This can be done so long as the original floor is a nail/staple in place AND you pay to have the workers work slowly enough that the old floor isn't damaged. You might have to have the finish removed from the old floor and a new finish put on once the ceiling is installed. This will incur extra costs...so be prepared.

Plan on having 10% damage of the old floor during demolition....so re-evaluate the square footage to ensure you will have enough once the removal has occurred. Expect some planks to split or the nails/staples having damaged the tongue groove.

Remember that you are trying to install an expensive flooring product where an inexpensive "decor" product would work. Check the costs of the two products + install to make sure the extra cost/effort is even worth it.

To compare the cost/work benefits: check out Habitat for Humanity to see how much of a tax benefit you would receive if you donated your old floor to them. Then figure out how much a lower grade (thinner) T&G wood product would cost to have mounted on the ceiling.

You might find it more cost effective to purchase the appropriate ceiling wood and have the cost off-set by the tax donation to Habitat for Humanity. Check it out. It can't hurt and it will ensure you "reuse" the old wood floor in the most beneficial way possible. I would hate to see a perfectly functioning wood floor being mounted on a ceiling when the floor could be put to better use in someone else's home.

I've repurposed hwd but not on a ceiling. It is almost not worth it. I'd charge triple to install on a ceiling. It's quite a bit more work and a dyi'r is not going to have the skill set for that. I've repurposed hwd from a huge gymnasium into about 6-7 homes. Tons of extra work just to get the boards in shape to reinstall. After all that then there's the finishing of it....

What about using vinyl plank flooring on a ceiling?