I need some advice again. We are going to install a Repabad acrylic bathtub. This tub will be placed in a niche in the bathroom, meaning one long side will be exposed, the short side near the foot end will be against a solid wall, and the other long side as well as the head end will have a ledge about 20cm (8 inches) wide. The tub will not have a support frame but will stand solely on feet on the raw subfloor (new build with a concrete slab).
The woman from the bathroom studio, who has many years of experience, recommended building a 40cm (16 inches) drywall frame around the 20cm (8 inches) ledge, then supporting the bathtub edge up to the rim with plasterboard or Wedi panels so the tub can rest on it. The tiles will be flush, so the tub will essentially be clamped on three sides.
I asked the plumber and the drywall specialist on site today. They didn’t understand this approach at all and said they have only seen versions with Styrodur (extruded polystyrene foam) for years, which were then tiled. In those cases, the tiles would also clamp the tub.
Now my questions:
a) Which of the two options (Styrodur/drywall) is really more advisable here, regardless of cost?
b) Would the Styrodur option be stable enough so that if someone sits on the rim at the head end on an empty tub, the thin rim won’t compress the Styrodur and cause the tub to tilt?
c) Since the tub is clamped on three sides by tiles, but I read that when the tub is full, forces can occur that might slightly change its width – wouldn’t this cause the silicone seal on the long side to tear?
d) On the exposed side under the tub rim, a Wedi panel will be clamped and tiled – is damage to be expected if a person of normal weight (60-80kg) sits on the tub rim there?
The woman from the bathroom studio, who has many years of experience, recommended building a 40cm (16 inches) drywall frame around the 20cm (8 inches) ledge, then supporting the bathtub edge up to the rim with plasterboard or Wedi panels so the tub can rest on it. The tiles will be flush, so the tub will essentially be clamped on three sides.
I asked the plumber and the drywall specialist on site today. They didn’t understand this approach at all and said they have only seen versions with Styrodur (extruded polystyrene foam) for years, which were then tiled. In those cases, the tiles would also clamp the tub.
Now my questions:
a) Which of the two options (Styrodur/drywall) is really more advisable here, regardless of cost?
b) Would the Styrodur option be stable enough so that if someone sits on the rim at the head end on an empty tub, the thin rim won’t compress the Styrodur and cause the tub to tilt?
c) Since the tub is clamped on three sides by tiles, but I read that when the tub is full, forces can occur that might slightly change its width – wouldn’t this cause the silicone seal on the long side to tear?
d) On the exposed side under the tub rim, a Wedi panel will be clamped and tiled – is damage to be expected if a person of normal weight (60-80kg) sits on the tub rim there?
W
Waschtisch25 Nov 2016 08:09When installing tiles flush with an acrylic bathtub, it is important to consider that the radii on an acrylic tub are quite large and the corners are very rounded, which means the silicone joints will be wide. This is not visually appealing and is also technically questionable. Since acrylic tubs always move under load, the joint can crack unnoticed, allowing water to run freely underneath your tub....
Completely removing the old joint when renewing the sealant (maintenance joint) is likely to be challenging as well.
Completely removing the old joint when renewing the sealant (maintenance joint) is likely to be challenging as well.
W
Waschtisch25 Nov 2016 08:17How is the bathtub supposed to be filled?
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Peanuts7425 Nov 2016 09:13Does it really have to be an acrylic bathtub?
All the professionals we consulted recommended steel, ideally with a bathtub support frame.
That’s what we went with, and you can sit on the edge of the tub without any seams cracking—everything works perfectly!
All the professionals we consulted recommended steel, ideally with a bathtub support frame.
That’s what we went with, and you can sit on the edge of the tub without any seams cracking—everything works perfectly!
@Waschtisch: Then I guess it depends on the tiler to cut a nice rounded corner. Yes, I’m still wondering about the "bathtub movement" issue, whether it will actually cause a problem. That’s why I asked if it would be better to build the shelf using drywall construction; you could then attach the wall rails to it and pull the tub against the drywall — though that’s quite a bit more work than just cutting a few styrofoam pieces to size. The tub will be filled via an exposed faucet.
@Peanuts74: I prefer showering myself, but my wife takes baths more often and had specific requirements for the tub shape, which was only available in acrylic. Also, it’s the other way around for us—four doctors, five opinions. We were repeatedly advised to choose acrylic rather than steel. From a durability and stability standpoint, I would have preferred steel too, but there simply wasn’t a suitable option.
@Peanuts74: I prefer showering myself, but my wife takes baths more often and had specific requirements for the tub shape, which was only available in acrylic. Also, it’s the other way around for us—four doctors, five opinions. We were repeatedly advised to choose acrylic rather than steel. From a durability and stability standpoint, I would have preferred steel too, but there simply wasn’t a suitable option.
W
Waschtisch25 Nov 2016 11:03Is the faucet going to be installed on the front side? When used by two people, one will have the water flow hitting the back of the neck! On the long side, the spout doesn’t reach far enough.
I would also recommend constructing it with drywall.
I would also recommend constructing it with drywall.
It is a single-person bathtub. We don’t need any fancy two-seaters. We don’t bathe together. My wife prefers a tub where she can comfortably lie alone, so the faucet will be installed at the foot end.
The drywall construction will be quite complex and must be precisely fitted from the start. I’ll try to describe how I envision it, if that’s okay.
Does that sound right? It really needs millimeter-precision on the long side, especially in height, so that the drywall is flush with the frame, effectively forming the wall against which the anchors are set.
The drywall construction will be quite complex and must be precisely fitted from the start. I’ll try to describe how I envision it, if that’s okay.
- At the foot end, everything is fine because the tub sits directly against the wall.
- One long side will remain exposed anyway, where a Wedi board with tiles will go underneath the edge.
- The other long side will be the challenge:
- The edge of the tub is exactly 35mm (1.4 inches) high, which corresponds roughly to a double layer of drywall and tiles, plus there still needs to be waterproofing.
- This means I would make the drywall frame exactly as wide as the planned shelf.
- The drywall must be planned to reach just under the tub’s edge in height (the tub feet can be precisely adjusted).
- Then two layers of drywall will be installed on the frame, flush with it.
- The wall rail will be attached to the drywall frame, and then the tub will be placed on top.
- The tub will then be anchored, essentially pulling it against the two drywall panels.
- Tiles go on top, the joints are filled, and that’s it?
- At the head end, I would make the drywall frame slightly wider than the planned shelf, so the tub sits on soundproofing strips on the drywall (since it is already fixed on the long side and the foot end), and then the shelf will be finished with drywall and tiles as usual.
Does that sound right? It really needs millimeter-precision on the long side, especially in height, so that the drywall is flush with the frame, effectively forming the wall against which the anchors are set.
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