12 mil is good solid material, but it seems to have acquired wrinkles as it was rolled up and the wrinkles hardened into deep, sharp creases that could not be removed. Tried hot air to soften the plastic with little success. As a consequence, it is simply not possible to tape seams securely. Tape can't follow the profile of the creases

Block wall was completely dry and brushed off, but the tape would not stick to it. After attempting for the first 10ft I just gave up and used a caulking instead. It seemed to be more than sticky enough, just wouldn't stick to my concrete block wall.

I have used this product for many years.This is the best material to put in your crawlspace. No vapors will pass through. Be sure to tape your seams.This company has the best price

Well, I bought it twice in a row. What does that tell ya? Good stuff. Good performance.

Sticks well to vapor barrier, concrete block and brick. You should have a roller to firmly press it down into the wall and also to press the vapor barrier onto it. I used the type of roller that is used to install sound deadening material in automobiles. It has a heavy metal wheel with ridges. (Amazon – $10.) I found it easier to drill the holes first, mark the spot where you drilled just above, then put down the tape and the vapor barrier. You can feel where the hole is and punch through with a pencil, then put in the Christmas tree. Which ever way you do it, you must brush the wall before applying the tape. Do not skip this step! Get that dust and cobwebs off there, give the tape a chance to stick. Peel the paper back a little at a time. Apply the vapor barrier carefully, don’t even think about peeling it off and re-positioning it.