View Full Version : Missing mortar bed for tub

08-15-2008, 09:25 AM
So, I have a small problem on my hands. We bought our house last November and the whole house had been remodeled. I am a contractor and we searched the house over and it all looked good. Well, after moving in I happened to be in the garage attic and peeked through a small opening behind the new American Standard Plebe whirlpool tub and noticed the entire floor was floating.

I tracked down the plumber who had done the work for the previous owner, an older gentleman who has been a licensed plumber in GA for 30 years. Needless to say, he said he has never put in mortar beds under tubs, and nothing came of the conversation. Well, about 2 weeks ago, I began noticing water damage on the ceiling beneath the trap. I have now removed the tile wall that was installed to cover up the tub wall in the bathroom. I found the leak and had to tighten the fitting. But, the entire tub bottom is sitting off the subfloor, over 1" at the back of the tub.

What would be the best way to add support under the tub? I realize the expanding foams are not stiff enough. I thought about cutting some wood shims and then filling mortar in between, but didn't know if this would work? It is possible to gain some access through the attic that is on the back side of the tub. That would provide access from both sides of the tub. I plan to replace the bathroom side of the tub enclosure with a full removable panel to provide future access. My wife and I have discussed changing it all out down the road to a step in shower, but do not plan to do that now, so I am just looking for a proper fix to give us a few years of fix.

Some pics of it for reference


Master Plumber 101
08-15-2008, 12:04 PM
I viewed the pics. and think you may be able to support that. When I set tubs,wirlpools and shower bases I use Gypsom plaster. Home Depot usually has it and you can find it by the drywall supply section. Get a mixing padel 5gal bucket and a drill (i use my right angle drill) that with stand low speeds with a lot of torque. Mix it and fill in all the gaps under tub, when it sets up it will be very solid. Make sure when you mix it you have a thicker consistency so it does not just slide off the padel. Hope this helps.

08-15-2008, 12:13 PM
I had figured the plaster would be best, as I have used it when setting 2 molded shower bottoms. I guess my main concern is if I will be able to adequately shove/push enough plaster under the chipboard piece to provide proper support.

Master Plumber 101
08-15-2008, 12:15 PM
I think so. I had a few jobs where handyman set the tub:eek: and had to respond to the same thing.

08-15-2008, 12:21 PM
Great news for me. I look forward to getting it fixed. Then I will have to make my removable panel, as I hate to tile back over access to the plumbing yet again.

Master Plumber 101
08-15-2008, 12:23 PM
Please post again, attention Master plumber101 to let me know if this works for you.

08-15-2008, 03:25 PM
It doesn't take much for support. It is nice to have something there.
Even a few places will help.

08-15-2008, 03:52 PM
Think of your floor...normally, joists are on 16" on center, then you've got probaably 3/4" plywood anchored there well to provide support between the joists. In most tubs today, you're dealing with maybe 1/4" thick plastic that is nearly 5' long...it WILL flex if you don't support it. Some come from the factory well supported, most don't. None of that matters if the floor isn't flat and level. A mortar bed fixes most problems.