What's the best way to clean a really grody concrete floor?

So, as chronicled elsewhere, Himself is starting up a camera shop and he has rented a truly dismal property. (You should have seen it raining indoors yesterday.) I’ve made it my project, once I get the damned sign painted, to do something about at least one of the bathrooms because I just won’t work on the place without a bathroom sanctuary. And believe you me, it is nasty. It smells (not of poop - of old and shut-in and possibly of malice.) There is as of yet no water. We think it’s turned on but we can’t find the valve to, you know, make water come out of taps. A good coat of paint and some scrubbing powder will do for the walls and the fixtures pretty well, IMHO. But there’s the floor.

The floor is, I guess, the first problem. It’s concrete and it’s gross. Will a brush and some soap deal with it? Should it be… sanded? I don’t know? Maybe we could dye it - but it would have to be clean first, right? Are there chemicals you can use? Anybody have any experience at renovating something on the level of, say, a gas station bathroom?

Various concrete cleaners exist. Some consist of a powder which is mixed with water and scrubbed into the stains. Unfortunately, concrete is porous, so extraction to ‘nice and new clean’ is a daunting proposal. Options include: rotary scarification, shot blasting, or hammer scabbling to create a rough surface onto which a self-leveling topcoat can be floated, concrete dyes, epoxy coatings, floating floors (engineered and hardwood), ceramic tile, and VCT/sheet goods.

In all cases, if this is slab on grade, a patch or chloride test should be done to determine what you can or can’t (or shouldn’t) do.

All of that sounds very… expensive. Very expensive.

Would muriatic acid work? It is available at pool supply stores.

Lot to think about.

I would go for a concrete cleaner and then stain it with concrete stain. I stained our new addition and we love it.

It was new concrete. But cleaners are available.

If it doesn’t work, you can always tile over it.

Get to a paint store (not a big box) and ask them.

I would also say that if the roof leaks, and there is no water in the bathroom, the condition of the bathroom floor is the least of the problem.

Good luck. It can be done.

A pressure washer with alkaline cleaner works on some stains, if you can contend with the water generated.
If the bathroom is small perhaps tile or sheet floor is in order.Hide the problem and get an easy clean surface to boot.Heh.

HG is a series of cleaning products with a very good reputation, and they are available on line and in bigger DIY stores and drugstores.

I used to work in a small paint and DIY store, and the first thing we recommended for any concrete was CLR Grease Magnet:


This stuff works great on oil and grease, which is usually the culprit when stains appear on concrete. It’s pretty cheap (maybe $5-10), so it’s probably worth a shot even if it doesn’t work completely. Many people tried Muriatic Acid too, with mixed results. If it’s a small room (as I imagine a bathroom would be), I wouldn’t use the acid just due to safety/ventilation issues.

The thing is, usually people who complain about stained concrete have it on their driveway or in the garage, where grease is common. If the stain was caused by something else, such as paint or solvents, there may be no way to clean it.

danceswithcats is right about your other options. But, one more exists - painting. If your rental contract allows, you can clean the floor up as well as possible (definitely use the grease magnet or similar as paint will not stick to greasy stains), make sure it’s really dry (wait a few days after washing, with doors and windows open as much as possible), and then paint it with a paint called ‘porch and floor’ or something similar. Alkyd paint will wear longer, but latex is easier to apply and has fewer fumes.

I painted a disgusting bathroom floor in the basement of a house I used to rent, and was pleasantly surprised with the results. It was quick and easy, looked pretty good, and felt more sanitary to me. The high traffic areas (ie, a path from the door to the can!) started showing a little wear after about a year, and we were moving out then, but another coat would have been easy enough to apply.

A little harder to find in the States but HG is the ONLY manufacturer we use in my stone company. Their products; cleaners, sealers, enhancers, and the like are the best we have found and we do extensive testing on all the new ones that different reps bring us.

We just picked up one of these yesterday. It doesn’t say so on the site, but the back of the box has these bullet point items on it: [ul][li]Pumice[/li][li]Ceramic Tile[/li][li]Iron[/li][li]Concrete[/ul] Then further says, "Unexcelled for removing. . . Unwanted paint on tile, masonry and concrete surfaces. [/li]
So maybe one of those and a little “elbow grease” will do the trick without any harsh chemicals. Good luck!

Okay, I went over there today and tried just using ammonia and detergent in water with a brush, to see what happened.

I have a new appreciation for dirt. I had, I realized, never actually met dirt before. Now dirt and I are old friends - war buddies, as it were. I had no idea something could BE that filthy.

I worked three hours on one bathroom and made no impression.

What is is, is, I don’t know. There’s something, or several somethings, on the floor. My thought is perhaps that it’s some sort of floor covering that was taken up but never quite entirely removed, with glue or something? There’s some black substance in the hardest-to-get-to corner, behind a pipe, that’s like half an inch thick. The top of it came off like some sort of friable dirt in my gloved hand, but as it goes down it gets tougher. On top it was essentially exactly like soil - like leaf mold or something. In other areas it’s some sort of slimy gray stuff that I think may be old mastic or something? (Hopefully not the asbestos kind that’s in other parts of the building?)

Anyway, it’s, you know, stuff. It’s like eternal dirt - I keep getting rid of it and there’s more under. It’s turtles all the way down.

