What is the purpose of foundation anchorage in a wood-framed house?

Foundation anchorage exists for the loads that try to move a building rather than the load that presses it down. Wind produces uplift on the roof plane and lateral pressure on the walls; seismic events shake the base horizontally and cyclically. Anchor bolts, with their washers and nuts, tie the sill plate to the concrete so those forces transfer into the foundation instead of sliding or lifting the structure off it. Gravity needs no fastener at all — the framing bears directly on the plate and the plate on the wall, and weight travels down through contact. Keeping the two straight matters in practice because it tells the inspector what to check: full bearing for the gravity path, and bolts with washers at correct spacing and end distance for the anchorage.

Anchorage resists uplift and lateral displacement from wind and seismic loading. Gravity load is carried by direct bearing of the framing on the plate and the plate on the wall, needing no fastener.

Sill plate anchorage transfers lateral and uplift forces between wood framing and the foundation, using bolts at specified spacing and within a set distance of plate ends and splices, with washers and nuts drawn tight.

Weight Presses, Wind Pulls. Bearing handles the pressing; bolts handle the pulling and the sliding.

Check for washers under the nuts. Without them the nut can pull through the plate under uplift, which defeats the anchorage while looking correct.

• •Assigning gravity load to anchor bolts
• •Confusing anchorage with grounding or moisture separation
• •Confirming bolts are present without checking washers and end distances