Front apron support (required or not?) for Maax alcove bathtub

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riverdale

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I am installing a Maax Exhibit 6036 IFS AFR Bathtub, in an alcove, which has an integrated apron. My question is this...

Does the front apron need to be resting directly on the floor? Along its full length? It seems to me that it would, otherwise, what happens when somebody sits on the edge of the tub? It would flex and/or crack the tub, right?

The plywood sub floor is ~1\4” out of level from one end to the other. I have installed perfectly level stringers along the back and side walls. I will be using mortar piles and plastic under the tub. When I set the tub down in the mortar, resting on the level stringers, the bottom edge of the apron will be horizontal. However, it will not be entirely resting on the floor due to the slope. One end of the apron will be on the floor and the other end will have a 1/4” gap. The instructions specifically say not to shim under the apron. This presumably is to prevent a concentrated point load, caused by the shim, cracking the apron.

Should I use some SLC in a narrow strip beneath the entire length of the apron? Presumably this will feather itself to zero at one end and be ~1\4” thick at the other. This will, in effect, give me a “shim” which is now fully supporting the front apron along its entire length.

I was initially hoping to just use the mortar to take care of the 1/4” floor slope. This would make it level but it would also result in no support for the front ledge of the tub. Perhaps the this style of tub is strong enough and doesn’t require additional support for the front ledge to be provided by the apron. As I said, the floor of the tub will be fully supported by the mortar, so I’m not concerned about that part of it.

Any advice is appreciated. Thank you.
 

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riverdale

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Taking a closer look at how the apron is connected to the underlying wood support base of the tub itself. I’ve attached a picture, and it seems the apron is connected to the wood support that runs the full length and width of the tub floor itself. I will be filling the gap beneath the tub (2” in this case as it’s an AFR model) and fully supporting the tub base this way. So it now seems to me that the apron DOES actually support the front ledge of the tub BUT it does so via the flat sheet of wood (OSB in this case). Which in turn is supported by the mortar underneath it. It doesn’t matter if the bottom edge of the apron is resting on the floor. I’ve reached out to Maax and will post an update as to what they say. In the meantime, does this seem correct to anybody out there with a similar experience?
Thanks.
 

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Terry

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The Mortar does the support on the main tub, I do shim the apron though so that it doesn't move up and down.

Piles of mortar that squish out. That way the mortar forms to the tub, and allows it to sink down to the ledgers that support at the wall.
 

riverdale

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Thanks Terry. Looking at this setup it seems I’ll be able to get mortar almost all the way to the front edge of the tub, just a little behind the apron (but not too close!). That should give it plenty of support. I’m waiting to hear back from Maax that the apron is OK when not resting on the floor. They do specifically say don’t shim it, but I see your logic behind stopping it from flexing/squeaking a little bit. Maybe a thin bead of extra flexible caulking could also work to absorb any small movements? I also have seen the advice about not butting the finished floor right up to it, again to avoid squeaks.
Thanks again.
 

riverdale

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Mmmm.....just heard back from Maax:

It is important to have a level floor prior to installation. The apron must be perfectly leveled and touching the floor. Once this is done, if the tub is uneven, you must use wood shims to be used only on the rear wooden blocks or use self leveling mortar.

You’d think that if it’s essential to have the apron entirely resting on the floor that it would mention this in the instructions, but NOPE!

Also, it’s rather contradictory advice since if the floor is level and the apron is resting on the level floor how would the tub be unlevel and require SLC?

Anyway, all that aside, I think I’m going to ensure my tub is precisely level and touching my level cleats all around the tiling flange perimeter. Then the mortar under the tub will account for the unlevel floor and keep it at that level and fully supported. I will ensure the mortar also gets underneath and fully supports the apron along its entire length. A one step process with mortar versus a two step process with SLC then mortar.
 

riverdale

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Hey “RAMROD” you asked how it worked out....

-Made sure my tub was precisely level and touching my level cleats all around the tiling flange perimeter.
-Put mortar under the tub and squished the tub down so it was touching the level cleats.
-This left a gap under the bottom edge of the apron because the tub was level but the floor wasn’t.
-Used a flexible floor patch/leveller to fill in this gap. So now the apron is also resting on a solid “concrete” support across its full length.

So far, it seems to have worked out great. The 1L tub of pre-mixed floor patch was $15 and very easy to work with.

I thought about doing this all at the same time, i.e. putting a thin strip of the same mortar under the apron at the same time as setting the tub. I decided this two-step process was probably easier and would be a less rushed way to get it done more precisely and neatly. I will be doing a 3/8” layer of SLC over the rest of the bathroom floor later for the heating mats and LVT.

I can send a picture later if you like.

Hope this helps.
 

Ramrod

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Hey “RAMROD” you asked how it worked out....

