Lumber Fastener Withdrawal & Shear Calculator
Structural connections depend on wood density and thread embedment. Calculate pull-out withdrawal strength (lbs) and lateral shear capacity using National Design Specification (NDS) engineering equations.
Excludes head, washer, and attached board thickness
Total screws sharing the load
Ipe (Brazilian Walnut) — Predrilling Guidelines:
Extreme density. Must use stainless trim head screws with full pilot hole and countersink.
Connection Capacity (NDS)
Allowable Pull-Out Withdrawal
1,410 lbs
470 lbs per inch of embedment (2 fasteners)
Allowable Lateral Shear Capacity
676 lbs
Resistance against joint slipping sideways (338 lbs/screw)
• Values apply to sound, seasoned wood with threads fully seated in main wood member.
• Minimum edge distance: 1.5× fastener diameter.
• Minimum end distance: 4× fastener diameter.
Wood Species Specific Gravity & Fastener Holding Ratings
| Species | Specific Gravity (G) | Holding Power Tier | Pre-drilling Requirement | Fastener Metal Recommendation |
|---|---|---|---|---|
| Ipe (Brazilian Walnut) | 0.91 | Ultra-Dense Exotic | Mandatory | 305 or 316 Stainless Steel |
| Cumaru | 0.86 | Ultra-Dense Exotic | Mandatory | 305 or 316 Stainless Steel |
| Garapa | 0.7 | Dense Exotic | Mandatory | 305 or 316 Stainless Steel |
| White Oak | 0.68 | Domestic Hardwood | Recommended | Hot-Dip Galv or Exterior Coated |
| Hickory / Pecan | 0.72 | Domestic Hardwood | Mandatory | 305 or 316 Stainless Steel |
| Hard Maple | 0.63 | Domestic Hardwood | Recommended | Hot-Dip Galv or Exterior Coated |
| Black Walnut | 0.55 | Domestic Hardwood | Recommended | Hot-Dip Galv or Exterior Coated |
| Southern Yellow Pine | 0.55 | Structural Softwood | Optional (ends only) | Hot-Dip Galv or Exterior Coated |
| Douglas Fir-Larch | 0.5 | Structural Softwood | Optional (ends only) | Hot-Dip Galv or Exterior Coated |
| Hem-Fir | 0.43 | Structural Softwood | Not required | Hot-Dip Galv or Exterior Coated |
| Spruce-Pine-Fir (SPF) | 0.42 | Framing Softwood | Not required | Hot-Dip Galv or Exterior Coated |
| Redwood | 0.38 | Naturally Durable Softwood | Optional | 304/316 Stainless or Cedar-rated |
| Western Red Cedar | 0.32 | Naturally Durable Softwood | Optional | 304/316 Stainless or Cedar-rated |