Hello, I'm having carpet installed over a concrete floor in the lower level of my bi-level. My question is... what is you opinion (pros and cons) of laying 1/2 or 1/4" subfloor? I'm don't think I would use drilock as it's $$ but was thinking of using plastic (V barrier) with a OSB laying over that. There used to be ceramic tile in this area that has been taken up in case that matters. If you think this would work, how would you go about securing it? Float it, nail it or screw it down? Thanks!!

Why use any subfloor,carpet padding is an insulator and does what it seems to be what your looking for,even out the floor.

Hope this helps,

Ken

You can use carpet that glues directly down to the concrete though if you use the room a lot probably not desirable. You can as KBC mentioned use carpet with pad underneath they make tackstrip especially for concrete application. The only caution I would have for carpet over any concrete is moisture carpet + moisture = mold carpet pad+ moisture equals mold,mold,more mold.

How damp does your current slab get?

Is it above or below grade?

Any moisture problems in the past?

Post back and let me know maybe I can give you a better idea of what to do.

I wouldn't use an underlayments for this, you want find a good way to install that, aside from screwing it down with tapcom screws, and that would take you forever to do.
Carpet on concrete floors still have a carpet tack around the edge.
If you carpet installer say you should install a subfloor... go get another installer there wrong and it's a waste.

Carpet and the padding is all you need

Thanks for the input! The carpet is on order with Home Depot. It is carpet with padding and the padding is supposed to have a vapor barrier on it. The lower level (bi-level home) is half below grade with the bedroom window about 10" above ground level and about 4' from floor to bottom on the inside. There was a moisture problem when I got the home but the house had no garage door on it and the entire lower level was open. Since the door was put up and the walls rehung there seems to be no problem. everything seems dry, however, the paint on the wall seems to stay tacky (not sure if this is the right term to use but it's the best way i can think to explain it). If you touch it you can feel a slight stick as you pull away but this is only in the family room. the other three rooms and stairs right off of it do not have this problem. Not sure if it's the paint or an indicator or hight humidity and not sure why only one room in the same area as others would be affected. At the fire place though there is one very small spot that got moist (not wet) after a very hard rain last year where water was standing at the house but I believe this will be fixed when we grade the yard away from that side. I am worried about mold but I also am worried about comfort and did not want tile in a family room. It's hard enough to say warm with electric heat:) Had I not already finnished two other floors I would have built up the floor with 2x4 and used foam insulation with osb over that but so it goes for me...day late and dollar short. Thanks again for the ideas and keep them coming so I don't come look back and think "I should have done that! "