possible to add mortar bed after tub install?

[Lou_MA]

hi

i had a new fiberglass tub installed, and it wasn't set in a mortar bed, although it was supposed to be according to the installation guide. it seems to flex slightly, so i would like to add a mortar bed (or other support) if possible.

the bottom of the tub seems to have a grid-like surface, along with two metal brackets that swing out and seem to brace the outside face of the tub.

because i'm also having new drywall installed and some of the panels have yet to be installed, i do have access to underneath the front of the tub.

does anyone have any suggestions on if it's possible to fix this without doing a tear-out (since the drywall around the tub has already been finished)? i was thinking about just trying to push some mortar in wherever i could reach. could i also use foam? if so, what kind? just something like great stuff?

thanks for any advice

[Brad Denny]

Hi e,
Don't take this to the bank, but the foam might work for you. I bet you could put two or three of the little nozzles together with a little effort to shoot the stuff toward the back more. I would put some weight on the shower floor though because the foam really expands. I've seen it raise bathtubs off the ground.

[Lou_MA]

hi brad, thanks for the reply

if foam expansion is an issue, should i use the windows/doors great stuff that won't expand? or do i then have to deal with the foam not expanding "enough" to fill the voids?

[ddmoit]

Originally Posted by econguy

i had a new fiberglass tub installed...

Did you hire someone to install it? Any chance of getting them back to do it right?

Lou, how about clicking on the User CP button above and editing your signature line to include your name? That way, it will always appear at the bottom of every post. The friendly folks around here like to know who they're talking to.

[Lou_MA]

don't want to go into details, but at this point, i'd rather try to fix it myself...

[Davy]

We use to use the foam (triple expanding) until we had problems with it lifting a tub up off the deck. The tub was full of water at first but during the night it seeped out very slowly and by morning there wasn't enough water in it to hold it down. If you can reach all the way to the other side, I'd use the cement.

[jadnashua]

Fill the tub with water to hold it down and use the low-expansion stuff. You still might have lifting problems. If it is like a grid, or has dividers, try to fill all of them.

Econguy,

We just did a new tub surround for a customer that didn't have the budget to tear out the tub and reset it. It was creaky and rocked a bit, and we put about 6 cans of the low expanding foam (that is used for around windows) under the tub from both ends and along the back. By doing it slowly, one can at a time, we got the tub to be about 95% better without the tub lifting off the floor.

Be careful using those spray foams-wear gloves and safety glasses.

[Oebur]

I've used a grout bag to get mortar under a tub. We were fixing someone elses mistake, and it worked really well for us. Just a suggestion of course. I think the minimal expanding foam with water in the tub for good measure is a good choice as well.

[holybuzz]

I don't think that the foam will give you the dull thud you'll get from cement (if you can get enough cement in there, that is.) I'd mix it thin and fashion some kind of pushing paddle (scrap wood) to get as much as possible in there. Then, if you can, put something down that will prevent it from flowing away.

BTW, after it dries (foam or cement), put as much insulation under the tub as you can (I used old cellulose that I'd replaced with pink). It cuts down on the sound and heat loss.

Keith

[Lou_MA]

hi everyone,

thanks for all of the feedback. i'll give the low-expanding foam a try, and keep my fingers crossed.

thanks again!

[drake4646]

Did the foam work? I have the same problem with an americast tub. I have acces on the drain end but thinking of opening up the other end and trying to get cement in there. Not sure how I'm going to do it.

[rmckee84]

Not to say its right, but I've done it with good results. Like everyone stated, fill it up with water and use the low expansion type if you go the foam route.

[Davy]

You might could rig up a long straw that would reach way back under the tub and use the canned foam. Like Ryan said, the low expansion type.

[drake4646]

What about putting thin set mortar in a plastic bag the size of the tub underneath and then push it under. Once there one could squeeze the mortar tight to the tub from the open side of the bag. I have the drain side open only. I have an American standard cambridge tub. The directions say mortar is not necessary but I would like to get some in there