Are we going to have to get in there with buckets of water and putty knives? Or is there a better way? There is no drain, so I don’t know if pressure washing is possible - there’s nowhere for the water to go except in, like, a shop vac. Which we did use. I’m just frustrated and out of ideas - essentially I worked for hours and just moved the dirt around. I also washed down the walls with TSP and had some of the paint just start sloughing off, and I cleaned the toilet and the sink only it doesn’t look any different.

On a brighter note, the people who own the restaurant next door saw us working and brought us beer. It’s the only nice thing that happened to me today.

Sounds like a project where I’d pull out the commode to open up a drain hole, tape up some plastic sheeting on the walls and go after it with a pressure washer.

Is the concrete itself smooth or rough?

It sounds like you might be looking at tile adhesive or something like that. If there are big lumps of it you could use a floor scraper, like these ones (you can get one at any hardware store):


That would work better on a smooth floor, and be a lot easier than a putty knife.

This sounds like it sucks. Can you maybe post some pictures?

Sounds like you’ve got some mess on your hands. One step at a time:

Get your hands on a good pressure washer, if possible. After pressure washing, allow to dry.

Still got sticky crap on the floor? Get some adhesive remover, like Jasco Adhesive Remover - it’s available in many places, including the big box stores, or they should have something similar. Follow the directions, but if I’m remembering correctly, you let it set and then scrape away at it with a putty-type knife or something similar. With a little luck, the pressure washing should have made this easier so it doesn’t seem like such a huge, daunting task.

Still greasy crap left over, even though the adhesive is gone? Use a concrete cleaner, like Seal Krete OSR.

Etch it with something like Seal Krete Clean N Etch - avoid the muriatic acid at all costs. Unless you are a professional or are hiring a professional for it, just stay away from that stuff. It’s acid. Seriously nasty stuff. The Clean N Etch will give your concrete a profile and prep it for staining.

Hopefully the floor is looking less skanky at this point. From here, you should be able to get any manner of concrete stain. Obviously, the line I’m familiar with is the Seal Krete, but there are plenty of others. The Seal Krete has the bonus of having a water-base, semi-transparent stain, but you may not want to see the old concrete. There are pros and cons to the stain you choose, be it oil base or water base. Oil bases tend to be slippery when wet, and may need a gritty additive (Tred Tek or Clear Grip or along those lines), and water base, while they have lower sheens, may not have as much durability over time (Cabot and Sunproof (PPG) both have a nice latex solid colour stain, usually used for decks, but you can use it inside). These are, of course, simply the products I am familiar with, do some research and see what’s available to you.

It is a bit of work, but you can make it happen. Good luck!

An expensive option: talk to a contractor who does industrial coatings and have the thing bead-blasted and use Mega Seal (PPG) on top of it, holy cow, that stuff looks awesome. I know, I know, probably a little over the top for your project, but boy, does it ever look sweet.

You can do that? It wouldn’t get clogged once the toilet is out of the way? That’s within our ability level?

Because if so, you’ve just opened up whole new holes in the floor for me.

Now, the walls ARE particularly fragile - they’re covered with huge holes where screws tore out, and then anchors, and then sometimes pieces of dowling they tried screwing into. So I’m a little concerned about the building just up and falling down.

About how much should it cost to rent a pressure washer? Is it something we can operate ourselves pretty easily? Do they come in different sizes or something?

Wait. Isn’t the drain pipe above floor level?

You can pull the throne to access the drain,but be aware there will no longer be a trap to prevent sewer gas.Rags/plastic work for temporary stoppers but keep them out of the line.

Forgot to tell you, HOT water with the pressure washer,with a syphon for cleaner.P.W.'s don't really put out lots of gallons per minute, a relative statement to be sure,but less than the supplying tap. So less water than you think to deal with.

     Rental yards probably have a few sizes, and maybe hot water options.Electrics are handy but usually less horsepower than I.C. engines which means less developed pressure.

Yes,the floor flange could be above floor level.

Could we just use a shop vac to get rid of the water?

And when you say hot water, does the pressure washer heat it, or do you need to hook it up to the hot water? Believe it or not the store has been sitting there since the 50’s with no water heater. We’re installing one this week, I think.

Man, forget the hearts and flowers - I do hope Himself understands that scraping unidentified sludge off a bathroom floor for hours is love.

Maybe. Most drains are located below grade, which in a slab on grade construction means they are buried in the concrete and earth beneath. You can have plumbing fixtures below the drain line, but that involves waste grinders and a lift pump to move waste up to the drain.

So-if you want to remove the toilet to give yourself more room, you first make sure the shutoff actually functions on the supply line, and if it does, disconnect the supply. Then, for a close coupled toilet, flush to empty the tank, sponge out the trap water, unbolt it from the floor, and move out of your way. If it’s not close coupled, you’ll need to loosen the ell at the tank, unbolt the the tank from the wall, and then remove the bowl separately. When reinstalling, fit a new wax seal onto the horn of the bowl after removing what’s left of the old.

Something else we haven’t mentioned is that older commercial buildings often used VAT or vinyl asbestos tile as a floor covering. The black mastic which was used to install those tiles is a bugger to remove (I had to deal with it at my previous dwelling before putting in new flooring). Employ appropriate personal protective equipment if that’s the case.

There was an asbestos report that did find asbestos tile in another part of the building, and in the window glazing and duct tape. They took samples of pretty much everything and did not mention bathroom tile in the report (the other bathroom has a lot more of the tile still there, which would surely not have escaped the notice of the inspector - I can see how you might miss that what’s in the bathroom is tile, but the other bathroom has bright turqoise bits right in the middle of the floor.)