If you’re taking up old tile, you’ll likely find a mess of dense, uneven glue or concrete underneath. This is thinset. Here, thinset is a very fine concrete mixed with sand and most commonly used to set tile. You’ll have to take it up if you want a smooth concrete floor again.
Unfortunately, thinset is always difficult to remove from concrete. You’ll normally have to manually scrape, hammer, or buff thinset off the concrete. You can aid that by soaking the thinset in vinegar or dishsoap, but it will always be a lot of manual work.
How to Remove Thinset from Concrete
Removing thinset from a concrete subfloor or floor is almost always a three step process. This includes wetting the thinset to soften it, manually scraping it up, and then cleaning up the residue. Here, there are several options you can choose in terms of tools and methods. In most cases, those options should depend on the side of your floor and your budget. For example, if you only have a small section of floor, a putty knife or a hammer drill are likely fine. On the other hand, if you’re cleaning thinset from a large floor, you’ll probably want to rent a larger tool.
- Putty knife / heavy duty scraper / Large chisel + Hammer
- Hammer drill
- Angle grinder with stiff wire brush
- Rotary sander
- Floor maintainer with wire brush or Diamabrush
- Chipping hammer
You’ll also need:
- Dust masks
- Rubber boots (if using boiling water on the thinset)
- Vacuum, preferably a wet/dry vacuum
- Safety goggles
1. Wetting thinset to remove it
Thinset mortar is a very fine motor designed to adhere to tile and cement. It contains a large amount of sand, which absorbs water. When sand absorbs water, it swells, sometimes to as much as twice its’ original size. This means that soaking your thinset before removing it can soften it. Here, you should attempt to use water that is as hot as possible. Most professionals recommend using boiling water to increase the speed of absorption.
Soaking thinset won’t make it completely soft. However, it will make it easier to remove. Here, you should normally wait 10-30 minutes after soaking the floor to start taking it up.
2. Using dish soap or vinegar to remove thinset
While there’s no chemical to remove thinset from concrete, you can use light acids to slightly soften the thinset. Here, most professionals recommend using dish soap in your hot water. Dish soap will help to dissolve the bonding agent in the thinset to get it to release the concrete. Here, you can also use vinegar for the same purpose. However, as most thinset bonding agents are mortar and not mastic, neither vinegar nor dish soap will completely dissolve the thinset.
Here, it’s important to note that there are stronger chemicals you can use. However, they are not safe to use on concrete. For example, muriatic acid is commonly used to clean thinset off of tiles. Unfortunately, this acid will also disolve your concrete. If you use muriatic acid to remove thinset from concrete, you’ll have pocks or hollows in your concrete floor.
3. Scraping up thinset
After you give your thinset time to soak and soften, you can go ahead and start scraping it up. Here, you’ll want to start with an opening or a loose piece. Insert a tool under the thinset and start scraping it up. Here, a simple putty knife and a hammer will get you a long way. For the best results, slide the putty hammer under and opening and gently tap the end with a hammer while holding it firmly.
- Putty removal tool or Chisel – Slide the end under an edge on the thinset and gently tap the end with a hammer. Move your chisel and keep finding new edges as you scrape thinset up. You will want to occasionally sweep, vacuum, or clean your space so you can see edges.
- Hammer Drill or Chipping Hammer – Place the tool under an edge and turn the machine on. Hold it steady and keep it at an angle so that it doesn’t damage the floor.
- Sander or Angle Grinder – Buff the thinset off the floor, starting with the heaviest patches. Here, it’s normally recommended to use an angle grinder with a stiff brush, as a sander will take considerable time.
- Floor Maintainer – These can be rented from most hardware stores for around $100 per day. Use a heavy wire brush such as a diamabrush. You’ll want to brace with the machine handle at about stomach level, as it will create quite a bit of torque against the floor.
It’s important to wear protective goggles and a dust mask while doing this work. This is true even if you’ve fully soaked the floor. You’ll always get some dust. Concrete and mortar dust of any kind is hazardous and it is crucial to ensure you’re taking protective measures.
