The point of frameworks like Foundation is two-fold. First, you can use the built-in grid classes (“column-4” and so forth) for rapid prototyping, and they’re also useful for content managers who just want some nice columns without needing to worry about the CSS. Secondly, if you’re using Foundation (or whatever) for a production-quality product, you should be using the SASS/LESS mixins anyways, exactly the same thing you’re describing above. This is technically the “correct” way of using these frameworks — the “column” and “row” classes are just defaults and aren’t meant to be kept. There is absolutely no need for the grid classes to exist in a Foundation project if you don’t want them — just disable them in the settings.scss file and use the grid mixins instead.