Nail Withdrawal Design Value (NDS 12.2.3)
The design number behind the framer's 'nails don't hold in withdrawal' instinct, which fastener-pullout only tabulates.
Example
You enter
- Specific gravity G (0.50 DF-L, 0.42 SPF) 0.5
- Nail diameter D (in; 16d common = 0.162) 0.162
- Penetration into holding member (in) 1.5
- Load-duration factor CD (1.6 wind/seismic) 1
- Toenailed? (Ctn = 0.67) no
You get
- Reference withdrawal W 39.5 lb/in
- Withdrawal capacity 59 lb
Details, formula, and sources
NDS W = 1,380 G^(5/2) D lb/in, times the penetration. A 16d common nail (D 0.162) in DF-L (G 0.50) gives 39.5 lb/in, so a 1.5 in bite holds 59 lb; toenailed at wind duration the 0.67 Ctn nearly cancels the 1.6 CD bump - the reason toenailed uplift is weak and framing hardware replaces it. Side grain only (no end-grain withdrawal). A design aid, not the engineer of record's stamped design.
W = 1,380 G^(5/2) D (lb/in); Ctn = toenailed ? 0.67 : 1.0; Z_w = W x p x CD x Ctn.
The NDS 2018 12.2.3 reference nail/spike withdrawal design value and the toenail factor, by name; the 1,380 empirical constant is named.
The NDS is free to view at awc.org (ANSI/AWC NDS); the 12.2.3 withdrawal equation and the 12.5.4 toenail factor are in the published standard.
Estimate. AHJ and licensed professional govern.
Field names used by the API: g, d_in, p_in, cd, toenail, w_lbin, z_w
- Withdrawal value W = 1,380 G^(5/2) D per inch of penetration into the holding memberNDS 2018 12.2.3
- Toenail factor Ctn = 0.67 for a toenailed connection (12.5.4)NDS 2018 12.5.4
- Side grain only withdrawal from end grain is not permittedNDS 2018 12.2.3.4