I need to paint hallway and it had been painted with oil. I now wish to use latex semi-gloss. Is this OK?
OK? Yes, but conditionally. You may as well convert to latex at this time. Here's how.
You will need to sand the sheen of the existing finish. Now don't get all shaky. It's really not that hard to do. You are trying to dull the sheen, not sand off the paint. Next you will need to prime with a bonding primer. Ask your local paint dealer which is best. One coat of primer applied according to label directions should be sufficient. Last, apply two coats of latex finish in what ever sheen you prefer.