Advice on tiled bathtub apron

[gc717]

The tiled apron for our soaker bathtub is no longer secure near the middle of the tub, although it seems fine at either end. If I push on the top of the apron near the middle of the tub, the apron moves slightly inwards and then flexes back out. Consequently, there is a slight gap between the top of the apron and the underside of the tub lip near the centre of the tub.

I'm guessing that up/down movement of the tub over the last 20 years has caused some differential moement; or that perhaps the tiled apron on cement backerboard was not attached to a sturdy wood frame. At present, there's no way to look behind the apron to see what it's attached to (if anything). Since I don't want any water to run off the outside lip of the tub and then underneath the tub to rot the subloor, I'm looking for some advice on this.

My preference is to avoid tearing out the existing tiled apron and building a new one. So far, the only thought that's come to mind is to try and shim the botton of the apron such that it fits snugly up against the underside of the bathtub lip. BTW, the bathtub lip descends about 4" vertically on the outside of the tub to mate with the top of the tiled apron. Helpful advice much appreciated. Thanks.

[Wgoodrich]

I suspect you have a plywood underfloor. If this is true keep in mind plywood is laminated in layer and will soak water causing damage such as swelling and warping of the top layer of that plywood without the rest of the plywood not yet damaged. I would go in the crawl space and look for solid plywood on the bottom of that spot. If it is still solid then you should have confirmed the top layer has become wet causing swelling and warping up in a "v" pattern pushing the till up in that spot. If this is the case you may be able to nail in the crawl space a 2x10 board against the bottom of the plywood flooring that has popped it top layer of plywood under the tile. Then once you have that 2 by under the plywood then go above and screw thin screws between the tiles through the grout in several places pulling that raised layer back down to the rest of that plywood laminent that is flat. This should flatten your bulging soft area and again make it solid for a while. If may take a few initial screws with large fender washers to pull that warp back down without pulling through the top layer of lamenent. Do this then install the permenant screws to hold long term. Caulk along the tile to tub joint to stop the water from further damaging that plywood. Then leave for about a couple of weeks. After a couple of weeks the warped layer should be retrained and you can remove the screws with the fender washers and patch the grout where those temp screws were installed.

HOpe this helps
Wg