Painting Structural Steel

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Author Message Mark Gilligan SE, Senior Member Username: mark_gilligan Post Number: 374 Registered: 10-2007 Posted on Sunday, March 20, 2011 - 01:46 pm:    The structural steel specification section, based on the Structural Engineer’s specification, typically addresses the issues of surface preparation and application of shop coat. The two common approaches are either to specify Tnemec paint or one of the SSPC generic paints. Based on the lack of feedback from the Architect I am convinced that whoever specifies the finish paints does not review the painting provisions in the Structural Steel specification section thus leaving the decision to the structural engineer. Structural engineers typically have no expertise with specifying paint. Would appreciate feedback on these specification strategies. Anne Whitacre, FCSI CCS Senior Member Username: awhitacre Post Number: 1134 Registered: 07-2002 Posted on Sunday, March 20, 2011 - 03:17 pm:    This is often a problem and I typically put in extra language in both the structural steel spec that the primer used must be compatible with the finish paint specified in section XXXXXXX AND in the Finish painting section, I put in that the finish paint selected must be compatible with the primer used in section XXXXXXX. it seems like hand-holding, but when I've done this, I never get the "uh-oh" and back tracking to try and coordinate the wrong top coat with the wrong primer. This issue is one of those things that is often only coordinated by the specifier -- its usually off the radar of both the architect and the structural engineer, and unless the structural steel finishing is a "feature" of the finished space, it gets kind of kicked to the "not important " pile. John Regener, AIA, CCS, CCCA, CSI, SCIP Senior Member Username: john_regener Post Number: 519 Registered: 04-2002 Posted on Sunday, March 20, 2011 - 04:27 pm:    Ann: Shouldn't there be a structural engineer's structural steel spec and an architect's structural steel spec so there won't be confusion (!!)? After all, you wouldn't want to mix up design responsibility by including in a single structural steel section such things as recycled content, primer and finish compatibility and finishing of welds (AESS - Architecturally Exposed Structural Steel). Perhaps my concern is misguided. Is there a LEED AP who can explain how interdisciplinary concerns get addressed? John Regener, AIA, CCS, CCCA, CSI, SCIP Senior Member Username: john_regener Post Number: 520 Registered: 04-2002 Posted on Sunday, March 20, 2011 - 04:54 pm:    On a recent project, I had to make sure there was "Tnemec" paint on the exposed steel, including the exposed acoustical decking at the indoor swimming pool. And also I had to make sure the exterior sun control louvers had "Hylar" paint and not "Kynar" paint (the "Hylar" paint supposedly has a different metallic). In the end, I did what I was told ... leaving the construction people to figure it out. At least until the RFI is received and it's thrown my way to fix the specs. Any suggestions about how to avoid these sorts of things by addressing them in the BuildingSmart effort? Mark Gilligan SE, Senior Member Username: mark_gilligan Post Number: 375 Registered: 10-2007 Posted on Sunday, March 20, 2011 - 08:20 pm:    John On some projects there is an Architecturally Exposed Structural Steel specification but this is typically done only when something special is wanted. The trick is agreeing what belongs in what section. This means that people need to talk and coordinate. There is no magic bullet to avoiding coordination. Adding to the difficulty of making a clean separation between architectural and structural specification sections is the reality that the type of paint used can impact bolt slip values. I also want to be involved in the discussion regarding what surfaces are painted and limitations on grinding of welds. Just as engineers feel they must say something about the shop painting architects often feel they must say something about material grades. The reality is that in both cases each party often doesn't know what they are talking about thus leading to potential problems. If individuals coordinate then everything is relatively easy. If there is no coordination then you cannot win. J. Peter Jordan (Unregistered Guest) Unregistered guest Posted on Monday, March 21, 2011 - 10:30 am:    I walked a job a number of years ago where the decision was made to not apply a finish coat of paint to the structural steel. This was an open parking garage in downtown Houston. Apparently, when the painting was deleted from the project, the field touchup of the shop primer was deleted as well. There were what appeared to me to be some serious corrosion issues, aesthetic if not structural. I have attempted to include a touch-up instruction in the steel sections in the hopes that it would not get transferred to the paint section and then deleted. I would like to echo what Mark G. says about Architecturallly Exposed Structural Steel (AESS). This is a special subset of structural work with an almost "furniture-like" finish consisting of very good welds that are ground smooth (almost disappear), no surface blemishes, etc. I usually don't feel like it is worth it for stuff that will be more than 10 feet away from the public eye. On regular structural steel, one can see the "puddle marks" on the welding up closs, but there should be a very consistent width without spatters and gaps. Getting good coordination of the painting on exposed structural work (not AESS work) is difficult enough in the spec writing phase, but it must be followed through in CA. The steel guys typically won't pay much attention to the shop primer, and the person checking submittals has to send it back and be prepared for