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Mortor bed under bathtub: what about 15 years from now when ripping out tub?

10K views 6 replies 4 participants last post by  lazzlazz 
#1 ·
If I am installing a bathtub that requires being set in mortar, is there something I can do to make ripping out the mortar easier 15 years from now?

What's the purpose of the mortar? Does the mortar have to be completely bonded with the subfloor? Or could you line at least part of the space in which the mortar will be poured with something that will make a remodel down the road easier? (plastic? tyvek? some other substance?).

Can you completely line the space (in which case, the mortar would not at all bond to the subfloor)? I'm thinking "no" on this option - my thought is that at least partial bonding is necessary to keep the tub in place. But is partial bonding adequate - after all, gravity will tend to keep that mortar bed in place.
 
#4 ·
Drywall mud is not solid enough to give proper support - and is not water resistant. Please don't use it under a tub. An improperly supported tub can crack.

Just mortar and be done with it - it's no more than mortaring in tile, don't fret it. Subfloors come in two layers, if need be the top layer can be cut, removed and replaced.
 
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#3 ·
Drywall mud.....

Be safe, Gary
 
#5 ·
"Drywall mud is not solid enough to give proper support - and is not water resistant. Please don't use it under a tub. An improperly supported tub can crack." ----- Drywall mud does not re-liquidize when wet. Where would this water come from? That would be the least of my worries if the mud got wet enough to disintegrate.

"Subfloors come in two layers, if need be the top layer can be cut, removed and replaced." ----- the bottom layer is the sub-floor the top is an underlayment. http://bct.nrc.umass.edu/index.php/publications/by-title/wood-underlayments-for-resilient-flooring/

Lay builders paper down so the mortar/? will not wet the wood decking surface.

Be safe, Gary
 
#7 · (Edited)
I finally got the tub in (shower surround won't be delivered for at least a week - the first one was scratched so I did not accept it).
Since my tub needs to be raised due to the plumbing being above-floor, I created a subfloor within the raised frame so I wouldn't have 4" of mortar under the tub. The tub fit perfectly into the old frame, and once I got it in there, I decided to raise it, then pile mortar under it, rather than pull it out and somehow re-insert it once the mortar was piled in place. I raised it only about 4" with some blocks of wood and piled mortar under the tub with a trowel (took longer than simply dumping from a bucket, but I gained time because I did not have to maneuver the into place once the mortar was in place). Then I just raised the tub slightly with a couple of 2x4s, pulled out the blocks, and lowered the tub down - I had piled extra mortar around the blocks so it would squash into the void left when I removed the blocks. (Did I mention I've never done this before? The plumbing even lined up & no leaking when I poured a couple of gallons of water down the drain - true test tomorrow when I fill the bathtub!) Mixing the mortar & getting it into place was not as much of a headache as I had feared.

I put plastic between the tub & mortar, just in case - such as if I screwed something up & had to remove & start over.

I also discovered I have redwood old 2x4s (closer to 2x4 in actual size, too) in at least some of the walls of my house. They're really nice - very nicely finished. It's a shame to have them as studs!
 
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