installing shower kit on hardwood

[bootzila]

I am in the process of installing a Kohler shower reciever, walls and door in my half bath on the main floor of my house. It will only be used by guests, and I was planning on installing it on top of my 3/4" solid oak prefinished floor. However, the floor is not level and now I am trying to figure out how to put down a mortar mix in the corner, preferrably without removing the finished floor first. I have thought about simply laying a piece of 1/4 inch Backerboard down without anchors or adhesive and then making a thin set mortar bed on top, using flexible mortar. My concern is that the finished flooring will expand and contract over time, and twist up and down in the process. This will crack the mortar if directly on top and distort the Backerboard if it is secured directly to the oak. What else would should I consider, and are there any options that people have tried in this circumstance?
Thanks in advance,
Greg in Vermont

[hj]

A lot of people regret putting a hardwood floor under their toilets, I cannot imagine what will happen with a shower on it, especially since it is almost impossible to not have some water escape through the door opening every time the shower is used.

[jadnashua]

I'd cut the oak out of the area you want to install the receptor, depending on what's under it, you could add plywood if necessary, and then reinforce the floor with the mortar to make it set level and at the height you want.

[hj]

Again, most installers would remove the wood around, or at least in front of, the shower and install tile there.

[bootzila]

The floors in this bathroom have been down for at least 10 years, and the toilet has never been a problem. My first floor has it at three of the four doors, and while the wood is a little worn and scratched in spots, the snow and rain that is tracked in has never been a problem. Moisture from the basement in the summer combined with the temp increase does make the floor swell a little, but it settles down quickly in the fall.
Even if I were to rip out the flooring under the shower and surrounding area, and lay down a tile rim around the shower, the hardwood that would meet the tile could still swell with moisture, pushing the tiling, causing it to crack and fail. I think if I were to do this I would want to do the whole room as it seems like the only thing to do to prevent this, as the grout between the tile and the wood will eventually fail and allow water underneath the floor. The bottom line is that this shower unit will be used 15-20 times a year max. It seems that the moisture impact to the floor is not any worse than me coming in from shovelling snow, and tracking into the bathroom, which does not produce any problems. What is the worst that could happen if the mortar bed cracks? Could it crack the reciever?

[hj]

If it is upthrust and cracks, then the shower floor will probably also be lifted.

[jadnashua]

The (small but important) movement of the hardwood under the shower could end up stressing the drain connection, the door assembly (assuming you have a door vs a curtain), and any tile thatmay be on the walls. Hardwood just isn't stable...plywood is much more. Unless you have a leak, occasional water on the floor from tracking it in or maybe dripping while drying off probably won't be a problem, but if the door or curtain regularly allowed mositure to get to the wood, you'd end up with problems. It is best to minimize potential movement - this includes things like the shower and a toilet.