favorite ways to attach 2x4 to concrete basement floors

[Cooler]

The fastest way is with the .22 caliber guns (Ramset).  However my basement was poured with "hardened concrete" which I had never heard of.  The strongest .22 would penetrate about 1/4" into the concrete and I am lucky if I get two holes drilled from each carbide tipped bit.  The blue tapcon screws snap off when I try them with the specified hole size. 

I settled on construction adhesive to hold it in place and a few .22s to keep it from sliding around, plus weights to keep it "clamped" until set.

I have no idea why they would use this type of concrete for a floor.  It is very smooth.  I'm sure that there must be some advantage having it, though it is not apparent.

For most people I think the .22s are best, or the .22s with construction adhesive.

[Gary G™]

I use Red Head or similar in 3/8" diameter 3" long.
I drill a recess with forstner bit the diameter of the washer and depth of head and washer when I need it flush. Otherwise, just drill and go.
Works great.

[rudedan60]

If you decide to use Tapcons, use a rotoray hammer drill.  I have the Bosh Bull Dog Rotary Hammer 7/8".  It is much easier than a hammer Drill, difference is night and day.  4-8 min PC Hammer Drill Old School, to less than 30 seconds.  Vacumn out hole and place stainless steel washer insert Tapcon and screw in.  Don't mess with the screw head ones, get the bolt head. I used 5/16" ones. Dan

[Cub_Cadet_GT]

Ramset, easy peasy. 

[Snipe Hunter]

Usually, I build the walls flat and stand them up and shim them for fit at the joists above. Once plum and in place I nail them up top and drive 2" cut nails between every other stud into the slab, the wall isn't going anywhere. Ramset is nice if you have it but I've got enough cut nails to last a lifetime and as far as I know, nothing has ever moved. I use a hammer to drive through the wood and a small hand sledge to drive into the concrete.

[EricU]

Heh, see my other thread about leaving stuff in walls -- I have a lifetime supply of the cut nails that the previous walls were attached with.  Is it a sign?

[daddo]

Another idea you can make yourself.

[Bob10]

I used one of these before I had the cash to get one of the second.  Both got the job done quickly and depending on which I find first when needing one is the one I use.  The first is probably all you need and both can be found on CL

[srv52761]

......Wear ear protection....

This. After just using earplugs for the first few rounds, I had ringing in my ears, so I went with both earplugs and a good quality ear muff, made a big difference.

Oh, I laid out the sill plate with treated lumber that was relatively dry, used copius amounts of adhesive, then nailed with regular hardened nails from a remington powder actuated hammer gun to hold in place.  Waited a couple of days while I cut the concrete floor to add plumbing. Then built the walls on the floor and secured on the sill plate with a little more adhesive and triple coated screws.

I fully expect the hardened nails have started corroding already but the adhesive is what I anticipated would do the actual securing.

[Foggy]

The old timers would drill a quarter inch hole and drive two 16 d nails into it. they would wedge together.