Check the capacity of nailed timber connections to AS 1720.1:2010.
Design rectangular nail groups to AS 1720.1:2010. Checks direct shear capacity (Cl 4.2.3.2), in-plane moment capacity (Cl 4.2.3.3), and withdrawal capacity (Cl 4.2.3.4) for timber-to-timber and timber-to-steel connections.
## Method & scope
| Property | Detail |
| ---------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| Design standards | AS 1720.1:2010 |
| Regions | Australia & New Zealand |
| What it checks | Joint type and nail position, Characteristic fastener capacity, Load combinations and load duration factor k\_1, Rectangular pattern capacity, Type 1 (shear) joints, Type 2 (tension/withdrawal) joints, Joint category factor |
#### Calculation method
##### Joint type and nail position
The first input is joint type and nail position, which sets two key modification factors from AS 1720.1:2010 Figures 4.2 and 4.4:
* **Type 1 (shear) joints**, nails are loaded laterally. Side grain positions use k\_13 = 1.0; end grain positions use k\_13 = 0.6. Single shear gives k\_14 = 1.0; double shear gives k\_14 = 2.0.
* **Type 2 (tension) joints**, nails are loaded axially in withdrawal. Side grain uses k\_13 = 1.0; end grain uses k\_13 = 0.6.
##### Characteristic fastener capacity
For the selected nail diameter and the joint group of the receiving timber member, the calculator looks up the characteristic lateral capacity Q\_k (Type 1) or the characteristic withdrawal capacity Q\_wk per unit penetration (Type 2) from AS 1720.1:2010 Section 4.2 tables. Joint group is determined by the timber species and seasoning condition, a seasoned hardwood such as F17 carries a higher joint group rating than a softwood such as MGP10.
##### Load combinations and load duration factor k\_1
Applied loads (dead, live, wind, earthquake, etc.) are entered per load type. The calculator assembles AS/NZS 1170.0 strength load combinations and identifies the governing combination. The load duration factor k\_1 is applied to the demand side, it reflects the characteristic strength reduction for sustained loads and takes values of 0.57 for permanent actions, 0.69 for floor live, 0.77 for roof live, 0.94 for wind, and 1.14 for earthquake.
##### Rectangular pattern capacity, Type 1 (shear) joints
For a rectangular pattern of n\_x columns and n\_y rows with spacings s\_x and s\_y, the calculator derives:
**Direct shear capacity (Cl 4.2.3.2):**
V\_d,j = joint\_category\_factor × k\_13 × k\_14 × n × Q\_k
where n = n\_x × n\_y is the total nail count.
**In-plane moment capacity (Cl 4.2.3.3):**
The polar second moment of area of the nail pattern about its centroid is computed from the spacings. The moment capacity M\_d,j corresponds to the most critically loaded nail at maximum distance from the centroid, scaled by the same characteristic fastener capacity.
The combined utilization for simultaneous shear and moment loading:
(V\* / V\_d,j)² + (M\* / M\_d,j)² ≤ 1.0
##### Type 2 (tension/withdrawal) joints
The withdrawal capacity per nail is derived from the characteristic withdrawal capacity Q\_wk and the penetration depth t\_p into the receiving member. For the full pattern:
N\_d,j = joint\_category\_factor × k\_13 × n × Q\_wk × t\_p
The demand N\* is compared against N\_d,j (Cl 4.2.3.4) and the utilization ratio is reported.
##### Joint category factor
The joint category (Category 1 to 4 per AS 1720.1 Table 2.5) applies a capacity reduction factor reflecting structural risk and inspection level. Category 1 (house construction) uses base characteristic values; higher categories apply increasing reduction factors to the calculated capacity.
##### Outputs and pattern diagram
The calculator displays a visual cross-section diagram of the nail pattern, updating in real time as geometry inputs change. Output utilization ratios are color-coded: green for pass, red for fail. Each check, Shear, Moment, and Tension, shows the demand, capacity, and utilization ratio with the corresponding AS 1720.1 clause number, making outputs directly traceable to the standard for documentation and peer review.
## How to use it
Open it from **Run calc** in the About this calculator panel above.
Work through the input sections from top to bottom. Click any input label to see its reference explanation, clause, conditions and assumptions. See [Checks, References, Conditions and Assumptions](/docs/running-calculations/checking-results/checks-references-conditions-assumptions).
Check the utilization of each governing check in the summary, then export a PDF report. See [Views and Export](/docs/running-calculations/exporting-reports/views-and-export).
## Common questions
AS 1720.1:2010 (Timber Structures). The calculator applies Section 4.2 of that standard to determine the design capacity of nailed connections, using characteristic values for lateral (shear) and withdrawal capacity, combined with joint category factors and load duration factor k\_1.
Joint type and nail position (side grain or end grain; single or double shear for Type 1, or withdrawal for Type 2), nail size and type, timber species and joint group, rectangular pattern geometry (n\_x nails in X, n\_y in Y, spacings s\_x and s\_y), penetration depth t\_p, joint category, and applied shear/moment or tension loads with load types for AS/NZS 1170 load combinations.
For Type 1 (shear) joints, the calculator outputs direct shear demand V\* and capacity V\_d,j (AS 1720.1 Cl 4.2.3.2), and in-plane moment demand M\* and capacity M\_d,j (Cl 4.2.3.3), each with a utilization ratio. For Type 2 (tension/withdrawal) joints it outputs withdrawal demand N\* and capacity N\_d,j (Cl 4.2.3.4). The governing utilization ratio is flagged in the calculation header.
The calculator supports Type 1 (lateral shear) and Type 2 (withdrawal) joints as separate modes per AS 1720.1 Figures 4.2 and 4.4. Select the joint type that matches your connection, Type 1 for nails loaded laterally in side grain or end grain, Type 2 for nails loaded axially in withdrawal. Combined shear-withdrawal is not evaluated within a single check.
The calculator checks pattern capacity under the specified load case. Minimum spacing, end distance, and edge distance requirements per AS 1720.1 Table 4.5 must be verified separately, the calculation notes this assumption explicitly. The pattern geometry diagram updates in real time as you adjust n\_x, n\_y, s\_x, and s\_y.
## Next steps
Complete list of Calcs.com design calculators available for Australian and New Zealand projects (AS 3600, AS 4100, AS 1720, AS/NZS 1170, and related standards).
Design timber bolted connections to AS 1720.1:2010. Checks bolt patterns under direct shear, in-plane moment, and tension for Australian timber construction.
Design timber beams with multiple spans and load cases to AS 1720.1:2010 (Amdt 3). Checks bending, shear, bearing and deflection.
Design timber truss chords, frame members and rafter ties to AS 1720.1:2010 (Amdt 3), with combined bending, axial and shear checks.
Design timber screwed connections to AS 1720.1:2010. Checks screw patterns under direct shear, in-plane moment, and tension capacity.
