Improve Shower Base Support

[hrsnblm]

Hello, it's been a long time since I posted last, but I am in need of advice. Years ago I replaced a bathtub with an acrylic(?) shower base and walls. Because of the location of the original drain and the drain in the base I had to build a frame which allowed me to take into account this issue.

However, after a few years of use the base cracked, even though when I installed it on top of the framing I installed a 3/4" water resistance panel to spread the weight of its use. When the base manufacturer sent out a tech to repair the crack (was still under warranty) he did a crappy job, left a hump on the floor, and it eventually cracked again.

I want to fix it permanently and am getting mixed information from my searches. I am going to replace the base but I am under the impression that 1) I need to add support to the empty spaces in the framing (filled with some compound) and 2) replace the panel with concrete backing.

Suggestions? Thank you to all who answer ahead of time.

 

[Cacher_Chick]

Most composite bases should be bedded into mortar to prevent the flexing which results in cracks.

 

[Sponsor]

 

[hrsnblm]

Most composite bases should be bedded into mortar to prevent the flexing which results in cracks.

As I mentioned previously, I had to put the base on top of a platform to account for the drain issues. When I redo it I am planning on using cement backer boards for strength and stability on top of the framing to raise the base up. So bedding into mortar is not an option.

Thanks for the response.

 

[Reach4]

1. You could rework the drain, even if it in a slab.
2. Cast iron shower base would not flex.

 

[hrsnblm]

1. You could rework the drain, even if it in a slab.
2. Cast iron shower base would not flex.

If I was redoing the wall (tiling) and all, I could look into it, but I am planning on keeping the existing walls that are part of the shower base set since my plans are to only replace the base at this time. I'm just trying to determine the best way to shore up the base with the existing framing and with replacing the support panels with the cement backers.

Should I fill the open sections of the framing to help support the new backer boards, or do I not need to worry about it? If yes, what should be used? Some type of filler (sand, a compound, etc.)?

 

[Jadnashua]

FWIW, cement board isn't actually all that strong. To get the height you want and to make the pan sit level with proper full support, do as suggested, and bed the thing in mortar. Since it's really tough to fill the voids underneath the pan and raise it up while keeping it level...you'd place piles of deck mud ( a lean mix of sand:cement about 4-5:1 with a little water to wet it like wet beach sand), set the pan in place, smush it down until it's the height you want while also level. Let that cure overnight, then finish things up. If you place some plastic on the floor (or tar paper), it will help since that will limit the floor from sucking moisture out of the mix, which, if it doesn't have enough, will not provide enough to let the mix cure properly and thus be weaker than desired or possible.

 

[hrsnblm]

FWIW, cement board isn't actually all that strong. To get the height you want and to make the pan sit level with proper full support, do as suggested, and bed the thing in mortar. Since it's really tough to fill the voids underneath the pan and raise it up while keeping it level...you'd place piles of deck mud ( a lean mix of sand:cement about 4-5:1 with a little water to wet it like wet beach sand), set the pan in place, smush it down until it's the height you want while also level. Let that cure overnight, then finish things up. If you place some plastic on the floor (or tar paper), it will help since that will limit the floor from sucking moisture out of the mix, which, if it doesn't have enough, will not provide enough to let the mix cure properly and thus be weaker than desired or possible.

From further checking and reading it looks as this is the most viable solution. Once I get the new base and tear out the old hardware I am going to put down some plastic and use the mortar to level/support the base and hopefully any future issues will be avoided.

Thanks all for your inputs.

 

[Cacher_Chick]

Right, cement board is not strong at all. If you must have a platform, you would be better off glueing and screwing together 2 layers of 3/4" plywood over solid framing.