Do I install underlayment under the tub?

[Billy123]

I bought new underlayment for our bathroom floor. We are going to put down new vinyl flooring once we are done painting. I want to frame in for the tub today and looking ahead I have this underlayment. Anyway would I install the underlayment under the tub or just butt up to it?

[Billy123]

The underlayment is 5mm thick and in 4x8 sheets. I also wanted to ask should this be put under the bathroom counter & toilet along with the vinyl floor.

[1987Commodore]

I would go underneath with both, if only to keep water from leaking over the tub edge and wicking between the underlayment and the subfloor. same for the counter. plus, if you ever need to change the counter, you won't have to deal with different floor heights.

[Greg]

It's going to be a pain, but pull the tub and replace the subfloor under the tub. If you don't, sooner or later the tub WILL fall through the floor.

Do it once, Do it right!!!

Greg

[Billy123]

Greg the tub all ready did. I put concrete block under there and jacked up the whole wall. Rebuilt the rim joist and every floor joist in that area. Its all brand new now man. Commodore I will run both over the new 3/4 ply before the tub install. Thanks for the info.