Once the area is clean, you can start filling in the gaps. There are a few different materials to fill in gaps in your grout, but we recommend using a premixed grout. Using a premixed grout is the easiest way to fill grout gaps, as mixes come in a wide variety of colors.
You can always regrout to fill in voids. The trick for doing this with water-based grouts (not epoxy-based grouts) is to mist the mosaic with water several times and let it soak in so that the existing grout is damp and so does not suck the moisture out of the new grout before it can harden.
But yes, you can wet it (lightly) and go over it again with more grout, even if it is unsanded. Once you get it filled properly and it's allowed to cure the unsanded will work fine, it's just a LOT more work to fill, let it cure (shrink), fill again, etc. Once filled and cured the stability is the same as sanded grout.
Sponge: A damp sponge can be used to push grout into the joints. While it may not be as effective as a float, it can still get the job done. Use the edge of the sponge to fill the gaps.
ANSWER - It is possible to grout over existing grout if there is enough depth to do so. 1/8 inch depth may or may not be adequate depending on the type of grout used. A latex modified grout may work, but you have to properly clean the existing grout to ensure the new grout adequately bonds.
You can apply new grout right over the top of the old grout. To do this, all you need is a grout removal tool. Use the tool to strike out the old grout, making sure the depth is at least 2mm, which is about the thickness of two dimes stacked one on top of the other.
Mix up some more grout, and use your finger to fill in the holes really well. Allow to set then wipe with a sponge. In the future, when doing grout, make sure you're applying it correctly by working it into the line at a 45 degree angle, then again using your float, press the line perpendicularly.
Spot repairing grout is not only possible, it's also a great way to fix cracked or crumbling grout lines.
If the grout is runny and can be poured like a milkshake, too much water has been added. You can fix the problem by adding more powdered grout and blending the mixture until the grout thickens.
Fortunately, the holes in the shower's grout can be repaired. If the grout is in poor condition, you may need to replace it completely, but if the grout is in overall good condition, fixing the holes might be sufficient. One thing is certain: the holes in your shower grout should not be left unattended.
Tiny pinholes develop over a period of time. This process is normal, as after some time, the foundation of the house sinks a teeny-weeny bit deeper into the soil, thereby shifting the structure of the house. Grout is a very delicate material as it is made from sand and cement.
For cementitious grout, joints smaller than 1/8″ generally should only be grouted with unsanded grout, and joints of 1/8″ and larger should only be grouted with sanded grout. Joints larger that 3/8″ usually need a more heavily sanded grout to accommodate the large joint.
Using caulk instead of grout in areas where grout is traditionally employed is not advisable. This is because caulk lacks the structural stability and durability of grout.
Mix the grout powder (you can buy it at the home improvement store) with water. Use your fingers to apply the grout between all tiles. (You can also use a rubber grout floater). Remove excess grout.
Grout pens are designed to cover old grout and fill in gaps between tiles, meaning they are an easy and effective way of refreshing bathroom or kitchen tiles.
Using a premixed grout is the easiest way to fill grout gaps, as mixes come in a wide variety of colors. Additionally, these mixes have added sealants to protect against dirt, water, and mildew infiltration, which will further reduce issues with gaps long term.
You would also notice that adding new grout will not be aesthetically pleasing, as the new layer would be thin. This means that your old grout will be seen beneath, and if you were to only treat one area, you would see the difference in the “repaired” area versus the area that you did not add grout to.
Grout, which is the mixture of cement, sand, and water used to fill the gaps between tiles, is porous and can easily trap moisture. Grout is porous and readily absorbs water, making it an excellent breeding ground for mold.
Fixing missing grout is pretty similar to repairing holes. Give the area a good clean, put new grout in the spots where it's missing, and smooth it out with your grout float. Clean off any extra and let it dry completely.
Generally, you should be okay to mix up some grout and touch up any trouble spots in your new grout. Stuff like pin holes, scratches or low spots can be touched up with fresh grout the next day. The trick is to blend in the new grout with the old so make sure you mix it the same way that you mixed it the day before.