-Made sure my tub was precisely level and touching my level cleats all around the tiling flange perimeter.
-Put mortar under the tub and squished the tub down so it was touching the level cleats.
-This left a gap under the bottom edge of the apron because the tub was level but the floor wasn’t.
-Used a flexible floor patch/leveller to fill in this gap. So now the apron is also resting on a solid “concrete” support across its full length.

So far, it seems to have worked out great. The 1L tub of pre-mixed floor patch was $15 and very easy to work with.

I thought about doing this all at the same time, i.e. putting a thin strip of the same mortar under the apron at the same time as setting the tub. I decided this two-step process was probably easier and would be a less rushed way to get it done more precisely and neatly. I will be doing a 3/8” layer of SLC over the rest of the bathroom floor later for the heating mats and LVT.

I can send a picture later if you like.

Hope this helps.
Hey thank you very much for the info.

Yes photos would be amazing, I'll be trying to get my settled in the next couple days.
 

riverdale

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A couple of pics, although they don’t really show too much.

The first one shows the light grey patching compound flush with the front of the apron, filling the gap between the apron and the floor. The wedges you see are the apron was resting on while I applied the compound. Also, the protective plastic covering is still on the tub itself, so no worries about the compound running the final finished surface. I’ll be pulling them out and filling in the gap they leave behind.

The second pic. shows the roughly 1/4” gap (beneath the apron) that I was dealing with and that started this whole thing.
 

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Ramrod

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This is amazing thank you so much. I've been racking my brain on the best course of action for my predicament and it just so happens you have the same issue.

Goodluck with the rest of you renos.
 

Ramrod

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A couple of pics, although they don’t really show too much.

The first one shows the light grey patching compound flush with the front of the apron, filling the gap between the apron and the floor. The wedges you see are the apron was resting on while I applied the compound. Also, the protective plastic covering is still on the tub itself, so no worries about the compound running the final finished surface. I’ll be pulling them out and filling in the gap they leave behind.

The second pic. shows the roughly 1/4” gap (beneath the apron) that I was dealing with and that started this whole thing.

I forgot to ask. How did you measure the ledger board height while accounting for the mortar bed? Did you put the mortar bed under the whole tub or just one side?

Thanks
 

riverdale

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At first, I set the cleats at exactly the height that Maax spec’d in their instructions. However, I couldn’t get it to sit properly level when test-fitting it dry at that level. And trust me, the cleats were spot-on level. I think the problem was due to one of the legs being slightly wonky. I ended up raising the cleats about a 1/4” all around. Then when I tested it again, I got it perfectly level, and that’s where I ended up with the apron touching the floor at one end and the 1/4” gap at the other. So that’s when I figured on using the floor patch as a custom “wedge” to fully support the apron.

As far as the mortar goes...when the (dry) tub was in position and level I marked the height of the tiling flange across all the studs with a Sharpie. That way when you set the tub in the mortar you know exactly how far down you have to push the tub. Once you see your marks...bang, you should be resting on the cleats and exactly level. You can just about see my marks on the wall studs in this picture. I had also measured the height of the gap between the sub-floor and the base of the tub, and made my mortar humps an 1-2” height than that so that they didn’t end up too tall to smoosh down far enough.

Yes, except for around the drain, the mortar bed is under the entire floor base of the tub, not just one side/end. I put tuck tape on the floor to make it easy to remove any excess mortar that might have spilled over into my drain area. Since the tape surface is so slippery I figured it would not stick to it very well. I also put plastic down (a cut open thick clear garbage bag in this case) on the floor to prevent the plywood sucking all the moisture out of the mortar mix and weakening it. Then a sheet of plastic over the mortar humps to allow me to yank the tub out and start again if it all went horribly wrong.

Good luck, but it isn’t really too difficult, just work carefully and methodically.
 

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Ramrod

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Thank you again. That's everything I need now I'm going to tackle this bugger.

Good luck with the rest of your bathroom.
 

Jadziedzic

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Thanks for starting this thread; I have a Kohler Bancroft tub that also has a gap between the floor and the apron due to a sloping floor (the tub is level, though!). I'm thinking of using non-shrink grout under the lip of the apron, backing it up with a piece of wood under the tub to provide a back stop so I can pack the grout tightly under the apron lip.
 

riverdale

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Thanks for starting this thread; I have a Kohler Bancroft tub that also has a gap between the floor and the apron due to a sloping floor (the tub is level, though!). I'm thinking of using non-shrink grout under the lip of the apron, backing it up with a piece of wood under the tub to provide a back stop so I can pack the grout tightly under the apron lip.

That sounds like a good idea. I used non-shrink grout under the entire tub as the “mortar” base. It’s not cheap, but it’s good solid stuff. I was considering using it under the apron as well but decided to go with the floor patch compound. I just figured it would be easier to work with, as its pre-mixed, and do it after the tub was set, instead of trying to set the tub and fill the gap at the same time. I didn’t use a wood backer because I could see my mortar bed just behind the apron and figured the floor patch compound wouldn’t go very far.

Good luck with your job.
 
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