Are you looking to cover it or spray something on it or fill it with something to keep the original shape?
Why not just enclose it in a 2 hour rated enclosure? Something like steel studs with two layers of 5/8" drywall should be enough, but you must verify that with the UL details.
The cast iron column is in what will become a parking area. It is round with a tappered base plate. It would be difficult, but not impossible to cover in studs and gyp but I am trying not have to do anything if it isn't necessary.
The column is about 1-1/2 inches thick wall, and about 24 inches in diameter. It would take one hell of a load to do anyting to it. It is supporting a 12 story building.
That's a horse of a different color! I was thinking of a 6" or 8" column at the interior of an office or commercial building.
You will definitly have to fireproof it and if you think about what you see in other parking garages I would bet you are looking at spray-on fireproofing, concrete or masonry enclosure. What does your local building code offical say? Have you looked for approved UL Listed Assemblies in the UL book? You could also call Underwriters Labs and talk to someone in their techncial services department, although you might have to subscribe to their service to get a written answer.
UL was called last week, but of zero help. All of there assemblies are for steel, not cast iron. I don't know very much metalurgy, but I do seem to recall that Cast Iron will act very differently to heat/flames. I was trying to avoid doing anything to it but conservatively we would just to cover ourselves. Right now we are persuing the building code official to hear what their verdict is but they would likely follow our recomendation if we had one.
Thanks for the help.
Just a thought, but take a look at filling the 20" diameter cast iron columns with concrete. Would a plain, unreinforced column 20" in diameter carry the column load if the cast iron column melted away? What percentage of the total column load would the added weight of the concrete be on the supporting footing? I'm again ASSUMING (I hate that word) that this is the lowest level.
You could make a reasonable argument that the column is protected in the unlikely event of a fire and yet the cost wouldn't be that great, the cast iron column would be the form for the concrete.
Good thought jheidt, but the walls of the cast iron are between 1 1/2 inches and 2 1/4 inches (this I get from a 1930's design guide for round cast iron columns. I would say it is very difficult to open a sufficient hole in the columns (our contractors guess is that would be about a 4-6 hour hole for an iron worker to create.
Unfortunately I'm really outside the box on this one. The building code official has been little help - he said its not combustable and therefore doesn't need to be protected!
This is a car parking and cars burn as you can see in any Hollywood movie. Sometimes, in real life as well and the authorities are not doing justice to their jobs if they say no protection is required.
One option will be to embed the entire column into concrete. This can be done by wrapping wire mesh around the existing column and then plastering with air entrapping concrete. The mesh should be able to act as reinforcement and hold the concrete layer in place. Though I do not know how practical it will be in your case.
Be sure and isolate the cast iron from any mesh or rebar to avoid corrosion problems (galvanic cell.) A high quality epoxy paint should do the trick; other methods can also be used.
Please see FAQ731-376 for great suggestions on how to make the best use of Eng-Tips Fora.
The saga is over. The city has finally ruled and they want 2 hr intemecent (spelling horrible) paint to cover the column at a minimum. I will leave that up to the fire-proofer to come up with the proper quanity/thickness of paint to do the job.
Thanks for all your help.
Intumescent paint is a simple solution, one of those "Why didn't I think of that!" things. The nice thing about it is you still get the "historic" look of the cast iron columns.
I've never used it, but have seen it specified on a job I quoted. It must be fine, I just find it unsettling that a thin paint film will meet a two hour rating. "Intumesce: to swell, enlarge, expand or bubble up. as with heat" from the Webster's New World Dictionary.
dougantholz, please post a note on the product that is finally chosen.
Cast iron melts sooner than mild steel. No kind of paint will act as insulation and prevent the column from melting. These paints are possibly good for combustible material as they will stop the material from catching fire.
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