SSPC Blast Standards and How They Appear on Drawings
Surface preparation is specified using SSPC (Steel Structures Painting Council) standards, referenced in Division 05 of the project specifications. The detailer documents the blast requirement on the shop drawing general notes or the individual member callout.
- SSPC-SP3 — Power tool cleaning; minimum for industrial environments
- SSPC-SP6 — Commercial blast; most common structural standard
- SSPC-SP10 — Near-white blast; required for high-performance coatings and aggressive environments
- SSPC-SP5 — White metal blast; specified for immersed or extremely corrosive conditions
Paint and Primer Callouts
Paint callouts on shop drawings reference the specification section (typically 09 90 00 or Division 05 notes) and state the primer type, number of coats, and dry film thickness (DFT) in mils. Members that will receive spray fireproofing are often left with bare-metal primer only; members exposed to weather receive a full coating system. Members in contact with concrete are typically left bare or coated with a specific bond-compatible primer.
Bare Steel Zones for Field Welds
Field weld zones must be left bare — uncoated — for a minimum of 2" on each side of the weld joint per AWS D1.1. This is one of the most frequently missed items on shop drawings. If a column splice is field-welded, both the column and the splice plate must have bare zones at the weld joint called out explicitly. Inspectors flag painted field weld zones as a nonconformance; removing paint and re-blasting in the field is slow and expensive.
Galvanizing Callouts and Their Special Requirements
Hot-dip galvanizing per ASTM A123 is a complete surface treatment — not just a coating over blast. When members are specified for galvanizing, the shop drawing must include: a note referencing ASTM A123 and the required minimum average coating thickness (typically 3.0 oz/ft² for structural shapes); vent hole locations in closed sections (HSS and box columns require vent holes to prevent steam explosions in the galvanizing bath); and drainage hole locations for members that would trap molten zinc. Detailers who specify galvanizing without noting vent and drainage hole requirements create a shop problem — the galvanizer will either return the member or add holes without documented approval.
Multi-Zone Coating Requirements
Many projects require different coating systems for different members depending on exposure: interior structural members may receive a single coat of rust-inhibiting primer; exterior exposed members receive a full three-coat system; embedded or buried members receive a coal-tar epoxy or zinc-rich system. Shop drawings on these projects must clearly identify which coating zone applies to each member — through a combination of drawing notes, zone callout blocks, and member-by-member callouts for exceptions. A drawing that specifies 'paint per spec section 09 90 00' without identifying which of three specified systems applies to this member is functionally incomplete.
Special Inspection for Coatings
The IBC and project specifications may require special inspection of surface preparation and coating application — not just of structural steel connections. Special inspection of coatings typically covers: blast profile measurement (surface anchor profile per SSPC-PA 2), dry film thickness measurement per coat, and holiday testing for immersion-service coatings. When coating special inspection is required, the shop drawing should note this requirement so the shop can schedule the inspection agency at the appropriate step in the coating process — not after the full system is applied and individual coat thickness can no longer be measured.
Documenting Coating on the BOM and Reporting
Tekla Structures can generate a paint-area report that lists the surface area of each member — used by the coating subcontractor to verify quantity and by the project manager to estimate coating costs. The report calculates exposed surface area from the member's cross-section geometry and fabricated length. However, the report does not automatically account for coating zones unless the model is configured with zone attributes. For accurate zone-specific reporting, each member must have its coating zone assigned as a model attribute — a setup step that takes minutes per member and saves hours of manual calculation on large projects.