OSB (oriented strand board): wood strands bonded with wax and adhesive, pressed into panels. 7/16 in thickness for wall sheathing and roof sheathing at 24 in o.c. spans. PS 2 or APA rated. Span rating: 24/16 (24in roof, 16in floor). Structural: can be used as shear wall bracing panel per IRC R602.10. Nail pattern: 6in edge, 12in field for shear walls. Moisture: more susceptible than plywood to edge swelling when wet — H-clips required at unsupported edges for roof, 1/8in gaps at panel edges. Weight: ~46 lb per 4x8 sheet. Cost: $12-$25/sheet (volatile — peaked at $60+ during 2021 shortage). CSI 06 16 00. Fire: Class C (treat with fire retardant for Class A). Used in: ~65% of residential sheathing market.