Accidentally Used Mortar Instead Of Grout (What To Do?)

One of the common mistakes that occur during tile installation is accidentally using mortar instead of grout. It’s very easy for one to confuse a bag of grout for mortar, especially if you are not an experienced tiler.

If you have found yourself in such a situation, there is no need to lose your mind. Below, I will take you through the steps on how to remedy this situation and also share useful information about both mortar and grout.

Tiling the Wall

Is Mortar a Suitable Substitute for Grout?

The first thing we have to address is whether mortar can be used as a grout alternative because this will dictate what you should do next.

Mortar isn’t a grout substitute. The only use of mortar during tile installation is to promote adhesion between the tile and the substrate. On the other hand, grout is used as a filler between tile spaces.

Many people assume that mortar and grout have a similar composition. But that’s false. Mortar is thicker than grout. Therefore, when used as a filler, you will notice that it won’t flow easily.

Also, this property can make mortar leave holes or gaps between tile spaces as it dries. This will allow water to seep through the tiles and it can also affect the aesthetics.

mortar bed

What Should You Do When You Accidentally Use Mortar Instead of Grout?

From the above, it’s clear that mortar shouldn’t both knowingly and unknowingly be used as a grout alternative. But if it has already happened, here are some options you can explore.

1. Remove the Mortar and Re-Grout

If you have accidentally used mortar instead of grout and you have discovered your mistake within minutes, this is the best remedy to your situation.

Before the mortar starts to dry, grab some sponges, wire brushes, or screwdrivers, and start removing the mortar. Wet mortar is easier to remove than dried mortar especially if you use water.

You don’t have to remove every piece of mortar in between your tile spaces. Only remove an adequate amount of mortar to make enough room for grout filler.

The spaces between your tiles need to be big enough for grout to grab onto. Once the mortar is removed, prepare your grout, install it and you will have corrected your mistake.

2. Seal the Mortar and Let It Stay as It Is

Removing mortar isn’t an easy job, especially if it has already dried. It’s messy, tiresome, and time-consuming. This is why some people prefer to let the mortar stay between tile spaces as a filler. However, to prolong its lifespan, they cover it with a sealer.

You should only use a sealer if the mortar was properly installed between the tile spaces. If there are holes left behind, the sealer will be ineffective, and eventually, the mortar will crack and get damaged.

Also, this remedy applies to scenarios where you are comfortable with the mortar color in between tile spaces. If you don’t like the color, you will have no option but to remove it.

I don’t recommend this latter option because there is no certainty that the mortar will do a better job than grout. Use it as your final option.

Grouting tiles seams with a rubber trowel

What’s the Difference Between Mortar and Grout?

Now that you know what to do when you accidentally use mortar instead of grout, I think it’s fair that we compare these two masonry materials, in detail. The more you know about mortar and grout, the less likely you will make such a mistake in the future.

Grout is used to fill spaces between tiles. Apart from enhancing the beauty of recently installed tiles, grout holds the tile in position. it also prevents the entry of water and debris between tile spaces.

Grout also makes tiles comfortable to walk over. Grout is mostly made using Portland cement and polymers. Color pigments are added to determine the design. Grout is also available in pre-mixed or dry options.

Mortar, on the other hand, is a tile adhesive. It’s a bonding agent that holds together tile and substrates such as cement boards. Mortar is used below the tile and not in the spaces between.

It is made using lime, Portland cement, and Coarse sand. There are different types of mortars such as thinset, type S, N, O, M, and K. Each formula has its specific use. I won’t get into much detail about this because that’s not the focus of today’s article.

Even though both mortar and grout contain Portland cement, they are two different products that shouldn’t be used interchangeably.

Tile manufacturers are always clear about the type of mortar and grout their tiles should be used with. If you go against these recommendations, there is a huge chance of failure.

Should You Scrape Out Mortar If It’s Accidentally Used Instead of Grout?

As inconvenient as this approach may seem, it’s the best solution. Yes, you can seal mortar if it was accidentally used instead of grout. But you have to remember that mortar and grout shouldn’t be used interchangeably.

If the mortar leaves holes or gaps as it dries, there will still be spaces between your tiles and water will seep through. If you haven’t installed a water barrier below the tile, moisture damage will be inevitable.

If it’s possible, when you accidentally use mortar instead of grout, look for a screwdriver or a wire brush and start scraping it off.

Water can soften up mortar making it easier for you to remove it. If the mortar is super dry, you can use acid-based cleaners to weaken its adhesive strength.

When you scrap out the mortar between tile spaces and replace it with grout, you will enjoy peace of mind knowing that you have used the right product and it’s going to serve you for the longest time possible.

Also, scraping ensures you don’t have to endure a grout color that you don’t like.

How Long Can Mortar Last If It’s Used Instead of Grout?

The funny thing is that some people have accidentally used mortar instead of grout, which has lasted for years.

When you add a sealer, it can help push the lifespan of mortar in between tile spaces. If it was installed correctly and didn’t leave any spaces when it dried, mortar can last for an incredibly long duration.

There are a lot of ‘ifs and buts’ associated with this scenario. This is why I don’t recommend it.

What about the Vice Versa: Can You Use Grout Instead of Mortar?

You also can’t use grout instead of mortar. Grout is not an adhesive. It is a filler. So, when you spread grout below tiles and hope that they will bond to the substrate, you will be in for a rude surprise. The tiles will eventually come out.

The good news with grout is that it can be turned into mortar by adding acrylic glue. This however only works for sanded grout. Other types of grout can’t be converted into mortar.

Even with these adjustments, grout will always be lighter than mortar. This can, therefore, affect the structural integrity of the tiles.

In scenarios where you accidentally use grout instead of mortar, there won’t be room to make the above adjustments. You won’t have any option other than removing the grout and replacing it with mortar.

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