In the next few days we will pour the walls for our walkout basement. Following that, we will apply a liquid waterproofing membrane (a water based one like Tremco Watchdog or Rub-R-Wall). After looking at technical details from Rockwool, and speaking to a sales rep, I came up with a plan to do 3″ of Comfortboard 80 without a dimpled drainage material, because it was my understanding that the hydrophobic nature of Rockwool would allow it to easily drain any water that got to it even without the dimpled layer.

My engineer friend thinks the Rockwool underground will turn into a soaking wet sponge and recommends at the very least the dimpled barrier, if not switching materials altogether to a foam.

I’m a big fan of Rockwool, and maybe that’s why I stubbornly want to make this solution work. We are also planning to use it below the slab, which doesn’t seem to have as much controversy surrounding it.

If I just go with the Rockwool + the dimples, that’s my belt and suspenders, right?