the howling that follows. We did this for a car dealership, and got the result we were looking for, but not without closely checking the submittals. James M. Sandoz, AIA, CSI, CCS, LEED AP Senior Member Username: jsandoz Post Number: 89 Registered: 06-2005 Posted on Tuesday, March 22, 2011 - 10:02 am:    Mark, I remember years ago a structural engineer telling me 1) it was best not to prime steel that would be receiving cementitious fireproofing only remove loose rust and scale and I can understand the reasoning behind that and I don't see how the Tnemec rep could disagree [grin], 2) this engineer also made a comment similar to yours about slip values and painting which I only superficially understood at the time. You've also made an interesting comment about the limitations on the grinding of welds. I would like to know more about the latter two topics especially. Can you direct me to information that I can share with the architects in my office on these subjects? I would guess that many of them are unaware that there is even a concept of slip values or limitations on weld grinding. These appear to be two topics a local structural engineer could discuss as part of a lunch-n-learn presentation with a title like "What Structural Engineers Wish Architects Knew." I'll have to suggest it to some of those with whom we work. J. Peter Jordan (Unregistered Guest) Unregistered guest Posted on Tuesday, March 22, 2011 - 10:30 am:    I believe the UL designations for spray-applied fireproofing list approved primers. The structural engineer may take the easy way out, choosing not to deal with the contractors' not paying attention to this. I would suggest that in a coastal environment, a compatible primer would save a lot in preparation, well worth the expense. Richard HIrd PE CCS (Unregistered Guest) Unregistered guest Posted on Tuesday, March 22, 2011 - 11:44 am:    Jim: Regarding slip values. There are three types of connections; friction, and two types of bearing, threads "in" or "not in" the shear plane. Bearing connections are not based on load being transfered by the surfaces clamped together. For friction connections only certain paints are permitted on the faying surfaces; inorganiz zinc being one of the paints permitted. Most paints are not suitable. As an engineer I did not use friction connections, which eliminated the problem. Only connections subject to stress reversal, such as bridge framing, significantly benefit by the use of friction connections. Anne Whitacre, FCSI CCS Senior Member Username: awhitacre Post Number: 1137 Registered: 07-2002 Posted on Tuesday, March 22, 2011 - 12:38 pm:    I've done a lot of AESS over the years -- we specify it primarily for the tighter tolerances, since you can specify smooth welds and finishing even on non-A exposed structural steel. The Seattle area structural engineers are used to coordinating with the architects for finishing systems and the local fabricators are pretty used to verifying what we want for primer and finish coats -- and the Tnemec guy is very good at follow-through if you warn him that we're specifying his systems. its a pretty coordinated effort that hasn't worked as well for me in other parts of the country. But.. a couple of coordination emails will go a long way to making sure that even if the contractor isn't paying attention that everyone else on the project knows what the intent is. Mark Gilligan SE, Senior Member Username: mark_gilligan Post Number: 377 Registered: 10-2007 Posted on Tuesday, March 22, 2011 - 02:45 pm:    Jim AISC has a good free publication on AESS that discussed the issues and the relative costs. You want to exercise restraint unless you have a lot of money and the view is critical. http://www.aisc.org/store/p-1500-architecturally-exposed-structural-steel.aspx Shop painting of structural steel is not needed unless you will be applying subsequent coatings either to protect against corrosion or because of visual concerns. Shop painting is not adequate to address any long term corrosion issues and the rust that occurs when the steel is exposed to the elements during construction is not a concern on normal projects. AISC is the source of this information. Spray on fireproofing does not provide corrosion protection normally associated with cast-in-place concrete. So if you are concerned about corrosion and you will be using sprayed on fireproofing you will need to provide a corrosion protection system that is compatible with the fireproofing. Alternately I believe that you can provide a wire mesh around the steel that the fireproofing can be applied to. Coordinate this with the supplier of the sprayed on fireproofing. Richard Hird summarized the main points regarding slip values. When earthquakes are a concern there are limitations on the surface at the bolts even if the connection is formally a bearing connection. This is spelled out in the AISC standards. It is common for structural steel specifications to preclude painting at bolted connections and at welds. Grinding of welds to make them smooth is not a problem as long as the required thickness of the weld is not compromised. This should not be a problem but I have visions of an architectural designer specifically detailing steel weld profiles which could be a concern. Talk to the engineer. Agree with Anne that coordination does a lot to prevent problems. More importantly if you want the structural system to be a part of the architectural statement the architectural designers need to be working closely with your structural engineer. There needs to be some give and take. I have found that cost estimators are not good at estimating the cost of AESS. If you want a good idea of the cost talk to one of the fabricators who will likely be doing the work. Richard Hird PE CCS (Unregistered Guest) Unregistered guest Posted on Tuesday, March 22, 