Complex Slopes w Hardie Board
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.