You will more likely have good results with a flat paint, as it is more forgiving in sheen retention.

As a former contractor, I always tell people getting bids, not to accept merely that the contractor intends to use Sherwiln Williams or Ben Moore paints, but to ask for exactly what line he intends to use. Then call the local dealer and ask if this is the "contractor's grade" or if it is the good stuff. All the major brands make contractor's grade and really good paint. Using less than the best paint is being penny wise and pound foolish.

With flat finish, it doesn't matter so much the quality. I use cheap paint on ceilings because it hides the best and dries to the flattest finish possible, not because it's cheap. The more expensive flat paints do have some durability and can be washed somewhat, but really flat paints are what they are and if you are looking for durability you should use a washable paint. If you absolutely hate sheen, then I understand. In your situation, one coat of good flat over crappy flat should be fine.

There are good washable and even scrubbable flat paints. So quality does matter for flat paints. With a username like paintguy I'm surprised you think all flat paints are about the same.

The best recommendation I can give is that I use Behr Ultra Flat throughout my house and have been very satisfied with its washability and scuff resistance.

There are great variances in flat paints. The premium flats will use 100% acrylic resins and only premium titanium dioxide as the white pigment. Cheaper paints use such things as calcium carbonate ( chalk) and clay as cheap filler pigments. Obviously, these degrade washability.

No, you are confused. But this is not your fault. It is the fault of the industry. There is a difference between dead flat and washable flat. If you are interested in using a dead flat paint, one that has no washability, then they are all pretty much the same and sometimes it is better to use a cheaper version. Cheap flat paints are filled with cheap ingredients like chalk and clay, It is these cheap ingredients that make the dried paint film look good in critical light (no flashing, roller lines, etc) and also helps to make the paint easier to touch up. However, because of the cheap ingredients, the paint film has no integrity at all, which means if you touch it or bump into it, there will be a dead spot or a dull spot. This is why we like to use it on ceilings. It looks great and nobody will touch a ceiling.

A washable flat is a different animal entirely. It's not a flat paint at all, but the manufacturers will call it a flat anyway because they are stupid. A washable flat should be treated like an eggshell or a semi gloss or any paint that forms a protective skin on top of the paint film (enamel). The best system for these types of washable paints is a quality primer followed by 2 topcoats. The problem is that it can be hard to tell when you are shopping for paint which paints are dead flats and which paints are washable flats. It's even more confusing when manufacturers of dead flat paints are putting the word 'washable' or 'cleanable' or 'scrubbable' on their cans of dead flat paints!

So, if you come on a forum asking for advice about flat paint, we assume you are talking about dead flat. If you want advice about washable flat paint, then you should have specified.

Very informative. And it clarifies your first post to this thread. In context I see what you were trying to say.

I would much rather have a washable "not dead flat" flat paint than a truly dead flat paint that will will show marks every time you touch it. My top coat will be SW Emerald flat paint. I hope this will be a good spot resistant washable flat. Paint reviews are all over the map, even from professionals. For every person that thinks one paint is terrific there is another who thinks it is bunk.

I went with SW in this case because they have the perfect color I was looking for and Emerald is their top of the line. Hope it lives up to their marketing claims.

I have used Emerald, but not the flat version of it. It is supposed to be comparable to Benjamin Moore Aura, which is really the king of washable flats IMO (actually called Aura Matte). Over the years, of all the washable flats and mattes I have used, none of them seem to be as washable as advertised, but all are certainly more washable than a dead flat. I tell my customers now that if you want true washability, then use an eggshell. If you don't mind some sheen, then use an eggshell. Painters will disagree with me and some also agree, so you are right in that we all have preferences and opinions. Another thing I have noticed from customers is that they want washability, but they never wash their walls. A lot of them may call me for a touch up and say that the walls or their trim got marked up and so I ask them, have you tried cleaning it? Guess what they reply. This may be part of the reason why it's hard to gauge which paint are washable and which are not.

Anyway, in your case, I would request that the painter apply two coats of Emerald over the cheap paint that he used. Often times what happens is that one brand does not look good over another brand when you just do one coat. Two coats may be needed for sheen uniformity (I realize it's flat but there is still a slight sheen since it's a washable flat). Plus, the performance of the paint will be better with two coats of Emerald.

So it just occurred to me that the crown molding also got the crappy flat paint. And I'm going to want something with more sheen on the crown molding.

You guys were saying that good paint with sheen over a crappy flat paint could be an issue. So what do I do now? Cover the crappy flat with a primer and then repaint? If it matters, the color is a bright yellow.

Yes, a good enamel undercoater primer and then a good top coat.