depth of the rough-in valve

Hi all

What is the best to calculate the depth to install the rough in valve for a shower handle? How accurate do we need to be?

In my old shower, tiles was installed over a cement wall (with a lathe) which was attached to green boards. I would say both add up to about 1" of thickness.
I took it down to stud and I plan to install tile on a 1/4" cement board.

Do I need to push the valve further in the wall or the shower handle trim can compensate for that?

Thank you

First, while a few brands of cbu allow 1/4" for walls, most pros would not use anything other than a nominal 1/2". Then, without knowing what brand and model, it's impossible to tell you where the rough-in valve has to be - sort of like asking how high is high, or how fast is fast. If the mud guard is still attached (they may have thrown it away), it will usually have min/max lines on it to show where the trim will fit. Note, one end or the other may not actually LOOK good to you, but it will fit. If the valve is too far in the wall, some companies make extension kits. There's no easy way to fix one that's too far out. Basically, attach the trim and see what the gap is between it and the valve, then make the wall-valve spacing the way you want it.

It depends on the valve.

Some of the Home Depot stuff years ago had a tollerence of 1/8"

Something like Moen may have 3/4", and if they are too deep, you can get an extension.

Kohler has some shower stuff that has to be within 1/16" to fit properly! Most allow you more tolerance. But, as I said, you may not LIKE how it looks, but to the manufacturer, if it fits, it's okay in most circumstances.

Your ONLY guide as to where to set the valve is the manufacturer's max/min dimension. Any where between those two dimension and the trim will fit properly. if it is too shallow, you may be out of luck, but it it is deeper, but not TOO deep, there may be an extension to make it fit.

Thank you all. I will have to push the valve deeper in than since my walls will be thinner. No big deal.