Hey, I have an older regency r14 insert. After burning one day, I saw there there was a strange cement like deposit of the floor. I went to get it off and chipped a firebrick on the floor. The chip is about 1/4 in deep and 1/2 inch across. I plan on replacing the fire brick soon, but is there any real harm in making a fire before I replace it? Also, does anyone know what size firebrick I would need to use to replace it? I cant find the dimensions in the manual. Thanks