sanding the floor

I went to Home Depot and talked to the guy in tool rental about a drum sander for prepping the floor. According to him, the sandpaper will get torn up using it on concrete and that basicly, it was a very bad way to do the job. of course the machine he reccomended was $200/day vs. $65/day for the sander plus sandpaper @ $7/drum. Obviously I could buy a whole lot of paper before I hit the break even point. I told him that I just wanted to prep for epoxy, so just to rough up the surface a bit and clean up a few spots.

Has anyone used a drum sander on their garage floor?

Were you pleased with the results?

What grit paper should I be using? I'm just guessing 150 or there about.

How long did it take you?

Would you do it again?

My garage is 21 x 29, so just over 600^2 ft. It was built in 1985 and i have no idea if it has a sealer on it or not. The other factor is that the drum sander will fit in the trunk of my car. The shot blaster that I saw would not. Thats a big selling point for me because otherwise I have to beg/borrow/steal a truck. I'm either doing a 2 part epoxy or maybe the new POR-15 product.

A drum sander will work, just remember to keep it moving, otherwise it will sand too much of the coating away. You want to "scuff" it up, not remove it. I typically use a 60-80 grit sandpaper (on a rotary buffer) when scuffing epoxy, this will break the surface and leave a "profile" in the coating for your new epoxy paint to stick to. Tack rag the sanding debris before you apply the new finish. Get a palm sander or something you can get into corners with, or make sure to hand sand thoroughly any spots the machine caqn not get to. It can take the better part of a day, mabey 6-8 hours depending on your proficiency with the sander. If the coating on the floor is not failing and you have confience it will not, sanding epoxy and applying a "re-fresher" coat is easier than a complete removal and a new application.

I used a drum sander between coats of epoxy. I think I used between 30 and 60 grit. It took me about 3 hours for my 22'x24' garage. I'm satisfied with the results

Just to be clear, I'm going to be finishing a floor which I believe has never been finished, not roughing up an existing coating.

It sounds like it will work either way though.

Stay away from Home Depot and go to a real tool rental comany and ask about a concrete floor grinder. I rented a EDCO grinder for $100 for the day. I used it about 6 hours but anything after 4 was considered a full day so I didn't have to take it back until the next day. The grinder will take your floor down to where it feels about like 120 grit sandpaper. Thats what I used before I applied my colored sealer.

The EDCO grinder works well, and upgrade to the diamond blades if you can. I was under the impression you were preparing an existing epoxy coating for a new product. The grinding will create a textured surface, increase the surface area of the floor and typically cause the use of more products. It is not a necessary step in some epoxy systems, it depends on which product you are using. It will create a good profile for epoxies to bond to.

Ok I think I'm going to definitely grind or shot blast the floor. We closed on the house today and I got a real good look at it with nothing on it. there are a lot of unknown stains on it. most aren't in the typical spots where cars leak so I'm really not certain what most of them are. one big crack to grind out and fill, but thats manageable.

I was hoping to get all of this done before I moved in, but the timetable is too short to get it completed.