Should I use a subfloor for a finished basement's floor?
I just recently finished my basement project.  I spent a lot of time scouring the web and grilling friends and co-workers about their basements to gather information to try to make an informed decision on this very subject.  

Here are the options I considered:



Carpet tiles directly over concrete

PROS


cheap


CONS


cold feet
hard, unforgiving floors
Potential for condensation/mildew, even if floor is mostly dry


VERDICT


I couldn't find a tile with a padding thick enough to make the floor even close to comfortable in a midwestern US winter




Traditional carpet and pad directly over concrete

PROS


Pretty cheap
Many choices of carpet and padding thicknesses available


CONS


Floor is still much harder than wood subfloor
Even thick padding can still leave the floor a bit chilly
Potential for condensation/mildew, even if floor is mostly dry


VERDICT


Thick padding can help the floor feel less cold, and less hard, but it's no match for wood, especially if you have a kid's playroom or a workout room in the basement
It seems like asking for moisture/mildew trouble to not allow air circulation between concrete and carpet




Rigid foam insulation under 5/16" plywood subfloor

PROS


Cheap
Good R-value to provide insulation from cold
Feels almost as warm and soft as a regular subfloor


CONS


Opinions vary about how long the foam will last before breaking down
Installation instructions vary wildly (some anchor directly to floor, others anchor through wood bracing, etc.)
Opinions vary about how much air circulation the foam would allow


VERDICT


Although it doesn't seem like a terrible idea, there just wasn't enough information about this approach to make me feel comfortable trying it




DRIcore-style subfloor tiles

PROS


Dimpled underside allows excellent air circulation over concrete
Feels almost as warm and soft as a regular subfloor
Most come in 2'x2' tiles so there are no 4'x8' sheets to lug around
Easy install, much like a "floating" hardwood floor
Nothing anchored into the concrete


CONS


By far the most expensive option
Each 4 sq foot panel is about $5.50 [as of 2016]
USD


VERDICT


I had a fairly large amount of floor to cover, and this was just too expensive.  It would have approached 20% of the total budget for the project.




Dimpled underlayment under 5/16" plywood subfloor

UPDATED March 2019

The Platon underlayment I used years ago seems to be hard to find these days. Home Depot currently offers what appears to be a similar underlayment product called DMX 1-STEP, and others may be available from other manufacturers.

PROS


Dimpled underside allows excellent air circulation over concrete
Feels almost as warm and soft as a regular subfloor
Much cheaper than the DRIcore tiles, because the Platon is purchased separately in large rolls


CONS


More difficult to install than probably any other option
4'x8' plywood subfloor is no fun to lug around
Requires the subfloor to be anchored to the concrete


VERDICT


Although it required more manual labor, the cost was less than 10% of what it would have cost to use the DRIcore tiles
I still got it done in just a few days, with some help moving the plywood
I used a hammer drill and Tapcon concrete screws to secure the floor
My basement floor is as warm and soft as any other floor in my house, and it didn't cost an arm and a leg