Bathroom floor tiling question

Okay, here's the situation. We pulled up our toilet in preparation of laying the backerboard and then the new tile floor. However, when we did we discovered that some time in the past (had to be before we owned the house) there was sufficient leaking around the toilet to destroy the flange and also caused some water damage to the vinyl floor's underlayment (particle board). 90% of that board is good a solid, but where that leak had occurred there is some minor swelling. We had to cut out part of the flooring around the toilet plumbing to replace the flange properly, and when we replaced that piece that we pulled out, we find that the swelling makes the floor on the one side of the repair about 1/8" higher than the replacement.
Questions: Must we cut out more of the particle board and replace it, or would sanding it down level be sufficient? We intend to put backerboard down, but because of where this is (small bathroom - can't get under the cabinets) we don't want to have to take up the whole piece of underlayment (particle board). I'm thinking that some elbow grease and a good sander should level it off. Any thoughts?
TIA
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
L Beck wrote:

1/8" is a lot to sand off. What about building up the other side an 1/8"?
Rich
--
"You can lead them to LINUX
but you can't make them THINK"
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
I would pull the cabinet and remove all the chip board. Then install plywood floor.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

It makes no difference. You have correctly identified the problem and it gets fixed either way, so choose which one you feel most comfortable with.
PJ
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.