Need opinions on concrete floors.

You'll need to reseal them every 3-5 years. They tend to dull over time. I like the look.

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The stain is very picky (acid stain) and it may not penetrate the old glue. For example I had a new house and duct tape got on the floor for two feet. The stain wouldn't get thru it 100%. I scrubbed the hell out of it too.
I'd practice a spot before doing the whole floor.

We did our bedrooms three years ago. Low maintenance. Prefer wet look which requires occasional polish, simple to do, apply with mop.

The actual staining was more than I expected. Don't know if I would do it again. We also have porcelain tile and wood laminated flooring in our home.

I did them twice and loved them.
The prep work is critical, for sure. Here's my take on the stained/sealed concrete:

Cons:
- takes a long time (prep surface, spray etching stain, neutralizing wash, then a few days to dry before sealing).
- could possibly not take if glue or other stuff penetrated the surface

Pros:
- If you don't like it you can always cover it with wood floors or carpet
- Cheap, look great and last well