Hi Lisa,
Three suggestions:
* A drier dough. In general, wet doughs produce bigger holes. For a
finer crumb you probably want 60-65% hydration.
* Bake to a lower internal temperature, say 190F instead of 205F for
a rustic, crusty bread
* Knead more. The crumbly quality may indicate that the gluten isn't
developed enough. A stand mixer can *really* help with this. But even
without one, try mixing all the ingrients together...let stand for 20
minutes...THEN do your thorough kneading.
The 20 minute rest time is similar to the "autolyze" process...it
lets the proteins hook up together all by themselves without
kneading. Then part of the work is done for you and you don't have to
do as much kneading.
*****
I'd also suggest that for a familiar "sandwich loaf" taste you might
want to substitute milk for some of the water or add non-fat dry milk
to the mix.
Finally, the group might be better able to help you if you post the
actual ingredient list and procedure.
I hope this is of some use.
Best,
Allen
Home baker
San Francisco