I have a concrete porch that is about 8″ thick and whenever we have a humid day the porch looks as though I had turned the warter hose on it. I know that plastic was installed on the ground before the concrete was pored because I was there when it was instaled. When the humidity goes down and the weather is better the water, within a half day, is gone and the porch is dry again. Does anyone out their have any suggestions. I am going to screen in the porch but do not know if that will help or not.
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Sounds like condensation.
Cold concrete, warm humid air.
Not much that can be done that I know of.
Certainly it's condensation, so the only thing you could do is put a waterproofer on it to keep the water from absorbing into the concrete. Any condensation would then sit on the surface. In a cold enviroment this might cause more of a problem than it cures by freezing on the surface. I think you are probably better off not doing anything. Using salt or CaCl in winter seems to cause more absorption of water making the problem worse, and eventually cause spalling.
If you follow the advice to put waterproofing on it, be careful about slipperiness--I worked where there was an epoxy coated concrete floor in the garage and in the summer when humidity condensed on that, it was like an ice rink! Would be simple enough to add silica (like they use to make paint non-slip) to any coating you put on.
Edited 2/10/2008 3:49 pm ET by Danno
Thanks for the reply to my question. I had painted the porch several rears ago but got tired of fighting the moisture. Do you have any suggestions on how to keep the moisture from condensing on it all?
I don't think there is any way of preventing moisture from condensing on the concrete--other than expensive things you probably would not want to do--heat the concrete (especially not something you'd probably want to do in hot, humid summer!), or enclose the space and run air conditioners or dehumidifiers to remove moisture from the air so there's no moisure left in the air to condense on slab. Using fans to blow the air over the slab may help slightly to keep moisture from condensing.
Oh, you might try thick fiber mats or carpeting or rugs--those would sort of insulate the slab and if the slab did get damp, you wouldn't be slipping on the dampness because of the carpet being there--get something like indoor outdoor that can take some dampness without mildewing and smelling. The principal here is the same as insulating the outside of a toilet tank with a rug- or towel-like cover; the cover keeps the warm, moist air from direct contact with cold tank. Carpet would do same thing with concrete floor.
Thanks for the suggestion.
Hang a ceiling fan over the slab. Run it when there's a problem.
Probably not what you want to hear, but warming the concrete will eliminate your problems. A bit of a problem to get the heating coils, electric or hydronic, into the concrete after the fact.
Beer was created so carpenters wouldn't rule the world.
Radiant heat lamp mounted above the porch?
They can't get your Goat if you don't tell them where it is hidden.
Riversong will getcha for that!
;)
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