Brand new home (2700 square foot raised bungalo), been here about one year. Lots of condensation behind vapour barrier in basement. Humidifier turned off, have "two" dehumidifiers going, (for months), cut slits in vapour barrier (will repair when dry), cannot seem to reduce condensation. 1: What causes it? 2: How the @&^%*# do I get rid of it, I want to finish as a family room etc.

It may be condensation or even moisture seeping through the foundation, most likely the latter. This will not dry on its own since the vapor barrier will hold the dampness inside. Do you have a sump pump pit and is there a foundation curtain drain?

I'll go even farther than Bob and say that it is almost certain that it's a leaking basement, not condensation. Call the builder.

There is a sump pump and the pit has no great amount of water. We are on very sandy soil so drainage should not be much of a problem. Spoke with builders rep and he says to keep the windows open on good days and keep the dehumidifiers working, problem should clear up. But going on a year befuddles me. It's not only one area, almost all the walls are wet.

What are the walls made of, block or poured concrete. What is the vapor barrier, a sheet of plastic or the moisture barrier of insulation. Regardless, you may as well remove. If it's just a sheet of plastic it's a problem. If it's insulation its ruined. Builders will say anything. You can pretty much disregard anything they say.

You have a sump pump, can you see the drainage pipe of the foundation or as Bob says "curtain" drain.

Poured concrete. Plastic sheeting over insulation. We've slit the plastic to try and dry it out. Insulation ain't bad, just a little surface moisture. Should be okay when it dries. Cannot see foundation drain pipe, they are buried at the footings.

Should be able to see the ends of drain pipe in the sump crock. Remove the plastic sheating completely.

I agree with HK, you should completely romove the plastic and let it dry out, easy enough to replace later.

Was your plastic applied to the cement or over the insulation? If the insulation is damp or even wet it should get pitched at the builders expense. That builder should be doing this work for you, do not let your warranty expire with this guy.

Given that you are on sandy, well drained soil, the moisture is soil moisture wicking through the concrete. The builder should have sealed the outside of the concrete before backfilling.

In any case, the vapor barrier is a mistake, in my opinion.

Look at the two answers I posted here: (21 and 29, I think)

https://www.askmehelpdesk.com/plumbi...-242374-3.html

They should provide you some insight.

http://www.homeconstructionimprovement.com/basement-wall-insulation-detail/
Check out this link and it will answer your questions and give you advise on moisture barriers. Concrete is full of moisture and will never dry out.

Basement Insulation Detail For Walls | Home Construction Improvement

Go to this website and it should clear up your questions. It is the best I have seen. Good luck!