[villagetinker]

We have a Gardenia, very similar to Begonia, and we have a removable kitty door in the center between the sliders, we just take it out when we leave.

As for the litter box, I am guessing you have the cabinet in the laundry room, we specified a laundry sink (no cabinet, and the litter box sits very well under it. I have relatives that have the litter box inside their cabinet with a hole cut in the side of the cabinet for kitty to get in and out. If the cabinet is right up against the washer (or dryer), then you could remove the doors and hang decorative curtains in front for kitty to go through.

As for installing kitty door in the wall, first, make sure the hole will be inside the lanai and NOT to the outside. Our house is concrete block, and I have found the block to be filled with concrete is several locations, so going though the wall, may include 8 to10 inches of concrete. Be sure to avoid the opening where the sliders go as you may not have clearance between the slider and the kitty door trim.

Hope this helps, send me a PM if you want to see our installation.