Cracking is the most common cause of damaged grout.
Marble floor without grout.
If my hunch is correct regarding the sizing of the tiles then try and have the the grout lines on the base board hit the mid point on the floor tile.
This insures that there is no bleed through effect of the ridges in the thinset you spread on the surface.
Make sure to apply an even coat across the entire back of the tile including the edges.
Repairing cracks with caulk.
Using the flat side of your trowel skim coat the back side of the marble or travertine with a thin layer of thinset.
Removing and then re grouting these lines is a great way to revitalize the look of a marble installation without having to go to the expense and hassle of completely re doing the floor.
How to clean marble tiles without etching the tiles marble floor cleaning tips.
For most granite and marble tile i install i use either 1 32 or 1 16 inch grout lines.
If the grout lines still do not come clean it may be necessary to remove the stained grout and regrout the marble tile grout to restore the grout to its new looking condition.
Laying a marble floor without grout is possible so long as proper care is taken to assure your layout is perfectly square.
You will be butting the tiles up against each other so there isn t any.
The best thing to do is use the smallest grout line your particular tile will allow and get a grout that closely matches the tile.
Many homeowners prefer the appearance of ungrouted tile.
Perfectly cut edges will not perform better than regular tile when friction occurs so they can still cause a variety of problems if you opt for a no grout tile installation.
As you walk on tile floors the grout becomes weaker and can eventually start to show unsightly cracks.
Grout works to prevent moisture and detritus from entering and getting stuck in the grout joints.
It is important to find ingredients that will clean effectively yet be mild enough to cause no damage to either surface.
Therefore in order to get the grout lines to match you may need to cut either the floor or the base board tiles which can add considerable cost to your project in terms of labor and material.
In most other tile i will use 1 16 or 1 8 inch lines.
Epoxy grout works great to resist stains but it may be a bit difficult to apply.
It is a relatively easy project and it can be done quickly allowing you to make a dramatic improvement for a small investment.
Before installing your marble tiles without grout consider the function of grout and whether it is appropriate to eliminate the step.
Even if rectified tiles allow you to avoid using grout without having the result look unaligned the materials are still in danger of being chipped or damaged.