Rusted galvanized steel decking under concrete garage floor
I’m desperately trying to find an answer for a rust problem I’m having underneath my steel decking in our garage. I built a house in 2001. Instead of the conventional poured concrete garage floor over compacted substrate, we opted to have the contractor dig out the area completely, reinforce with steel crossbeams and galvanized steel decking and pouring the concrete over the steel, thereby giving us more useable space underneath the garage. The problem is that in the past year, we’ve developed a serious problem with rust and possibly zinc oxide (white powder) that is all over the underside of the steel decking and now starting to fall off onto the floor below which is creating quite a mess.
We’ve had some local contractors over to look at it and none were willing/able to offer suggestions as to where to turn or what to do about it. So now I’m getting desperate as to who I can turn to for help. I’m hoping someone can point me in the right direction.
I’ve attached a photo to give a better visual on the situation.
Replies
Is this purely a cosmetic/housekeeping problem, or is it structural (or threatening to become structural)?
Presumably you have the corrosion either because humidity condenses there (likely coming from the earth below), or because water works its way down through the concrete. If the latter, and if any of the water contains salt, you could have a serious problem -- I know of several buildings around here where they had to tear out and redo the floor (built like yours) near the entrance because pedestrian traffic tracked in salt and it corroded through the steel.
If it's basically cosmetic, and the problem is caused just by humidity from below, then the obvious thing to do (other than to control the humidity) is to prime and paint the steel.
Cosmetic or Structural???
Dan, thanks for the response. I'm not sure if it could become a structural issue or not although I'm guessing it could. I have cracks in my garage floor and I can almost guarantee that those cracks are allowing water/salt from winter travels down through to that steel. We are located in PA so we're stuck with winter driving and salt.
So I guess it is probably cosmetic now but if I don't do something about it, it will become a structural issue as the salt begins to eat away at the concrete AND the steel.
You need to seal the floor somehow.
Let me know what you come up with.......
I have a customer down the street that I swore you took your picture at his place.
His floor has no visible cracks, but he thinks salt's been seeping down the control cuts (hence the cracks are there, tho unseen and "controlled". I filled my saw cuts with urethane self leveling caulk which may have kept the salt sludge out of the slab, too bad they didn't
You need to get a Structural Engineer involved now.
I'm assuming that this was engineered to begin with. Don't go back to that Engineer, but get an independant one involved. And the new Engineer should either be specialized in Structural or Forensic Engineering, you should be able to find one in the yellow pages.
This would seem to be a design error/ommission, and the original designer may be liable for the cost of repairs.
Just guessing, having not seen either the design drawings, or the actual structure: But, there is most probably structural damage already. If the steel deck is in that bad of shape, the reinforcing steel is probably in worse shape.
Rusted ceiling under garage - severe!
Looking for ideas on a severly rusted ceiling under garage...house is almost 50 years old, room under the garage is unheated. We had a structural engineer an a builder check this out before buying, and both thought the structure was sound. But, tons of rusted pans under the concrete. I've started chipping away the rusted pans, exposing just ocncrete in some areas, and some parts of concrete have broken off (end pieces of wedges formed in the corrogated metal).
I was thinking continue removing as much rusted metal as I can, then getting a painter in to spray it with something to prep it for a top coat of a more finished paint.
The garage floor is sealed, but the house is old, and rust most likely from inside condensation (according to inspector/builder and engineer).
Anyone ever deal with this sort of "project"? (successfully) Any ideas, thoughts, or concerns? Pics below if I was able to attach them.
I doubt that it's just condensation -- more likely salt soaking through. One way to tell is to observe where the rust is worst. If it's under where the salty winter car would park then it's due to salt.
Simply having the floor "sealed" is probably not doing much good. It would need to be essentially plastic-coated to prevent this.
Thanks Dan. Clearly there are areas that have less rust - almost no rust on the edges. By plastic coating do you mean tiles or a roll-out mat (instead of epoxy coating)?
Now I'm wondering about the rebar...sigh.
I'm thinking a thick epoxy/rubber coating of some sort.
And, yes, the rebar is suspect. But generally one would expect to see signs of trouble (cracking and sagging) before a complete collapse.
(Note that you can tell a lot by the condition of the top surface of the concrete. Where salt has been a problem the surface will usually be spalled quite a bit.)
Did you find a solution to your problem? Our house was built in 2001 and both the steel trusses and the galvanized steel decking show a lot of rust underneath the upper garage slab. I don't know where to turn for a solution. TIA
Folks,
This has the potential to be a big structural issue. Metal decking can be used simply as a stay in place form to pour the concrete over in which case the concrete deck is the structural component and the metal serves no structural purpose after the concrete has cured. But sometimes the concrete and metal deck are designed to act in tandem this is called a composite slab. With a composite slab corrosion of the metal pan is a serious structural issue.
Get off the internet and find yourselves a structural engineer.