I am installing 12ml. laminate with underpad to concrete floor in my basement. I have purchased cork sublayment. Do I need to tape the cork together to form one large piece as a barrier against moisture. Please advise.
I would not recommend this approach at all. Use the standard foam underlayment that also serves as a moisture barrier and tape the seams. Even then, be prepared to kiss your laminate goodbye if the basement is at all damp. Tile or polypropylene carpet is usually a better choice. Have you done a moisture test?
Cork underlayment does not provide any effective moisture retarder properties, unless it has an attached moisture barrier film (and I am unaware of such a product). If your laminate has an attached underpad, you may void the product warranty by adding an additional cushioned layer. However, since most flooring warranties are very limited instruments, I doubt that would be a problem for you anyway.