Deck installed on grade

Is it a good or bad idea to install a vapor barrier underneath a grade/ground level deck?


Some contractors install plastic/vapor barrier to keep the weeds and grass from growing up through the deck.


Doing this will trap moisture. The best method for installing a deck on grade would be to remove the earth in the area, lay down landscaping cloth, a bed of crushed stone and then the deck.
The cloth and stone will allow drainage and keep the weeds/grass down.

No plastic under decks, please…When it rains the moisture will now accumulate on top of this plastic and the deck structure will become compromised and will eventually rot away, because this concealed moisture accumulation will not evaporate quick enough.

Crushed stone is the norm in my area. This stone will always remain dry, because it drains.

We put down landscaping cloth covered with stone for our new deck.



So if thats the case…why would you also allow the raw lumber in a few places in the pic that I see be in contact with soil???

I took care of that with 1/4" chicken wire for separation, air flow and to keep critters out. Also installed deck boards to make it easier to get around on the deck.:p:p