[onmywayup]

Is there any difference in the actual dimensions (not the nominal dimensions) of 5/4 cedar decking, as opposed to pine?

I just pulled a few rotten cedar floorboards out of a deck and since it's eventually getting covered with a solid stain, customer asked if I could save a bit of money and throw treated pine in it's place.

 

[mski]

There might be a slight difference depending how wet the PT wood is. The drain gap between the boards may not be there until after the boards dries out.
Take a tape measure with you when getting the boards and find the driest/ narrowest ones.

 

[griz]

There can be a great deal of difference between mills & different mill runs.

 

[Deckhead]

You could always say, I've never done that and don't plan on it. You're asking for trouble when you start stepping over dollars to pick up dimes.

 

[Calidecks]

Hell, I can get different sizes in one unit, let alone, in your case, where they probably came from different mills.

 

[onmywayup]

Very interesting gentleman, all good info.

I reckon we'll just stick with cedar on this one.

 

[Morning Wood]

Buy 2x and plane it down.