I hardly ever will spec one coat. The only time I may consider it is when I am painting with flat and the color I am going over is very close to the new color. Is there any patching? There almost always is. Any repair work/patching is going to require two coats or it will flash through the finish coat layer. If you try and spot prime those patches, usually those spot primed areas will flash. This is why trying to do one coat is just not worth it. Washable paints require two full coats for the sheen to look right. This is especially true when painting over flat. Two full coats are also required if you are looking for that true washabilty/scrubbabily that the paint claims to have. It really has nothing to do with how good the paint is that you are using. It's about film build. I realize there are plenty of painters out there that spec one coat for most of their jobs. I think it's wrong.

I can't add anything to PG's wise words here....

It's SUCH an "Old-Wive's tale" that 1 coat of paint is sufficient! UNLESS, as PG says, it's just a maintenance coat/similiar color.

Your new paint COATS can be viewed as a "wear layer".
Even if you're the world's-best painter, there's STILL ONLY ONE thin layer of paint...subject to all of a homes' "wear & tear" factor over the years!

Ask a Woman...how many coats of nail-polish are normally used...!

Faron

Thank you for your comments. This helps!

How is the cost for the second layer of paint determined? With regards to the second layer of paint, is it needed for the walls only or for everything trim, doors etc.

His cost for materials was a little over $500 am I to assume it will be another $500 for the second coat of paint? Thanks again

Usually, the second coat of paint takes less paint. If you are painting ceilings and they are white, you may be able to get away with one coat. This is because the ceilings are usually flat. But, if you choose a different shade of white, it may not cover in one coat. For the trim, it really depends...every job is different. If the trim is already painted and you are just freshening it up, then one coat may be fine. But if it is nicked up and you have to do a ton of repairs, then two coats is best. Plus, any color change you do on the trim color is likely not going to cover in one coat. Whites cover poorly, and a lot of people choose trim colors with a yellow or cream hue which cover really poorly. I also find it strange that you are aware of how much materials cost. I would never present a bid to a potential customer that way....why do you care? Here is your one coat price...here is your two coat price.