2011 - 10:20 pm:    If you want to know whether the framing connections were designed as friction, the structural drawings should say something like ASTM A 325-F or maybe A 490-F bolts. This is a misnomer because there is no such thing as a friction bolt, just that the design requires friction connections. If it is 325-N or 325-X in lieu of -F it is not a friction connection and any paint can be used between the faying surfaces. Jim Sliff Senior Member Username: jim_sliff Post Number: 40 Registered: 08-2010 Posted on Wednesday, March 23, 2011 - 04:45 pm:    Mark mentions shop painting of structural steel is not needed; I would agree in most cases. In most other cases shop painting of structural steel causes more problems than it "helps" because, as Mark again brings up, the lack of coordination. To clarify one thing - respectfully folks, there is no such thing as "Tnemec Paint". Tnemec is a coatings manufacturer that makes a wide range of primers and finishes, including inexpensive "shop primers" really meant to prevent corrosion during shipping and fabrication - and not meant to be part of the steel coating system (i.e. it's meant to be removed in the field prior to application of the specified coating "system"). So I don't agree with specifying "Tnemec Paint" as a shop primer. I do, on the other hand, agree with specifying the appropriate, VOC-compliant Tnemec (or another manufacturer's) primer. Generally I prefer to see the specified shop primer be the same brand as the finish system for continuity (and in case of failure - an elimination of one finger-pointing source). IMO there needs to be coordination between the Structural Engineer and Architect/Specifier to prevent incompatible systems from being specified; in addition, in many cases it's possible to specify a "shop-applied" primer that simply needs touch-up in the field and prep/priming of welds prior to finish system application. This reduces overall costs as an unnecessary, low-grade "shop primer" (that will be removed - hopefully - in the field) is eliminated completely. Steel fabricators often don't like it, as they are used to their day-to-day inexpensive stuff. Tough. ;-) James M. Sandoz, AIA, CSI, CCS, LEED AP Senior Member Username: jsandoz Post Number: 90 Registered: 06-2005 Posted on Thursday, March 24, 2011 - 10:05 am:    Mark, Richard, and Jim (Sliff), Great information from you all - clear, concise, and, most important, easy for me to understand. Thanks for the AISC link too. Jim Sliff, you bring up a point about coordination between the structural engineer and architect regarding incompatible systems that has aggravated us all at one time or another. I've been fortunate that the structural engineers I deal with are conscientious about this matter. Still it does require us to review each other's specification to ensure compatibility. Honestly, I don't remember discussion about paint/coatings affecting slip in my structures class in architecture school. Keep in mind though my entire exposure was two three-hour classes that included wood (why?) and concrete as well. Further, the class met at 8:00am. Whose bright idea was that ;-) I've been guilty as well of being careless with terms "paint" and "coatings." I believe most of us are aware of the difference but we must be assiduous about using the terms correctly when writing specifications. Mark Gilligan SE, Senior Member Username: mark_gilligan Post Number: 379 Registered: 10-2007 Posted on Thursday, March 24, 2011 - 12:40 pm:    James Given the limited structures coursework that architects have it is likely that they would not be exposed to this fact. In addition these provisions have been added to the code since I graduated in the 70's. The problem is not that architects do not know some detail of structural engineering but rather that they often do not consider the need to coordinate with their structural consultant. Wayne Yancey Senior Member Username: wayne_yancey Post Number: 440 Registered: 01-2008 Posted on Thursday, March 24, 2011 - 12:59 pm:    Mark, I am having one of those "architects do not know some detail of structural engineering but rather that they often do not consider the need to coordinate with their structural consultant" moments right now. Site details include a trash enclosure with a concrete slab on grade with the note "CONC. SLAB ON GRADE, SEE STRUCT DWGS" but nothing on the structural drawings. Also noted for the gate hardware is "CANE BOLT ASSEMBLY - PAINT TO MATCH EPT-1. SEE STRUCT." and for the gate post which is like a bollard "STEEL TUBE COLUMN - PAINT TO MATCH EPT-1. SET STRUCT." I'm in a bad mood this morning. I am having SPECIFIER RAGE and need to take a valium. Jim Sliff Senior Member Username: jim_sliff Post Number: 41 Registered: 08-2010 Posted on Thursday, March 24, 2011 - 02:00 pm:    James - thanks for the comments. Regarding grinding of welds, there is alternative method often used specifically on welds that in many cases provides better results than grinding - pneumatic or electrically-powered "needle guns". They are designed primarily for corners and uneven surfaces. Most painting contractors that do industrial work have them in their "quiver". I suggest not specifying a method but, as is normal practice, specify the desired results and let the sub use whatever method will work. Method should be a field decision, and I'll add this caution - if you specify grinding and it doesn't work, you might end up paying for a needle gun if it's 1) the only way to achieve specified results, 2) you've specified results AND the unworkable method and 3) the painting sub is a commercial painter without industrial tools. I try to stick to the credo of "tell 'em what results you want and let them decide the best way to get there." The caveat - throw in language regarding safety and use of legal tools/methods. But make sure