What is the recommended overlap for plastic (6mil) sheet, and what should I use to tape the edges together? Is duct tape ok?

Also, is it worth doubling the layers of plastic, or is this overkill?

Additionally, what direction should the seams of the plastic sheeting be traveling (parrallel or perpendicular to the direction of the wood flooring?

After pulling the old rug off the floor, I can see the floor is nicely flat and level, but there are 3 cracks. Two of which are hairline, one which is about a 1/16 of an inch wide. Should I do something about these cracks, like silicone, or will the vapor barrier take care of that?

I am testing the concrete in 4 places (2 tests each on 2 exterior walls). It's a 3-day test I bought from Lowes called "precision moisture vapor and Alkali test kit". I am currently running the first test ... moisture test. The second and last test is an alkali test, which shows a low ph (#3 or orange in color, on a scale which goes to #13 or purple)

So far, the moisture test (after day 1) is still a #1 on the test kit color, of which the scale goes to a #5 or pink.

Thanks for your help,
Gino.

Duct tape is fine for the seams of plastic. What kind/type of floor are you installing?

I have almost purchased it, but not yet (Wife still deciding). It will either be an engineered hardwood, or a quickstep product. She is leaning towards an engineered hardwood (Kahrs).

Doubling-up the plastic ... overkill?

Clear packing tape is better to use, then cloth duct tape. I've seen duct tape break down(not on a moisture barrier under a floor)


Over lap 4 inches at least.

Looks good and flat, has cause many failures!! How did you check to see if it was nice and flat?

Stretch a string tight across the surface of the concrete in all directions, and then tell me it is (1/8" in 6')

Or an 8' to 10' straight edge. You'll be crying the blues, if you find out after the installed floor is in, that the concrete was not as flat as it should have been.

I have yet to see a concrete slab, that didn't need at least one low spot filled.

Thanks Floorguy. I did not do that test, I eye-balled for bumps. I will check that with a string.

Did you have a recommendation for the direction of the plastic sheeting? or if I should just double it up.

Thanks for the wrapping tape tip.

BTW, it's been three days, and the moisture test in the 4 locations are the same color ... purple.

Does anyone have a tip for the cracks? Leave them alone?

Thanks,
Gino.

Tape down a 2 foot square of clear plastic, to the concrete in several locations, throughout the installation area.

Look for the concrete under the plastic to change color to a darker gray, which is bad. Even worse is when water droplets appear on the plastic, itself.