basement bathroom (concrete floor drain plumbing)
 

when laying concrete over drain plumbing, e.g. for a tub, toilet, etc., i was wondering if it is customary to box some space around the fixture outlet to allow room for posterior modifications, as patcher can be filled just before installing fixtures.

or should i be sure that everything is calibrated right 100% before pouring ?

Bathtubs are generally boxed out to allow for drain connection at a later date, all others are pretty much stationary and should not need movement provided you have figured out your layout. Don't forget to wrap at least a 1/2" of foam around any pipes that will be in contact with the concrete.

thanks chris
 

which foam should i be using ? is that the only extra thing i need to do in this scenario that you can think of ?

thanks,

- a

I use sill gasket (sill seal) (The foam you put between the bottom plate and the concrete slab) Wrap it around a few times and your ready to go.

Slide the next size larger piece of pipe over your drain line before pouring and remove it once set. This will keep the pipe out of direct contact with the cement and allow you just a little bit of movement if you need it.