there is field verification of the preparation work *before* any primer is applied - significant future problems can be covered up with a few mils of coating. Mark Gilligan SE, Senior Member Username: mark_gilligan Post Number: 380 Registered: 10-2007 Posted on Thursday, March 24, 2011 - 02:29 pm:    Wayne The problem you mention is a more basic problem. I believe that the PRM talks to this point and the need to verify the documents being referrred to actually say what you want them to say. The phrase "SEE STRUCT" should be banned from architectural drawings as should SSD. As a courtesy I do not use SAD. Depending on where the trash enclosure is it might not even be in the structural engineer's scope of work. I can almost guarantee that the structural engineer will not consider gate hardware in his scope of work. When this gets sorted out the Contractor may very well have a valid claim for an extra. Mark Gilligan SE, Senior Member Username: mark_gilligan Post Number: 381 Registered: 10-2007 Posted on Thursday, March 24, 2011 - 02:48 pm:    Jim Not clear why the needle guns would be a replacement for grinding. The needle guns will remove weld slag which is necessary for good paint application but will still leave you with arough weld surface. Weld grinding can provide the smooth surface. Welders will often use similar equipment to remove weld slag before applying subsequent weld passes. James M. Sandoz, AIA, CSI, CCS, LEED AP Senior Member Username: jsandoz Post Number: 91 Registered: 06-2005 Posted on Friday, March 25, 2011 - 09:18 am:    "The problem is not that architects do not know some detail of structural engineering but rather that they often do not consider the need to coordinate with their structural consultant." Mark, your statement says it all and makes the best argument for why architects and their in-house or consultant specification writers should take coordinating with the design consultants seriously. We can't know even half of what our expert structural, civil, and MEP engineers know. The same can be said for certain specialty disciplines such as elevator consultants. I'm fortuante to work for a firm that encourages its in-house specification writers, and all members of its design teams, to coordinate with our various consultants. Often times this means being in the office well into the evening hours but it is always time well spent and saves grief later. The following comments could be included also in the thread "Who is still using MF95" because they will address comments made there just yesterday about the mechanics of consultants' written specifications. I send out a letter to our consultant colleages at the beginning of each project which explains how our specifications are formatted, etc. along with a sample page. Different clients sometimes require header and footer information be located in particular places on the page. We never have a problem with compliance on this whether an engineer or administrative person actually creates the specification document. In terms of coordination, I do read our consultants' specifications - not word for word but closely enough to see that section numbers and titles match the table of contents, references from one section to another are correct, and that all pages of a section are included. The latter is much less of a problem now with electronic file transfer than it was before with hard copies. I don't get excited when I see sentences written in the indicative mood or certain pervasive grammatical errors such as the use of "their" after a singular pronoun instead of "his." (I've all but given up on that battle.) I do gently point out typographical errors that may cause confusion or words that spell-check doesn't catch like "to" instead of "two." Of course, I trust the technical content of our consultants' written specifications implicitly and I cannot recall there ever being a problem save when the consultant was not given correct infomation in the first place. As it has been throughout my career, the work of the architects and engineers (meaning all consultants) has been done somewhat in separate realms that, if the project is fortunate, gets coordinated sometime before the actual construction takes place. I am hopeful (and must I always be) that BIM and IPD will actually cause coordination among the design disciplines to begin sooner and be more thorough. I apologize for hi-jacking the initial topic of this thread but the subject itself has shown clearly that a seemingly minor matter can have significant consequences when proper coordination is lacking. James M. Sandoz, AIA, CSI, CCS, LEED AP Senior Member Username: jsandoz Post Number: 92 Registered: 06-2005 Posted on Friday, March 25, 2011 - 09:29 am:    By the way, I should add I've learned much by reading the consultants' specifications. They have prompted me to ask questions over the years which have always been graciously answered. I guess others are pleased when someone expresses interest in their work just as I am when someone asks me about mine. Jim Sliff Senior Member Username: jim_sliff Post Number: 45 Registered: 08-2010 Posted on Saturday, April 02, 2011 - 06:24 pm:    Mark - My reference to needle guns was performance-based. In many cases I have seen corners where grinding just can't provide the degree of preparation necessary for a successful coatings application. In lieu of spot-blasting (which is often not allowed or impractical) needle guns can do the job. No, they can't make the surface as smooth as grinding - but in a "pickle" I give the client two choices - a visible weld where the coating will fail, or a somewhat less visible (but not perfect) weld where the coating will probably perform fine. If it *can* be ground that's the way to go. But if it's physically impossible to grind the welds smooth some type of compromise is in order.