Many times, while completing a tile job, a customer may innocently ask the tile installer to freshen up the grout on the bathtub walls or touch up the kitchen floor grout that has seen a lot of traffic. On the surface, this request sounds reasonable, but without the appropriate preparation work, it may not be a wise choice.

Sure, someone looking for a fast fix and quick money can smear new grout over the old grout, but it will not be long lasting. However, the basic question remains. Can new grout be applied over existing grout? The answer is no, at least not for cement grouts. Portland cement grouts, both sanded and unsanded, will not bond to existing portland cement grout.

Given this fact, there are other factors that complicate this process. Bathtub walls and stall showers will accumulate shampoo, crème rinse, soap and body oil on their surfaces. Kitchen floor installations can suffer a similar fate of contamination with airborne kitchen oils and grease along with oil-based cleaning products. If these contaminants are not removed with the appropriate cleaner, they function as a bond breaker to the new grout, which will begin flaking off quickly.

This is the result of smearing a thin layer of cement grout over a contaminated grout joint which fails every time. Photo: Dave Gobis.

The only way to regrout using a portland cement product is to carefully remove the existing grout. This can be accomplished by using a hand or powered grout saw or an oscillating tool with a grout removal blade. This process can be problematic in that the possibility of chipping tile edges is remarkably high and yields unhappy consequences. Additionally, the chances of finding replacement tiles are slim. When this happens, the customer will be unhappy and ask for the replacement of the entire installation.

Since neither the American National Standards Institute (ANSI) documents nor the Tile Council of North America (TCNA) Handbook speak specifically to the issue of regrouting, the best source of information would be the grout manufacturers.

If the appearance of the grout joints is acceptable except for discoloration, the application of a grout colorant on the joints may solve the problem. The existing joints must be thoroughly cleaned according to the manufacturer’s instructions and allowed to dry prior to applying a grout colorant. An additional benefit of this product is that it also allows the joint color to be changed if the decorating theme has changed or the original color just did not work.

When an installer understands that smearing grout over a problem is only a quick fix, he or she will realize that a low cost touch up could yield an expensive replacement. Was it worth it? Think about it before accepting this challenge.