https://imgur.com/a/N47pzSO Photo of the glue, and overall room.

baseboards need to be removed. Don't cut corners

Go to Home Depot and rent a concrete grinder and a good HEPA vacuum. It's basically an angle grinder with a diamond cup wheel and a dust cover with a vac attachment. Grind off all the glue down to sound concrete then use whatever thinset that Schluter recommends for this application. Have fun and wear a good respirator as well.

Going to jump on this and say if you have a window in there, point a fan out that window and close the door behind you and you will get almost no dust in the rest of the house.

Unfortunately no window - interior room. Attached office has a window and nothing in it currently, so I will open that. Thanks!

EDIT: HD locally does not have any of these machines. Most HD's within 100mi show a stock of 0, but there is a single unit at a HD 35mi away. Are these normally hard to rent?

Will be removing them. Already removed the old bull nose trim. Just doing this in phases.

Yes, get the baseboards off. I'd take out the toilet too, you'll regret it later if you don't, and it's not hard to do.

The ONLY mortar for putting down Ditra is regular unmodified thinset, A118.1 Because it has to cure purely from the chemical reaction of the cement as it will be covered by the plastic Ditra. Don't use anything with "crack preventive" or "modified" in the name.

As to your floor, as long as the glue is well and truly stuck to the concrete and doesn't have any large bumps or trowel lines you can lay the thinset and ditra on top of it. Looking at your picture, I'd go at it a bit with a bladed floor scraper, but no need to get too picky. The Ditra is an isolation membrane so it'll separate the concrete from the tile bed.

Depending on the model—sometimes. Those dedicated concrete grinders can be quite large and are used for prepping large surfaces. If this bathroom is smaller you might be able to use an angle grinder with the appropriate (diamond) grinding wheel and lay it broadside onto the surface to get rid of the glue. This isn’t like a cutting blade. It’s built to grind on the face of the disc—not the edge.

There are also a number of handheld electric stripper/grinders that can be paired with various low grit sandpaper discs for this exact purpose. Maybe a wire brush wheel for a drill could work? My experience with those has been they sometimes don’t work well due to the type of glue

Dust collection will be an issue. Some grinders have a shroud to collect dust at the tool or they can be purchased on Amazon. You could have a 2nd person hold the intake pipe where dust comes off. You can buy most of this stuff at Harbor freight rather than renting for short money or even HD for reasonable price and is likely easier than renting.

As others have said, Negative air pressure in the room you’re working in should be used in addition to collecting dust right at the tool with a HEPA vac. The vac will not get everything and silica dust has a tendency to travel and linger and is also no joke health wise.

Does it have an old bath fan that works? It will likely get caked in dust though, but should do the trick. Struggling to think of an alternative if no window available. Maybe you can rent or buy a in line fan with a vent pipe?

My local HD has a few. If you own an angle grinder you can buy diamond cups and the shroud attachment on Amazon for not too much $.

If the regular thinset will bond to the glue (likely white mastic) without fail, I will go this route if I can get the floor scraped up some more w the blade on a pole. Thanks!

Crazy thing is there was no vented bath fan, only a ventless fan. The builder stupidly ran the main HVAC plenum in a way that blocks outside access from this bathroom, but I found an alternate route out and am retrofitting a new fan.

Ventless fan is useless for anything except muffling noises.

This is not true. Schluter all set is a modified thin set which obviously can be used with schluter ditra and kerdi products.

Toilet is going out too. Leaving it until the plug I ordered comes in for both the shutoff valve (really old) and the drain. I have a new Toto Drake to install in it's place once the tile work is done.

Plus... You get the warranty with all set. This is the route I'd go. You can grind the rest of the glue down or use a primer over the top as well. Not that it's totally necessary but it's an option.

Be careful with using a bathroom ventilation fan to vent out dust if you are sanding/grinding the remnants of the glue off. Those fans are really only designed to take humidity at most out of the room. The dust particles from this would be super sticky & gunk up the fan, those things are not generally designed to be easily cleaned besides just the cover, and you could blow the motor out pretty quickly if it gets too gunked up.

