Drill holes before or after?

[conner172]

I'm installing a brand new floor over brand new floor joists for my remodeled bathroom. The question I have is, once I lay down the subfloor, do I drill the holes for the water supply pipes and drain pipes before I pour the self leveling concrete, or after I pour the self leveling concrete? There will be a 4" hole for the toilet flange, a 2-1/2" hole for the shower drain, a 2" hole for the sink drain, and 3/4" holes for the water supply pipes.

 

[havasu]

Personally, i would drill, then pour the SLC afterwards. Just make sure to use spray foam around the holes, so the plumbing has room to breath.

 

[C.J.]

Drilling the holes through the subfloor first will be easier than trying to drill through leveler and subfloor. Drilling the holes after will make for easier smoothing of the leveler because you have no obstructions to work around.