4. Cleaning the mess
Use a shop vac or a heavy-duty vacuum cleaner to occasionally clean up the dust and mess. You’ll also want to do this when you think the floor is near to finished. Depending on how thick the thinset was on your floor, you might be able to sweep up the larger part of it and move it into bags for safe disposal first.
5. Touching up
Once you’ve removed the bulk of the thinset from your concrete, you can go over the floor with a sander or a wire brush to remove any small pieces. Chances are, you don’t need the floor to be perfect. Instead, you just want it to be smooth enough to add new tile or flooring on top.
2 Thinset Removal Methods To Consider
Here are two additional methods that you may want to consider using:
1. Removing By Hand
You can always remove thinset from concrete with a simple putty knife or scraper and a hammer. This can be extremely time-consuming if you have a large floor. However, you can speed up the work by soaking the thinset in water, using dish soap or vinegar, and using a hammer to tap the putty knife. You’ll also want to occasionally change your putty knife or re-sharpen it so you can work the knife under edges.
2. Using an Angle Grinder
An angle grinder is a good way to remove thinset from concrete. However, you’ll normally want to exchange the grinder blade for a stiff wire brush. The stiffer the brush the better. Then, put on goggles and a dust mask. You’ll want to soak the thinset to reduce dust.
Finally, it’s important to ensure you have a firm grip on the angle grinder. Choosing a grinder with a raised grip can be helpful. That’s important because the grinder will create a significant amount of torque against the floor. This means the grinder can kick up and put upwards force on your hands, which could cause it to spin out of control if you aren’t careful.
Otherwise, all you have to do is take the wire brush to the floor and buff until that section is clean.
Softening Thinset For Removal (Prep)
Thinset is a soft mortar made with sand and cement. Normally, you can soften it by taking a two-part approach of swelling the sand content with water and by attempting to break down the bonding agents. Here, the most common method is to use a combination of boiling water and dish soap or vinegar.
In some cases, you might also want to use muriatic acid at a very low concentration. However, in any concentration low enough to not damage your floor, the muriatic acid will do little more than vinegar.
- Use boiling water for the best effect
- Thoroughly wet the floor and let it soak for 10-30 minutes before removing it
- Use muriatic acid to dissolve thinset off of brick walls against your concrete
- If you have thick patches of glue on or in your thinset, apply acetone. You should be able to let this soak for a few minutes and then try to wipe it up
Otherwise, the only way to really soften thinset is to soak it and wait.
Removing thinset from a concrete floor is a time-consuming and labor-intensive task. The easiest way to remove it is to rent an industrial floor maintainer with a concrete preparation brush. Otherwise, you’ll spend a significant amount of time removing the thinset.
Will muriatic acid remove thinset from concrete?
It’s not safe to use muriatic acid to remove thinset from concrete because it could dissolve your concrete. However, it is safe to use muriatic acid to dissolve thinset off of tile and brick. It is safe to use muriatic acid if you dilute it to about 1/24th strength. However, at this strength, vinegar is almost equally effective.
What is the easiest way to remove thinset from concrete?
The easiest way to remove thinset from concrete is to rent a floor maintainer and a concrete preparation brush. Otherwise, you’ll probably want to use an angle grinder with a brush or a flooring removal machine such as a carpet remover. In either case, you should always wet and soak your thinset first.
How do you remove stubborn thinset from concrete?
Try soaking your thinset in a weak acid such as white vinegar. You can also use a diluted solution of about 1 part vinegar to 7 parts water. Thoroughly wet the thinset and allow it to soak in. Then, use your scraping or hammering tool to remove the thinset.
How do you remove hardened thinset?
Normally, you can wet the thinset and then scrape it up. This is not easy. However, it does work.
Does vinegar remove thinset from concrete?
No. However, the light acid content of vinegar will work to slightly soften the thinset, making it easier to take up. Soaking your thinset in vinegar or a vinegar and water solution can make it easier to scrape or hammer up with another tool. However, it will not remove the thinset for you.
Removing thinset from a concrete floor is not an easy job. However, there are several tools you can choose to make the job easier. If you have a larger space, consider renting a hammer chipper or a floor maintainer. Otherwise, doing the work by hand is probably the best call.
Good luck cleaning your floor.