He’s not wrong either though. You shouldn’t use “modified” thinset unless it’s All Set

Have you tried a 5" wide heavy duty floor scraper? You can soak the glue in hot water. It's still a workout, but it should come up. I had to remove a vinyl floor from concrete like this in a bathroom.

You can use modified to put tile onto the ditra, but NOT to put the ditra onto the substrate.

No one here has mentioned that there are primers that can go over top of the glue, and that thinset will bind to.

Specs calls for nonmodified mortar if I recall.

You realize you need to level your floor right. Not only do you need to remove the glue. Grind and scratch your concrete. But is very, very, very likely not flat enough for tile. Which means you’ll be pouring an SLC over your freshly ground concrete floor.

Do it right and don’t be a hack.

Also you need to pull your toilet off. Sink cabinet. And baseboards.

Versa Bond works fine with Schluter products.

The glue for the vinyl flooring is a pressure sensitive glue all you need to eliminate the tackiness is some concrete powder form and throw a handful on the floor and sweep it around, then get some 5 minute epoxy adhesive from hd and glue down your schluter strip good to go!

Why not put down 1/4” hardiboard with thinset and screw the shit out of it? Use that as your new surface to put Ditra on top of? Don’t buy the Unmodified stuff from HD, that stuff is as good as sand.

I was looking for my own project and it looked like it would be between $100 and $140 if you already owned an angle grinder which is another $50 to $150 depending on the tool brand. Plus a vacuum, another $40-100.

My neighbor did his whole floor with one during his COVID so it is possible to do a lot of work with one of those.

Mapei makes a product called Eco Prim Grip. You can go over it with that and then use All Set.

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Back in the Early 2000's I bought a built in 1994 house in Florida that was all glued down sheet vinyl on concrete. I wanted to tile it and ripped up this ugly black and white vinyl. But the glue would not come off easily. Now mind you it was over 2000 square feet. Scraping it did nothing and I was at my wit's end. So someone had recommended a grinder also but just before we were heading to rent one I had a 5 gallon bucket full of water that I accidentally knocked over and got a good portion of the glue wet. After a little bit of time my friend took a scraper and low and behold the glue just came up.

Once we figured out it was water based glue we were able to remove the glue with no fuss at all with a big scraper. Saving a big mess with a grinder. You may want to see if the glue is water based by putting some water on it and wait a bit. I still live in the house and the tile is holding up great. Oh, btw why do you want to put ditra on a concrete floor? I don't see a need in that unless maybe your heating it.

Ditra is an uncoupling membrane. Prevents cracks in the concrete transferring to the tile

You can buy vinyl floor glue remover at the hardware store. That may work. If not, I used a propane torch and heated it up then scraped it off.

The ditra install manual states unmodified thin-set mortar A118.1 for concrete substrates

The ditra install manual states unmodified A118.1 for concrete substrates

Considering that it's a bathroom, so presumably not a massive space, you might at least try using a reciprocating saw with a scraper-blade tool to remove the glue.

Shit - my bad. I missed the concrete part.

Get one from harbor freight, it would last enough to do one room.

I only looked because I used ditra a couple years ago and wanted to make sure I didn't fuck up my bathroom lol

Heat gun to loosen old glue. Schluter All-Set, then Ditra.

I did it myself with a small 4.5" grinder and a dust cover attached to a shop vac. No HEPA filter needed when you have a bag in the shop vac.

One downside is that you're always bent over and on your knees so your back and knees might hate you for it.

It takes a long time with a small grinder. Depends on the surface, obviously. I was doing half my basement.

A larger machine from home Depot might do it faster and also might allow you to control it while standing upright.

Also glue might gum up the wheel.

I had some tar-like substance under the paint and it took a long time to eat through that. The wheel would melt it and spread it around. I ended up using a lot of chemical/gel strippers to remove that tar.