you might want to consider using an upcoupling membrane like
http://www.schluter.com/english/products/2002/sectionf/overview-f/section-f.html

good luck

DAC

On Dec 18, 9:01 pm, wrote:
Hello, my house is 5 years old in Florida. I just pulled up some of
the carpet as I plan on starting to lay about 500 ft of tile starting
in the morning. In doing so I found a crack. I am wondering if it is
something I need to worry about or not. It is about wide enough to
slip the edge of a penny into but there is no elevation difference. I
can not tell if it is moving crack or if it has been inactive for a
while.

Should I fill the crack with some sort of epoxy or thinset? Or should
I just tile over it and assume it is not a problem? Thanks.