Are fireproofing attachment welds covered by AWS D1.1?

Yes. Any weld to structural steel that is part of the structure's final condition — including clips, pins, wire mesh anchors, and studs used to attach spray-applied fireproofing (SFRM) — falls under the general AWS D1.1 framework when the structure is governed by that standard. WPS documentation is required.

Do I need a qualified WPS for welded pin anchors on fireproofed steel?

Yes, if the pin or clip is welded to the structural steel. A prequalified WPS under AWS D1.1 Clause 5 can work for standard configurations on listed base metals. For primer-coated or galvanized steel, a tested WPS addressing the coating effect on weld quality is recommended.

Who inspects fireproofing attachment welds?

The CWI or special inspector assigned under IBC Chapter 17 should verify that fireproofing attachment welds meet the applicable WPS and visual acceptance criteria in AWS D1.1. This inspection is often missed in practice, leading to AISC certification audit findings.

What is the difference between SFRM and intumescent coating attachment requirements?

SFRM (spray-applied fireproofing) typically relies on mechanical bond to the steel surface and may use welded wire mesh or bent bar anchors in thicker applications. Intumescent coatings are applied directly to the steel surface and have no mechanical attachment welds, but the substrate weld quality affects adhesion.

Fireproofing Attachment Welds: AWS D1.1 Procedure Requirements

WPS requirements for clip, pin, and mesh anchor welds attaching spray-applied and intumescent fireproofing to structural steel under AWS D1.1:2025.

Why Fireproofing Attachment Welds Are Frequently Missed

In a typical steel building, fireproofing attachment welds are among the most numerous weld types in the project — yet they appear in surprisingly few WPS libraries and are commonly skipped on CWI inspection plans. The reason is largely organizational: fireproofing is often treated as an architectural or fire-protection subcontractor scope, and the connection to the structural welding quality program gets lost in handoffs.

The practical consequence is straightforward. If a weld to structural steel is required to conform to AWS D1.1 on the project, and that weld is a welded clip or anchor stud used to retain spray-applied fireproofing (SFRM), the fabricator or erector performing that weld needs a qualified WPS and a welder with a current WPQ. IBC Chapter 17 special inspection requirements do not carve out an exception for welds whose function is supporting fireproofing rather than carrying structural loads.

Understanding what types of welds are involved, which qualification path applies, and what the CWI inspection scope should be prevents rework, audit findings, and — in the most serious case — fireproofing adhesion failures traced back to weld discontinuities in the anchor system.

Types of Fireproofing Attachment Welds

Spray-applied fireproofing systems (SFRM) on structural steel typically attach by one of four mechanisms:

Direct bond to clean steel. Thin SFRM applications (up to 1 inch / 25 mm) on properly prepared bare steel often rely on adhesion alone. No attachment welds are involved. The concern here is weld spatter on the steel surface, which must be removed to avoid bond failures, and primer or paint within the fireproofing zone, which must be compatible with the SFRM manufacturer's requirements.

Welded wire mesh or lath anchors. For heavy SFRM applications (>1 inch / 25 mm), or on surfaces where adhesion alone is inadequate, wire mesh is often spot-welded to the steel surface using resistance spot welding or GMAW tack welds. These welds are typically small — 3/16-inch fillet or less — and made on the finished steel surface.

Bent bar or strap clip anchors. Some systems use small bent bars or strap clips bent around flanges or welded to the web to act as mechanical attachment for thick SFRM on beam soffits or wide-flange column faces. These are typically fillet welded.

Headed stud shear connectors doubling as anchors. Where composite deck and beam framing exists, headed studs installed per AWS D1.1 Clause 7 also act as SFRM anchors. These are fully governed by the shear stud WPS and qualification requirements — there is no separate fireproofing attachment issue, provided the stud WPS is in place.

WPS Qualification Path for Attachment Welds

For the most common case — short fillet welds or small GMAW/SMAW tack welds securing wire mesh or clip anchors to bare carbon structural steel — the qualification options mirror those for any other fillet weld in the project.

