Concrete floor sweating only on painted areas [Archive] - Ceramic Tile Advice Forums - John Bridge Ceramic Tile


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07-30-2010, 11:56 PM
We have a screen room, no windows, which is our back porch.
The floor had been painted by the previous owners apparently a good while back as it had been pressure washed by them many times as evidented by the many streaks off missing paint.
When the weather is humid and going into early spring the floor sweats on only the remaining paint and not at all on the bare concrete. I don't know if there is a plastic barrier under the slab or not.
I have just redone the screening and painted the room and added a ceiling fan.
I wish to repaint the floor and want to correct the sweating or condensation issue.
What do you say?

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07-31-2010, 05:44 AM
I say that may be a good sign.The paint reacts more to the condensation(like a window)and the concrete is soaking in the moisture.The good sign is the concrete isn't wet suggesting water from underneath.I think only more ventilation would correct the problem.

07-31-2010, 07:21 AM
I am going to go with Davestone on this one.

The paint is keeping the condensing watervapor from being absorbed into the concrete so it is wet. Cool surface plus humid air = wet.

Thing is that under the right humidity, temperature conditions, esp in the early morning hours more ventilation will equal more water.

You have a huge thermal mass in that concrete slab and it will need to be slightly warmer, or restrict airflow to keep the water away.

07-31-2010, 08:58 AM
RE:the concrete is soaking in the moisture. I think only more ventilation would correct the problem.

Ok well the bare concrete looks super dry to me while the painted surface is wet. If the concrete is soaking in the moisture, wouldn't it appear darker suggesting water absorption? If I repainted the entire surface I would be in for a real mess of water correct?
There is no cure-all miracle fix is there?
The sealants available only prevent water from wicking up to the surface, and the water present is only coming from the colder air condensing onto a warmer surface. Is that right?:shrug:

PS: Why is that thumbs-down symbol on my post? I don't mean that in any way, only asking for you to spell it out for me. Thanks.

07-31-2010, 10:23 AM
Well, there are a couple things going on,the roughness of the concrete allows for more evaporation than a slick surface as you have more surface open to the air.The concrete absorbs the rest,bit it isn't so much as to darken the concrete.
There is one option,to remove the paint and stain the concrete and leave it.

08-01-2010, 12:32 PM
I think that spells it out for me - staining the concrete, which would still allow for absorption as opposed to paint thus circumventing the puddles Is that right?

So what is the most effient method for removing the remaining paint without making too:scratch: much of a mess because the room is basically finished aside from the floor?

08-01-2010, 01:08 PM
I would either use a scraper,or rent a buffer with carbide embedded screens.They rent the buffers and you buy the screens, they are like sandpaper,you will quickly remove the paint, and also open the pores of the concrete and flatten it.I would use 80 grit for paint removal,and 220 for final sanding of cement.Then i would rinse the concrete a few times to remove everything before staining.

08-01-2010, 01:53 PM
I have a couple large screened porches with SOG floors out there that exhibit the same condensation problem during very humid weather, like when it's raining. Running the ceiling fans minimizes or eliminates the problem. Minimizes if the fans are not turned on until there is visible moisture, eliminates if the fans are turned on before the symptoms are apparent.

Both are known to have vapor barriers under the slab.

My opinion; worth price charged.

08-01-2010, 02:01 PM
Yeah, we get that here,but i haven't noticed it being that bad.Although i don't have a screened porch although i work around them.