Many thanks for the advice,
-Ben
How large is the space?
1/8 or 1/4"
Grout is good. Silicone caulk is better.
1/8 or 1/4"
I'd probably use grout but why did the existing grout come out? How did you
discover the space? If the grout came out because of movement of the jam
it's just going to come out again. You might need to use a harder compound
and find a way to nail the jam down. Jams move sometimes because they are
not installed properly and cause the grout to crack around them. If the jam
moves when you step on it there could be a space underneath that needs to be
filled. I'm just guessing from personal experience. Otherwise, if the jam is
secure just use grout or any compound. I like to use Household Putty (Bondo)
in difficult spots but it can come out too. Another way could be to cover
the space with a piece of threshold material.
I was going to say caulk but if it's in an area that collects dirt or gets a
lot of traffic I would use something else.
If it had been filled with grout, there should still be plenty. Perhaps
it was just neglected.
We have grout between out tile floors and adjoining terazzo floors with
no cracking or
crumbling. Sanded grout. Or, if reasonable, a different threshold
which bridges the gap.
I would try to find a silicon grout that matches your sanded grout as they
are more forgiving when separated my two different materials. I have no
personal experience with them but have seen them used on home improvement
show where a tile mosaic met up with a hard wood floor. They apparently have
the same colour sand in them and look very much the same as the sanded
grout.
I have been in my house for 2 and 1/2 years and still have not filled a few
spots on the edges of my door frames where the previous owner tiled around
the door frames instead of cutting them off and tiling under them. I have
been meaning to look for the very same product for this job.