Material selection is sequenced from major (structural and exterior) to minor (finishes and fixtures). During SD, exterior material categories were established (siding type, roofing system). During DD: specific material specifications set — floor finish types, window performance specs, cabinetry quality level, tile categories — with allowances established in the estimate. During CDs: specific products specified or allowances carried for pending selections. Interior design services (coordinated with but separate from architectural design) address finish selection in detail. The critical timing requirement: selections that affect rough-in dimensions (tile thickness at shower transitions, cabinet layout affecting blocking, window specs affecting rough openings) must be finalized before corresponding rough-in work is performed — which is why interior design must be integrated with the pre-construction process, not added after drywall.