Depending on the color your going with on the exterior, if you keep it red or another darker toned color, I'd go lighter almost honey on the floors; knotty pine? I have always wanted to redo a barn into a modern/rustic home!

I have just taken a couple more pictures (excuse the untidy house) from the stairs. As you can see it's an open plan area that isn't that big but very high ceilings also in wood (Macrocarpa) with dark wooden beams. The house is surrounded by bush so quite a dark house. I initially considered a darker wood similar to the beams but not sure if that will make the house appear smaller / darker...I'm really not sure what to do!?!?!? Thanks

Do you want to keep the wood floor? It is rare to see wood floors as garage floors. I've seen homes like this moved onto pour basement slabs (same concept as pile foundation...but with a basement instead of dirt. If you want to keep the wood, then there has to be a way to keep the wood off of the concrete. An 18" crawl space (dirt covered with 6mil poly sheeting or cement) is always an option. The 18" crawl space would have to be cross vented/heated properly. This is for "keeping" the wood. Flooring. I'm not sure what has to be done to remove the wood floor and have the building sit (joists and all) on concrete. Remove the joists and you have plenty of stability problems. You would need to speak with a local architect/building engineer who has some knowledge of what you are trying to do, soil conditions, etc. to get this right. In theory it can be done (we've just landed a small car on a comet...we should be able to put an old building on a cement slab)...I'm wondering about the expense to get it there (excavation + soil stabilization + concrete + piles, etc).

I think it would make both rooms too dark. Maybe go with a lighter floor colour?