Wood Ledger Connection Calculator, NDS 2018

What it checks

The module designs a sawn-lumber ledger connection that is lag-screwed or bolted to concrete, masonry, or a wood-frame wall. It evaluates the connection's ability to carry tributary gravity loads, specifically vertical shear from joists or beams, and optionally checks for uplift via bolt withdrawal. The design method follows NDS 2018 §12, utilizing lateral and withdrawal design values. The sequence of checks begins with the fastener group lateral shear capacity, applying the group action factor Cg where applicable. For concrete or masonry substrates, the main member is treated as rigid, setting Cg to 1.0. The module then assesses bearing capacity under the joists based on the tributary width and load distribution. If an uplift load is provided, the module performs a withdrawal check using the bolt embedment depth and reference withdrawal values.

Inputs

Connection Geometry - Species (dfl, hemfir, spf, syp), substrate (concrete, masonry, wood), fastener type (bolt or lag), and bolt diameter (in).
Fastener Group - Number of bolts or lags in the row, spacing along the ledger (in), and reference shear value Z (lb) for lag screws.
Member Properties - Main member cross-sectional area (in²) for wood-to-wood connections, which is ignored for concrete or masonry substrates.
Gravity Loads - Total tributary vertical shear (kips), joist tributary width (ft), total uniform load (psf), and joist spacing (in).
Bearing Parameters - Bearing length under the joist on the ledger (in).
Uplift Parameters - Optional uplift load (kips), bolt withdrawal reference value Z_w (lb/in per bolt), and bolt embedment into the main member (in).

What it reports

Lateral Shear Capacity - The calculated group lateral capacity compared against the total tributary vertical shear load.
Group Action Factor - The Cg value derived from the fastener arrangement and member stiffness ratios, or 1.0 for rigid substrates.
Bearing Stress - The bearing stress under the joists compared against the allowable bearing stress for the specified species.
Withdrawal Capacity - The bolt withdrawal capacity based on embedment depth and reference values, compared against the applied uplift load.
Fastener Reference Values - The single-shear reference Z value looked up from NDS Table 12C for bolts or provided for lags.

Code references

The engine cites NDS 2018 §12 for wood ledger connections. Specific clauses include NDS §12.3 for lateral capacity, Table 11K for lag screws, and Table 12C for bolts. The group action factor Cg is calculated per NDS §12.3.6. Withdrawal values are referenced from NDS Table 12.2A.

Limits

The module ignores the main member cross-sectional area for concrete and masonry substrates, as the group action factor is fixed at 1.0 for these rigid main members. It assumes the fasteners are arranged in a single row parallel to the ledger length. The withdrawal check is only performed if an uplift load is provided and the fastener is a bolt through the ledger. Results are engineering aids; the engineer of record is responsible for the design.

This module ships in the desktop app

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