|Robin E. Snyder|
Post Number: 45
|Posted on Tuesday, May 09, 2006 - 07:17 pm: |
I have always spec'd galvanized finish and I have a request to provide primed cold formed metal framing in lieu of galvanized. The project is in Las Vegas - relatively dry in summers, but pretty wet in the winters. I reviewed Masterspecs evaluations and they state, "Before specifying a nonmetallic-coated (painted) steel sheet, the specifier is encouraged to consult authorities having jurisdiction". Can anyone provide any thoughts and also explain what input the authorities having jurisdiction might have (Why do I need to consult them?)
Post Number: 9
|Posted on Wednesday, May 10, 2006 - 09:40 am: |
The only thing I can think that the AHJ would have to say about a painted or primed finish is that there may be a local ordinance that prohibits certain types of paint or primers (less toxic vs. more toxic). Prior to contacting the AHJ you should have the factory primer info on-hand and if a finish paint is going to be applied you should have that info readily available too.
In addition, just spec'ing a "galvanized" metal really isn't enough. You should specify the type of steel:
(A) CRS: Cold Rolled Steel;
(B) A25 Galv.: .25 oz./ sq. ft. of zinc coating
(AKA galvanneal steel);
(C)A40 Galv.: .40 oz./ sq. ft. of zinc coating (AKA galvanneal steel);
(D)A60 Galv.: .60 oz./ sq. ft. of zinc coating (AKA galvanneal steel);
(E)G90 Galv.: True hot-dipped galvanized steel. This process gives the metal a shinny spangeled-look. The metal needs to be treated to be able to adhere a primer of finish paint to the surface. If the meatl is not properly treated first (etching-process) then a primer or finish paint can easily chip-off.
Also, keep in-mind that CRS steel is less expensive then the others I mentioned above. CRS steel needs to be prime-painted or rust/corrosion will be prevalent. Prime-painted CRS steel (on metal doors) is only prime-painted on the outside...the inside is bare CRS. So, if it's a door, an exterior door, even in LV the product will probably rust (from the inside-out).
The added cost of using A-series metals is from less expensive in the long run because there is no need to prime-paint. You can finish paint directly on the steel because the steel is dry; as opposed to the oil-based CRS which is very messy!
My company, Metropolitan Door Industries manufactures our standard HM doors & frames and our access panels from A40 galv. steel.
|Robin E. Snyder|
Post Number: 46
|Posted on Wednesday, May 10, 2006 - 12:02 pm: |
Thanks Steve. But, I am referring to steel studs, 18 gauge and heavier, in my question. I do spec more than "galvanized metal" - was trying to be brief in my question.
|Anne Whitacre, FCSI CCS|
Post Number: 337
|Posted on Wednesday, May 10, 2006 - 04:07 pm: |
the possible concern of the AHJ regarding prime-painted and/or galvanized studs is their exposure prior to being enclosed and the possibility of rust forming and weakening the members; in some jurisdictions, prime painted is not considered appropriate protection for structural or light-gage structural members. with a painted surface, it would be possible for rust to start at a breach in the paint and then continue to work its way through the stud, unseen; you've probably seen bollards or other steel that is more or less held together by the surface paint. That's the concern and why it was mentioned in the MasterSpec supporting documents. in your climate, its possible that the structural inspectors really don't care what is on the steel, but someplace like the Oregon coast, this would be a pretty big deal.
Post Number: 19
|Posted on Wednesday, May 10, 2006 - 04:20 pm: |
I have worked in Arizona and prime-coated was the norm. We ran into same question as an mentioned where if the stud was the primary structural element it needed to be galvanized.
|Ronald L. Geren, RA, CSI, CCS, CCCA, MAI|
Post Number: 255
|Posted on Thursday, May 11, 2006 - 12:32 pm: |
As I promised you at the Phoenix Chapter meeting last night...
The building code (2003 IBC) does address protection of structural steel in Chapter 22. Section 2203.2 requires that the painting of structural steel comply with:
- AISC Load and Resistance Factor Design Specification for Structural Steel Buildings
- AISC Specification for Structural Steel Buildings--Allowable Stress Design
- AISC Specification for the Design of Steel Hollow Structural Sections
Which one will apply will depend on the steel member and per your structural engineer's advice.
But, to get to your specific question on cold-formed steel, the IBC states:
"Except where fabricated of approved corrosion-reistant steel or of steel having a corrosion resistant or other approved coating, shall be protected against corrosion with an approved coat of paint, enamel or other approved protection."
So, galvanized cold-formed steel per the code would likely be considered a corrosion-resistant coating as well as the painted finish. I think the reference to consulting the AHJ is to determine if there is a code amendment that may have modified this requirement for local conditions. I checked the Las Vegas list of amendments, and this paragraph was not modified, so the painted steel should be accepted by the building official.
|Robin E. Snyder|
Post Number: 47
|Posted on Thursday, May 11, 2006 - 12:40 pm: |
Ron - you are awesome! Thanks! Great presentation last nite as well!
|Mark Gilligan SE, CSI|
Post Number: 78
|Posted on Friday, May 12, 2006 - 01:55 am: |
The focus of the AISC standards is not on protection of the steel. Rather the focus is on the impact of paint on welding, the impact of paint on bolt friction values, or on the commercial obligations of the steel fabricator. The AISC standards point you to the AISC Code of Standard practice (a notorious document) that is focused on defining the work of the steel fabricator.
Bottom line is that if you are concerned about whether you need to paint or the type of paint and its proper execution do not expect to find anything in the AISC standards.
|Robert E. Woodburn|
Post Number: 111
|Posted on Friday, May 12, 2006 - 09:20 am: |
"...AISC Code of Standard Practice (a notorious document)"
"Notorious" for what?
|Mark Gilligan SE, CSI|
Post Number: 79
|Posted on Friday, May 12, 2006 - 11:30 am: |
Notorious for trying to rewriting the contract relationship between the Steel Fabricator and the Owner. For example it states that if you do not find a mistake in the steel shop drawings and the steel is fabricated and installed the Contractor is not liable for the mistake. It states that steel shop drawings need to be returned within 2 weeks of the time they are sent by the steel fabricator which gives the structural engineer 2-3 days to review the submittal if everything works well. I could give more examples.
The CSI MOP had a warning about the use of the AISC Code of Standard Practice. I have not yet found similar languare in the PRM. This is a classic instance of legal language being placed in a standard.
The latest AISC standards including the Code of Standard Practice can be downloaded free from the AISC web site.