In a condo, and just discovered that the floor is actually gyp-crete, presumably over wood. Is a moisture bnarrier necesary? This is above grade.

  • Above grade but is the concrete on the ground? – The Evil Greebo Jun 16 '17 at 12:50

The answer is :

  • It depends

Above grade doesn't mean above ground, necessarily.

If you are referring to concrete that rises out of the ground - then yes, you should put down a moisture barrier. Concrete is porous and moisture will (slowly) permeate the concrete if there's enough moisture around.

However, if the concrete is suspended - a concrete floor above ground with air below it - then no you won't need a moisture barrier.

  • It's a second floor unit – Octavian Jun 16 '17 at 14:40

It further depends on the kind of floor you're installing. Greebo is right about the barrier, but a "just in case" application if you're not sure might still be redundant. Vinyl flooring will be far less adversely affected by water than, say, hardwood. You mightn't need a moisture barrier, but if you're going with hardwood, you'll need to be nailing the floor down. That will mean you need a subfloor of some sort, since gypcrete doesn't hold nails well at all.

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