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House is on piers with insulation underneath. We had a plumber come look at it and he says he sees no pipes there, has no idea, cannot help. Every day there is about a 4 ftx4ft area of light water, with outlying smaller patches of water or moisture visible on the plywood. No one lives there while we are renovating.

So, what are the long-term and short term consquences if we place laminate flooring on this large wet spot? My family does not believe my predictions, so perhaps they will believe you.

I do this type of stuff for a living, btw. My paying clients follow my advice. This here is a family thing.

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closed as too broad by DMoore, Niall C., Tester101 Sep 4 '13 at 16:43

There are either too many possible answers, or good answers would be too long for this format. Please add details to narrow the answer set or to isolate an issue that can be answered in a few paragraphs.If this question can be reworded to fit the rules in the help center, please edit the question.

Where do you live? What's the climate like? Is there a roof on the house? Is it raining? What is the temperature swings? Is the house closed in? Are there open windows? – DA01 Jan 9 '12 at 0:03
By moisture, do you mean that there's water sitting on top of the plywood, or is the plywood itself wet? How old is the plywood? – Karl Katzke Jan 9 '12 at 0:11
You should try some plastic (eg 6 mil vapour barrier) over top of the plywood, taped down, which will at least confirm if it's coming from above or below. An intermittent problem that causes a visible pool of water from spraying underneath the plywood seems fishy to me; my gut says it really does sound like a leak from above. – gregmac Jan 9 '12 at 3:06
It's not necessarily directly above. Since you have no explanation either way, it'll at least point you in the right direction, or rule something out. You can do the same on the bottom. Is any insulation wet? Pictures may help. Does it happen every day? Can you figure out time of day? – gregmac Jan 9 '12 at 5:19
I like the plastic sheet idea gregmac has. it would narrow the source down to below or above or from the side. If you are really convinced it is coming from below, pull the nails or screws and lift that piece of plywood and take a look under it. You'll never know what is causing water from below if you don't. DO NOT install any flooring until you have determined the root cause of your moisture, otherwise you are inviting rot and mold. – shirlock homes Jan 9 '12 at 10:47

Sorry im a little confused on what and were your house is loctated? Piers like a beach house over water? The plywood is the floor it's self? Or are you looking at the ply from under the floor? The only thing I can answer is long term will be mold if water continues to sit on ply I wouldn't put any laminate down unless you figure what or were your water issue is and if it is a beach house I will not recomend Laminant floor I would recomend tile.

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Is the area where the water is sitting anywhere near the kitchen...Could it be the fridge leaking?...I'm just throwing this out there because I had a friend, same issue, plumber came twice with no luck finding leaks under the house or in any pipes...turned out, it was the fridge (hooked up for water/ice), it was over 10ft away and somehow the water was trickling down under the flooring and stopping at the spot and building up into a puddle over the top.....

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Is the heat and air conditioning turned on? All houses 'breathe' and draw in moisture as the house cools down at night but will not expel all the moisture as the house heats up during the day. If the house is occupied the heat and A/C and other air from opening/closing doors, windows, etc, will normally eliminate the moisture.

Try leaving a few windows open for a few days to ventilate the house and see if the problem clears up. A couple of fans to facilitate the movement of the air will also help to keep the moisture from gathering in one particular area.

You should also add additional support under the wet area to re-level the floor.

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