Home Repair and Paint Guide

It takes a certain level of skill to grout tile. Grout can be ruined if mixed with too much water, and will be extremely difficult to apply and smooth if too thick. If you are not familiar with grout application, practice on a set of old tiles before starting your project.

All powdered wall and floor grouts are made from Portland cement. Some grouts have additives such as powdered latex or acrylic to improve bonding. Portland cement can absorb water vapor from the air if left exposed. That’s why grout bags are lined with plastic. Don’t open a bag of grout until you are ready to use it. 

The correct consistency of grout will stick to a putty knife and not droop or fall off. As stated earlier, mixing grout with too much water will cause it to fail over time. If you open a bag and find lumps or clumping, don’t use it because water vapor has already been introduced. You cannot discard the lumps and continue with the rest of the powder. Throw the entire bag away and start with a new one. The grout should look like a bag of baking powder, with no lumps.

Mix enough grout for about 30 minutes of work. This will keep it from hardening and also keep you from trying to move too fast. Make sure you have an extra bag in case you mix a batch with too much water. If this happens, just add a little extra powder. If the grout starts to harden in the bucket, discard it and make a smaller batch. Don’t try to “save” it by adding water. This will guarantee premature failure at a later date.

During application, use a sponge that is only damp with water. Squeeze all excess liquid from the sponge before working the grout. Don’t leave water sitting on the surface because this will weaken the material the same way as mixing it too thin.

If you live in a very low humidity area, run a humidifier for 48 hours after the grout has been applied. The water vapor keeps the grout from drying too fast, which would weaken it. It takes several days for grout to reach full strength and the first few days are critical.

Once the grout has cured completely, you should use a grout sealer. This will lock the grout down and protect it from penetrating stains. It also makes tile cleanup much easier because spilled liquids will not stick to the sealer. Use a high quality brand and follow the application instructions.