Flooring Tile - Laying Floor tile with a ridge in the floor

I'm getting ready to put down floor tile, and I've discovered a ridge in the floor. Apparently it's where the floor has settled unevenly on both sides of a joist.
I have 1/2" backer board, and was planning on using 12" tile. If you balance a 4' level on the ridge, you get about a 1/4" gap at both ends. the floor appears to be fairly level except for this. Any suggestions?

Also, I'm doing a shower surround at the same time with 8" tile. I was planning on using 3/16" spacing between the tiles. Someone who lays tile told me that spacing might be too wide for showers. What do you folks think?

Thanks!

hey zipmn,

The sound of your floor worries me for a tile instalation. If there's already 1/4" of settling, bad things could happen when you add theweight of a tile instation. What kind of support does the floor have? Joist size, spacing, & what's the span length? Also what's the subflooring,? material & thickness. These thngs are crucial to a proper tile install.

2X10 Joist, 16" apart. 2 sheets of 1/2 plywood on the floor. Span is somewhere around 16 to 18 feet. For what it's worth, it doesn't seem to be sagging in mid-span, it's more across the joist.

sounds like a crown in the joist.You can take a belt sander to it and knock it down ,it may still be there but not so prominent you can work the rest of it out when setting the tile:cool:

I had the same problem in my house. My dinette is cantalevered out the side of the house. Where it extends outward, the floor crowned over the beam supporting the joists (not due to sagging, just poor construction). The builder repaired it by cutting out the subfloor, grinding the joist down, and replacing the subflooring. A lot of work, but I'm not sure how else you could do it. I then had ceramic tile installed over top of it. No problems - looks great.

Jim