Prequalified WPS under AWS D1.1 Clause 5 is workable when:

The base metal is an AWS D1.1:2025 prequalified base metal (A36, A572-50, A992, etc.)
The steel surface is clean bare metal or mill scale within the requirements of the prequalified joint
The process is SMAW, SAW, GMAW, or FCAW-G within prequalified process limits
The weld geometry (fillet size, joint type) falls within prequalified configurations

A prequalified WPS for fillet welds must still document all the variables in AWS D1.1 Annex M: base metal grade, process, filler metal classification, position, preheat/interpass temperature, and weld size range. Even if the weld is a minor tack, it requires the WPS on record.

Tested WPS per Clause 6 is required or strongly recommended when:

The base metal is primer-coated, galvanized, or has a shop-applied zinc-rich paint in the fireproofing attachment zone
The steel surface has been blast-cleaned to a profile that affects process selection
The weld design uses a configuration not available in the prequalified joint list

For welding to painted or coated steel, the coating type significantly affects weld quality. Zinc-rich primer and hot-dip galvanizing introduce porosity and inclusion risk at the fusion zone. A tested WPS conducted on representative coated base metal — with visual and NDE acceptance results documented in the PQR — is the defensible qualification approach. Rule library based on AWS D1.1:2025; verify against your governing edition.

Essential Variables That Govern

The essential variables for attachment weld WPS qualification follow the same AWS D1.1:2025 Table 6.6 framework as any structural fillet weld. For a typical GMAW or FCAW-G attachment weld process, the key essential variables that cannot be changed without requalification include the base metal group, filler metal F-number, position (flat/horizontal/vertical/overhead), and shielding gas composition. Rule library based on AWS D1.1:2025; verify against your governing edition.

One variable specific to fireproofing attachment welds deserves special attention: the surface condition of the base metal at the weld location. AWS D1.1 limits the presence of moisture, scale, paint, and other foreign material at the weld joint. If the project sequence requires welding attachment welds after primer application, the WPS and PQR must address that condition — a WPS qualified on bare steel does not automatically cover welding to a primed surface.

CWI Inspection Responsibilities

The special inspector or CWI assigned to structural steel welding should include fireproofing attachment welds in the inspection plan if those welds are structural in nature (i.e., they attach a component to the structural steel member). Specifically:

Pre-weld verification. Confirm the WPS is posted and accessible to the welder, the welder's WPQ is current for the applicable process and position, and the base metal surface condition is consistent with the WPS requirements — especially at painted or primed areas.

In-process inspection. Verify preheat is applied where required by the WPS, filler metal matches the WPS specification, and the weld size is consistent with the design detail.

Visual acceptance criteria. Apply AWS D1.1 visual acceptance criteria: no cracks, complete fusion at the root and toes, weld profile within the limits for fillet welds, undercut not exceeding the applicable threshold. For small attachment welds that will be permanently covered by SFRM, visual inspection before fireproofing application is the only practical window.

Documentation. Record attachment weld inspection in the daily inspection report. Note the WPS number used, welder ID, location on the building, and any rejections or rework. This documentation feeds the AISC certification audit closeout package.

Common Audit Findings

AISC certification audits of fabricators and erectors regularly turn up findings in the fireproofing attachment weld category:

No WPS on file for attachment welds. The project WPS library covers groove and fillet welds for structural connections but has no WPS addressing the attachment weld configuration.
Welder WPQ does not cover the position. Overhead or vertical attachment welds require position qualification. A welder qualified only in flat and horizontal cannot make those welds without separate qualification.
No inspection records. The inspection plan stops at structural connections and does not document fireproofing attachment weld inspection.

These findings are preventable with a one-time review of the WPS library scope at project startup. A brief comparison against the full list of weld types in the project — including attachment welds — identifies gaps before the audit, not during it. For a broader look at the WPS and inspection documentation your audit package requires, see the complete AISC fab cert WPS/PQR audit common failures article and the minimum documentation requirements for a small fab shop welding program. Ready-to-use WPS document templates aligned to AWS D1.1:2025 are available at our pricing page.