I really love this floor. It sounds like it was grouted like tile and just sanded and oiled, without a sealer, but for the outside I imagine you'd want to seal it for sure. Maybe the same thing you would use on regular decking?

I wondered if I needed like a wonder board underneath. It would have to have a wood deck sealer because the cross cut would absorb more water and then a permanent sealer on the top? The photo said it used a resin mixture for the grout. I just hate to mess up such a fabulous floor.

You most definitely would need to install it on a cement board substrate. The wood should be pre-sealed with an exterior grade clear sealer until it won't absorb any more. The glue would need to be an exterior grade mastic that will remain flexible after it dries, then grouted with An epoxy grout or a normal exterior grout with an admixture in it to also remain flexible. I would use the same technique inside or out for a durable installation.

Thank you. The house isn't going to start until next spring, and I am not really sure where I am going to use this application, but I love the floor and it will go somewhere, although it will be a smaller application. I would love to do an outside deck, but maybe that would not be a practical use. I might try it on an entry to side porch.
Jan