Complex Slopes w Hardie Board

MsRobinAMarch 22, 2012

To-For those MORE experienced than I,

A new whirlpool tub has been installed. I am making the surround/platform around the whirlpool tub using 2 layers of 1/2" Hardie board then 1/8" white FGP (fiberglass panel) on the deck-platform (and walls).

The 2X6 - 2X4 supports/framing and OSB 'decking' are in place. The first layer of Hardie Board is screwed down w Hardie screws & joints sealed w latex base mortar. The top layer - pieces are cut to size, but joints are not taped, mortared nor screwed down yet.

My question - concern is over-about sloping the final layer of the deck - platform so it 'drains' (there is a floor drain, in case)!

The deck / platform around the whirlpool tub varies from none on the full wall side where one long side of the tub touches the wall. That side is supported via 2X4 anchored to the wall studs). The three other sides range from about 21" front to back X 41" wide and 8" X 41" on the opposite end. The other side consists of a 6" wide X 3' deck with the remaing 3'+ about 2" wide.

The FGP 'should' contour to the shape/slope of the Hardie board once the adhesive sets.

To that end, UNLESS it is truly unnecessary - 'overkill', I want both end platforms to slope (concave) away from the wall toward the tub. This is especially important on the open floor side-end wall. I doubt the Hardie board will 'flex' enough to accomplish 2 'slopes'?

I've debated (w self) 'notching' the underside since even if the Hardie board cracked it would be set on a motar base then with one piece (for each side-end) of bonded FGP.

If I'm over thinking - worrying, don't hesitate to say so.



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Decking for a drop in or undermount tub needn't slope towards the tub. It's just decorative. The tub is designed to be standalone and be used with a Roman tub faucet. The tub should not have a lot of water splashing out of it, even with a strong whirlpool motor. If horseplay is anticipated, then doing a Kerdi deck would be advised.

If you are instead doing a tub/shower then you need a tub with an integrated tile flange that goes under the wall cladding so that any overspray is redirected into the tub.

In neither case would I use FRP as cladding. Tile or solid surface type material would be the material of choice.

    Bookmark   March 22, 2012 at 3:44PM
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THANKS for your reply-response. You are correct, it (the whirlpool tub) is a stand alone. No it doesn't have an integral tiling flange.

Not sure if I should have worded my question differently or it's time to clarify?

My objective - desire to have a water resistant seating / apron / support around the tub. To that end, I want to AVOID flat (level) surfaces. The suggestion that tile be used (at least on the flat surfaces, is constructive and coincidentally, there are enough large scraps of the 12" X 12" ceramic tile that the surfaces can be covered, possibly without even using the 4 full tiles that remain.

To restate, I am not hoping / trying to make the area around the tub water proof/tight, only water resistant i.e. water will run/drain OFF the surface into the tub rather than lay on the surface (FGB/tile) and/or run onto the floor.

That being said, what is the BEST way to mark, cut, mortar in Hardie board so it slopes toward the tub and away from the walls and floor?

The area at the drain end is about 41" X 8". The opposite end is about 41" X 22" and the side with the partial wall varies from 6" wide to 2" wide.

Creating compound slopes may be a 'no brainer' for those who do this work for a living / as a hobby. I've researched and read, but I have not worked with Hardie Board and tile other than on flat surfaces.

Based on what I've read (enough to be DANGEROUS) I place a narrow strip of Hardie board on the high side (against the wall & floor sides, using a notched trowel apply the mortar sloping it to the low / drain direction of the Hardie board.

Is it best to cut the rectangular (ends) in pie shape sections, before applying the sloping mortar bed and then taping and mortaring the joints after screwing down the Hardie board, before applying the thin coat for the ceramic tile?

So, pleeeeze, I seek info about the BEST way to accomplish - getting Hardie board to 'curve' / have more than one slope. I'd use the word, 'concave', but that implies a low spot vs. high on wall and floor side - LOW on tub side as in a shallow U/V the bottom of either draining away from the wall/floor behind and toward the top of the tub rim in front. Now that's about as clear as mud, but hopefully someone can - will address how best to make the Hardie board slope-contour. If it were a simple-single slope, I'd already have the project completed.

