Tapcon screws or power loads?

[BB_TX]

When I built my 30x40 metal building, I framed in a bathroom in one corner. I used the power loads to attach the 2x4s to the slab. Marked off the floor, set the 2by in place, then wham, bam, thank you ma'am. Fast. No drilling and then screwing. No concrete blowout that I could detect.

 

[MichMan]

Best way I have ever fastened to concrete was when I finished off my basement, I used 10d galvanized box nails, a piece of bare 12g wire a little shorter than the nail. I believe I used a 3/16" bit and hammer-drilled thru the 2x and into the concrete. Drop the piece of wire in the hole, hammer down the nail, and your good to go. I tried prying up my first bottom plate, to see how it would hold, and pulled the 2x up, leaving the nail in the floor, and a hole in the wood. Cheap, fast and strong. Serge.