My contractor is putting 3 coats of polyurethane on our hardwood, 2 coats of satin and final coat of semi-gloss. We want a semi-gloss finish. Is the final coat the only one that matters for the sheen or should they all be semi-gloss?

The first two should be high gloss not satin. The final coat should be your sheen coat.

Well, they've already put one coat of satin and they are coming tomorrow to put another coat of satin. How detrimental is this? Can you give me any advice for negotiating this point with him? In other words, why should the first 2 coats be gloss and not satin?

Thanks much for your help.

All poly starts out as a high gloss product then diffrent amounts of a flatting agent are added to dull down the sheen. The catch is too many layers of satin will create a hazy/cloudy finish. I would put gloss down on the next coat then final it with your desired sheen. it will give a crisper looking finish. btw it's your floor they shouldnt have any problem with putting down what you want, I would let him know before he showed up to do the job so he can be prepared and wont cause and unneccsary delays.