I am currently in the process of finishing an unfinished basement, my problem is that occasionally the basement floor is damp. I have inspected the basement and there are no cracks in the walls or floor (solid concrete walls). My plan is to use a ceramic tile on the floor and was wondering in anybody knows of a way to seal the floor to prevent this sweating, and will this sweating hae an effect on the tiles?

Thanks for any help.

Sealing the floor will likley not help.

The problem is likley caused by the temperature of the concrete being below the dew point of the basement air for its relative humidity.

You will do best to seal the walls with a vapor barrier paint such as DryLok and use a dehumidifier.

Sealing the floor with a vapor barrier coating won't hurt, but most modern basement floors already have a vapor barrier installed under the slab.

homebild's statements seem reasonable. If you are not using a dehumidifier, then I agree with homebild that would be something to try. Is you house relatively new? homebild pointed out the most modern houses have a vapor barrier installed under the slab, and that is true, except in cases where the slab was at one time a garage floor. I have inspected a house in Tennessee that had a severe mold problem. It turned out that the owners had "taken in" the original garage to make it into a bonus room/family room/office space. They installed wood flooring over the slab, but the flooring started to buckle and mold started to grow in the area inside closets and other undisturbed and unventilated places. It turned out that the former garage slab had no vapor barrier.

The house is about 70 years old, so I have no idea if there is a vapor barrier installed under the slab. The floor is a full basement and has never been used as a garage floor. I think I will give a dehumidifier a try and hope that solves the problem. Any other ideas would be appreciated and thanks for your help.

If the house is over 70 years old, there almost surely is NOT a vapor retarder under the slab, and if there is (was), it has long since deteriorated. Modern plastic film vapor retarders did not come into consistent use until the 1950's and '60's.

I would re-consider putting a tile floor in your basement if you are in an area of the country that gets cold winters. Reason is in the winter you will never walk around in your socks down there, and if it becomes cold enough it could freeze and buckle the tile. My suggestion is to purchase flooring with some type of subfloor built in. Nothing organic it your will have mold.

With the house being 70 yrs old did you consider using the Drylock on the walls and putting a poly vapor barrier over the existing concrete slab and then pouring another slab over the old one?
jw

cellar dwellar, I was just curious as to what type of flooring has a built in subfloor? I've seen a product at home depot thats a press board with a hard plastic bubble system on the bottom, has anybody ever used this product?. Another option I was thinking of using is a laminate wood floor but I'm not sure of the underlay for it would protect from any amount of moisture. As far as laying a vapour barrier and pouring an additional slab over top, I think thats a little more expence than I want to get into for a basement rec room. Thanks to every body for their help. Any other suggestions would be appreciated.

P.S. I have been using a dehumidifier down there for a couple of days and it has made a drastic improvement, I'm wondering if I should take the opprtunity and apply a sealer to the slab while it is dry?

Chrisj: There is a pretty detailed waterproofing myth-busting post on the website by LicensedWaterproofer. Many of his statements make a lot of sense. His experience reinforces the training and (unfortunate) personal experience I have had with leaking basements. If you try to seal against moisture intrusion from the inside, you are fighting a losing battle. The ground water pressure is working against you. Using the dehumidifier is going make your life easier and may assist in protecting moisture-sensitive materials and storage from damage, but you may only be treating a symptom, not curing the disease, like taking aspirin for a broken leg -- some of the pain will go away for a little while, but it will come back sooner or later and with greater impact. If the source of your moisture is truely from condensation, then running a dehumidifier is basically your only option short of installing HVAC supply and return ducting in the space. If your basement's air is already being conditioned by your HVAC system then I would investigate whether there is adequate supply AND return from the space. If not, or if central air conditioning is not installed in your location, then the dehumidifier is your best bet.

If there is adequate HVAC supply and return and you are still getting moisture across the floor, I would suggest the source of moisture is exterior and not humidity related. In that event, further analysis by a local contractor might help you locate the source and take steps to deal with it from the exterior. Again, interior sealing against ground water pressure is at best a temporary solution.