We've removed old ceramic tiles that cover a tongue and groove bathroom floor. What is a good way to remove the hard tile grout that now covers the floor?
EDIT: updated title as we've found Rimu is a podocarp softwood
EDIT: To answer the comment below, yes we would like to finish the boards with polyurethane varnish in keeping with other parts of the house
EDIT: after trying a bunch of approaches what worked was using a belt sander with P80 belts, stubborn areas required a little more pressure
Scraper. This is going to be a tough job if you want to keep damage to the wood to a minimum. It does look like the floor has some type of finish on it before the grout material was applied. This should help a lot to make the scraping removal a bit more practical.
Note that what ever type of scraper that you use will likely need replacement or resharpening a number of times in your removal process.
Buy or rent a pneumatic Air Hammer and get a wide flat chisel attachment for it. The wider the the chisel the faster you can get the job done. If you don't own an air compressor you'll need to purchase or rent that too and don't forget you'll need hearing protection if you go this route.
I've used scrapers before and they do work but I would consider them as the last resort. It takes a tremendous amount of time and energy to use a scrapper and it has to be sharpened constantly to be effective.
Wet a small area and see what that does. Methinks that the thinset is so old that a little moisture will help break the bond to the wood. This won't hurt the wood as long as you do all of the steps and dry it up in a timely manner. I would then half-ass scrape it off. Meaning don't gouge your wood and if a little stays then so be it. Then dry things if it is too wet. Last step would be to follow Herr's advise on sanding...
