QUESTIONWe want to regrout our kitchen floor that has ceramic tiles. We installed the floor in Feb 2020. we used Mapei unsanded grout from Lowe’s. We heard afterward it’s best to use sanded grout). It was the kind that you ADD WATER to it. Within a week or two the grout started to crumble and crack in many places & got worse in the past month. Huge stressor!Some sections of the floor the grout looks good in that it hasn’t cracked or crumbled but other areas there is a lot of pieces loose or cracked. So we have taken out the visually loose & cracked grout pieces. Some places look in tact and food... So left those alone. However we wanted to regrout the whole floor with sanded Mapei grout of the same color. Would the new sanded grout bond with the previous unsanded grout? My husband said we don’t have to regrout the whole floor just problem areas but I worry that if the currently nice areas are in good shape now that they may crack or crumble overtime like the others have. We recently purchased a premixed grout of Fusion Pro that has a sealant in it. Is that best to use or use the unsanded Mapei grout since the original grout from Feb 2020 is sanded Mapei? Also would it be more beneficial to regrout the entire floor which would cover the problem areas and fill some grooves that don’t have a lot but would cover nice grooves?
ANSWERANSWER - There are many reasons why a grout will crack and come loose. Unsanded grout is recommended for grout joints 1/8" wide down to 1/16" wide. Sanded grout is recommended for grout joints that are 1/8" wide up to 1/2" wide unless you use the special grout for wider grout joints. If the grout joint is 1/8" wide I will always use sanded grout. If the grout joint is less than 1/8" wide then the sanded grout doesn't fit in the joint to full fill it up.
If the grout joints were larger than 1/8" then you might get some shrinkage cracks, but it shouldn't come loose. Often grouts fail because there might be too much deflection in the floor. Or sometimes too much water is used in mixing the grout and/or in cleaning the grout right after it is installed. Too much water weakens the grout causing it to crumble.
To remove all of the grout is a big job and you might chip some tiles during the process, unless if the grout is so weak it can easily be removed.. If there is at least 1/8" depth left in the grout joint it is possible to grout over it with a polymer modified grout and maybe the premixed grout will work too. Before you do anything check with the grout manufacturer to make sure they approve of how you use their product.