My wife and I bought a 8 year old log cabin last year that needed a lot of work. Currently we are trying to redo the floor for our loft. The flooring is 2 x 8 T&G yellow pine and was nailed and glued to the rafters (which are 4" x 8", 32" on center). The reason we are redoing the floor is because just about all the boards either bowed up or cupped and there are up to 3/8" gaps between the boards (the tongue and groove separated).

At this point, we have taken down all the flooring and put it through a planer to get the boards flat again. Now I am trying to figure out what to do with the tongue and groove in order to get them matched up again. My thoughts are to increase the width of the groove and then use felt/tarpaper to wrap around the tongue so when I put the boards back together, I will get a snug fit with no creaking. Any thoughts would be greatly appreciated. Also, I'm thinking that nailing/glueing the boards back on to the rafters is a bad idea (at least the glueing part). I was going to countersink 3" screws on the tongue side. Would this be an acceptable way to anchor the floor back to the rafters?

As for starting installing a new floor... this is not an option at this point - we already put waaay to much into this place!

Thanks in advance!

I would not make the grooves bigger, and work with what you have. It is pretty common to have issues with planks this wide cupping. I would glue and nail it. For the glue I suggest Bostiks best. If the cabin is not heated in the winter you could have issues with the floor cupping again. So if possible I would make sure you run the furnace.