Setting a treated sill plate on a new stem wall.

Anchor Bolt Size & Spacing: Use ½-inch diameter galvanized anchor bolts, minimum 12 inches long. Space them 4 feet on center maximum, with one within 12 inches of each corner and wall end (IRC R602.11.1).

Embedment Depth: Minimum 7 inches into concrete (IRC R602.11.1). For 4-inch-thick stem walls, use ½" x 10" bolts to achieve adequate embedment while allowing for sill plate thickness and nut clearance.

Installation Tips:

• Drill ⅝-inch diameter holes in concrete for ½-inch bolts (allow clearance for alignment).
• Place bolts after concrete has cured (typically 7 days for full strength).
• Use anchor straps or holdowns at shear walls and braced wall lines per IRC R602.10.
• Ensure bolts are plumb and properly aligned before concrete sets.

Code Reference: IRC R602.11 (Sill Plate Anchoring) requires anchoring to resist both uplift and lateral forces. Local seismic or wind zones may require closer spacing or additional anchors.

Safety Note: If your area has high wind or seismic loads, consult a structural engineer for specific requirements. Always wear eye protection when drilling into concrete.

IRC R403.1.6 / IBC 1901.3 (ACI 318)

Bolt Size: ½-inch diameter minimum (ASTM F1554 Grade 36 or A307). ⅝-inch is common for heavier loads/high wind/seismic.

Spacing: Maximum 6 feet on center (o.c.).

• Critical: Within 12 inches of every plate end, splice, and corner (IRC R403.1.6.1).
• Seismic D₀, D₁, D₂ / High Wind: Reduce to 4 ft o.c. (check local amendment).

Embedment Depth: 7 inches minimum into concrete/grout (IRC Table R403.1.6).

• Pro Tip: Order bolts 10–12 inches long. This gives you 7" embed + 3–4" for 2x sill (1.5"), washer/nut (1"), and adjustment room for uneven stem wall tops.

Washers: Plate washers required (3"x3"x0.229" min / ¼" thick) per IRC R403.1.6. Standard cut washers are not code-compliant for sill plates.

Layout Tips:

1. Snap chalk lines for plate location before pouring.
2. Use a bolt template (2x4 with holes drilled 6' o.c. + 12" from ends) to hold bolts plumb during pour.
3. Protect threads with tape/nuts while pouring.
4. Treated Sill: Use hot-dip galvanized (HDG) or stainless steel bolts/nuts/washers (IRC R317.3). Standard zinc-plated will corrode.

If: Stem wall is CMU (block), embed J-bolts 15 inches into grouted cells (IRC R403.1.6.2) or use epoxy-set anchors (ICC-ES report required) post-pour.

Verify local amendments—some jurisdictions require ⅝" bolts or 4' spacing universally.