Okay, I have a formerly painted concrete floor which needs repainted. Here are the questions?

Do I need to scrape off all of the old paint?

If yes, other removal ideas?

Surface prep?

Prime?

How long should the paint remain?

How would all of these questions differ with painted cinderblock on a vertical surface or non-walking surface?

 

Anything loose, yes
Scraping is best
Power washing isn't a bad idea in some situations
Can depend on the paint
If using some like Moore's Floor & Patio latex enamel, then a super good cleaning with an "orange" -type cleaner
*any oil spots at all and latex won't work*
...or power washing
Not with the paint mentioned above
How long will it last?
Depends on the situation, and how well you prep
I'm on the water and it's usually basements so it doesn't last as long as it would in other situations (the floors can get a lot of pressure from the ground water, lot's of cracked foundations...etc...)
Still, I can get a good few years out of the M's F&P no problem, even if it's a damp basement-much longer if it's in good shape
Different paint
Proper primer then wall paint works for that

 

I'm going to be painting my porch floor soon also. As far as cleaning with a pressure washer, do you recommend shooting soap through it or just pain water or both?

 

If it's in good shape I'll use a little TSP mixture to clean it
PW it off if I can

For concrete needing mild cleaning I have used the cleaner that can go through the PWer (don't use anything not labeled OK for PWers)

For tough stuff I almost alway hand spray cleaner, or simply mop it, scrub it up, and power wash it off (if a PW is appropriate)

The thing is, it's not alway good for me to PW
A lot of my jobs are damp basements that don't dry out real quick
Someone in AZ, maybe a PW is SOP...lol

Also the condition of the concrete could be a factor

I like to when I can, but it's a judgment call as to if it's OK in a basement

If it's a porch with lots of windows and can be opened up-yes I'd PW it, no problem...I'd prefer it, even if I had to wait a few days for it to dry

 

Well, mine's a porch, completely open, only half of it is even roofed. We have some general purpose PW soap, made by Zep I think, its purple.

Most of the paint is in good shape, all of it in the covered part is, but some is peeling so I plan to blow as much off as I can. I also plan to use the BM floor paint.

 

Sounds familiar
I may have used a yellow (?) Zep before
Sounds like a plan

 

I hope so, wife's riding my butt about it