Originally Posted by AgentW
This is absolutely true. Though, a lot of times, I've found this is because something was done incorrectly before that point so, to account for that, a deviation needs to be made.
The only one who knows for sure is the framer, but I can tell you, plans are never perfect.
Of course it does. If joists are placed at 16" or 24" O.C. from back to front, rather than front to back, and that front to back dimension is not evenly divisible by those O.C. placements, the joists will end up in different places than originally designed.
I've rarely had plans that specified a joist layout, unless it was designed by an I joist company and they rarely, if ever in my experience, make accomadations for plumbing.
That means, if a builder and a plumber (in this case, me) are given the designs and I design my drainage and venting based upon the joist layout as designed, but the builder decides to do his own things for no reason other than "that's how he does it", without taking into consideration how those changes will force others to rework their designs, then that's a problem. It caused a joist in the WC to fall directly beneath the drawn toilet, forcing me to move the toilet much further off the wall than I wanted. I also had to rework the drainage to account for this change.
I always take considerations for drainwork and wet walls, which, again, are rarely if ever, specified on a set of plans.
A good framer will walk away knowing that you, the plumber, will breeze through the house without joists or studs in the way. That's how it's done correctly. Now find a builder who is willing to pay for a good framer who takes the time to do his homework and you may find me on one of those jobs. Joist layout should not be left to chance. The framer is responsible for laying out for you guys. Trust me, just because it's on a drawing, doesn't mean it works.
It didn't mean it couldn't be done. It just meant that I had to do more work because the builder "does what he does", regardless of how his work affects the next person who comes in and has to work with it. If the joists are drawn front to back, then that's the way they should be built. Doing it the other way is either a sign of apathy, or poor attention to detail.