What to do with dry cracked grout on floors and fireplaces.

I hate to say this, but if you own the place, consider getting a professional tile setter in to help you diagnose the problem. Perhaps the grout was not properly done when the tile was installed. 1500 square feet is beyond the ability of most do-it-yourselfers.

I would look into a company that sells fireplaces. They may be able to provide some answers. Good luck! I WISH I HAD a better answer for you, dear, but we don't have a fireplace. My friend did, when I was a kid, but she had a professional come out to her place to clean her chimney when needed. Good luck and Google chimney makers in your area. Best wishes for your success!!