I need to know if you need to leave a small gap ( credit card thickness?) gap between the bottom of baseboard and top of solid 3/4 in solid whit oak floors. I know it needs a 3/4 in expansion around perimeter and vertical obstructions, but what about the baseboards? And if so what is the best way to get that gap? Do you finish it off with caulking?
Thank you!

I know my answer is not the proper answer but I'm gonna say it anyway. No you dont have to and the 3/4" perimeter gap is unnecessary also. A 1/4'' gap around the perimeter is fine and drop the base ontop. I would scribe the base to the flooring.