THANKS for reading and ALL additional constructive suggestions - guidance!

Be WELL & be SAFE!


    Bookmark   March 24, 2012 at 1:10AM
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I think there is a fundamental disconnect here in some terminology. A plain freestanding whirlpool tub has zero need of anything other than a simple flat deck around it. You won't get more than a tablespoon of water or two dripped on it and it doesn't need to be able to direct water back into the tub at all. What you are trying to do is completely unnecessary for any whirlpool tub.

And, on the off chance that you are attempting to create a tub/shower out of a drop in whirlpool, then you have the wrong type of tub for the job and should return it for a whirlpool with a tile flange attached. No amount of "engineering" will work to make an apple into an orange.

    Bookmark   March 24, 2012 at 2:31PM
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I get what you are trying to do. What you don't get is that it's pointless and unnecessary. In all of my years of dealing with bath renovations, I've never seen a sloped deck around a tub unless the person was attempting to use it as a shower as well---which does't work. You just don't get gallons---or even cups--of water on the exterior of a tub in a normal bathing situation.

If this isn't a normal bathing situation like your kids will be using the tub as a swimming pool, then the entire surround and deck should have been done with a waterproof membrane and then any overflow that makes it out of the tub can then just be squeegeed to a floor drain---which you state you already have. Or else this should have been an old fashioned mudbed installation with wire lathe and mud creating a sloped deck. Hardie board has to be supported 100% underneath or it will crack. It can't really do what you're asking it to do.

    Bookmark   March 24, 2012 at 2:55PM
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ALL, I never received notification regarding the appreciated follow up responses. So no, my nose (or other body part) was NOT out of joint ....

Live_Wire_Oak and GreenDesigns,

> "I think there is a fundamental disconnect ...."

Smiles AND at the same time! I'm not clear-sure how two people can be SO RIGHT, yet not! LOL

I'll try again. But, first, FWIW (odds are NOT much) no I don't plan on (LOL don't WANT) kids playing in the whirlpool as if it's an outdoor swimming pool. It isn't!

No, it's NOT a hot tub so it's unlikely more than one (possible at least in my dreams) that adult will be using it at the same time.

OKAY, given it's location, given that I could use (granted NOT very efficient, practical, NOR affordable the whirlpool tub for knee - leg - foot therapy. Since there is NO seat built in (yup, it's a whirlpool tub) if I want to do therapy on my foot, leg, and/or knee I need a place to sit.

True, I only need ONE place to sit. NO, while I'm NOT small, I'm NOT SOOOO big I'd take up ALL THREE sides of the tub! LOL

But, given that there is space between the tub and existing walls on 3 sides and I didn't think up - of anything to do with - use the space for, I figured I'd make a platform on three sides. The narrowest (opposite the full wall side, will for ease of access, provide space for the faucets & spigot since the existing water lines are on the drain end of the tub, BUT one would have to 'climb' (ok, for younger folk 'step') in the tub to turn the water ON/OFF.

Back to what I hoped to obtain answers to in my original post. In my dictionary - definitions there is a distinct and IMPORTANT difference between:
Waterproof - sealed
Water resistant - MORE likely than not to drain to-into the tub.

So based on the understanding I simply want to have a place to sit (okay, several places = at least two) and that if water were to get on any of the sides surely everyone agrees it's better the water (no matter how little/much return to the tub vs. end up on the floor.

So, rather than have ONE flat sloped plane (Hardie board under ceramic tile [nixed using FGP] how can/should one create complex slopes in/on the Hardie board which would be replicated with ceramic tile? I know the Hardie board can be cut and shims placed creating a slope(s), but not having done that before, I still would APPRECIATE suggestions - guidance irrespective of / if a free standing tub is involved.

I'll MAKE SURE to return to this forum rather than trust Gardenweb, the Internet, my ISP, and SPAM filter to notify me when the requested info is posted.

THANKS, be WELL, 'n be **SAFE!**


    Bookmark   March 28, 2012 at 4:20PM
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