John,

I guess you are asking if it is OK to alternate between 2X8 and 4X8 (or whatever the depth is) joists. I can't say that I have ever seen that done but I don't see anything inherently wrong PROVIDED the 2X8 is suitable for that span and loading. In other words, if the 2X8 is adequate then the 4X8 is more than adequate.

The floor will be bouncier at the 2X4 joists than at the 4X8 joists (but not by a lot - in fact it may not even be noticeable).

Why did the builder build the floor system that way? Who knows? Perhaps he had some 4X8s that he needed to get rid of.

__________________
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Bruce Breedlove
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