18 gauge is 0.048, 16 gauge is 0.060
1/4" diamond plate is way too thick and heavy unless your building a tank or a bulldozer (then again the floor of a bulldozer is only 12 gauge (0.105")
besides being difficult to handle to work into place, your welding 18 gauge to 1/4" which means that your welds will crack in a very short time.
