Good afternoon 92592ds,
Thank you for your question and welcome to the community!
We've seen this kind of issue come up a lot here, with lots of posts talking about removing adhesive from a concrete subfloor.
I've worked at my stores paint, tool rental, and flooring department here in Atlanta, and I've seen this question come up frequently in each one.
The absolute best way to remove adhesive over a large square footage area such as yours is to first use a tool that will physically remove as much glue off as possible. The tool for the job? Using a floor maintainer aka polisher. These can be rented out at your local Home Depot that has a Tool Rental Center.
Since you have a concrete subfloor, using the floor maintainer above alongside a black rough scrub pad will get rid of a majority of the adhesive. You'll most likely be going through at least 4-6 pads for a room this size. The great thing about renting is that you can rent out as many pads as you need, and return the ones you don't; so stock up.
As I stated before, this will get rid of most of the adhesive but not everything. In those hard-to-reach and just stubborn spots of adhesive, you'll need a strong adhesive remover to cut through the glue. While you can use the following product on all the floors, it will take up too much time and money to do this versus using the floor maintainer above. Reason why is not just the up-front cost, but in the labor. You'll need to apply the adhesive remover in a small workable section at a time, being careful to scrape up the area afterwards with a chemical-resistant scraper and wearing stripping gloves.
As for the adhesive remover, I recommend one that is in semi-paste form and not liquid. This type is better and works great for cutting through any type of floor adhesive. It won't give off as many fumes as the liquid type, but it still should be applied with good ventilation in the room and wearing the gloves shown above and goggles.
You can apply this with a cheap, chip brush and let set for 20-30 minutes. Make sure you dispose of any rags or glue/solvent accordingly. It also helps to invest in a good set of knee pads for this step as well.
Depending on what new floor you'd like to install on top of the concrete will determine if you need to take all of the adhesive up. Fortunately, for most tile and wood installations, as long as you get the subfloor as clean and level as possible, you should be okay. That's not to say the concrete still may have some adhesive, but as long as it is down to the level of the concrete (about 1/8" or less) you can put your new floors on top of it.
Any further questions, please do not hesitate to ask and we'll be here for any future projects you may have.
aboveaveragejoe
