Bumpy bathroom subfloor, what to do?

Hello,
A while ago my dad decided to refloor his bathroom. He pulled up all the old tiles and left the subfloor. The subfloor which seems to be made out of particle board and 1xX boards was rather stinky (not toilet stinky but cutback? adhesive subfloor stinky) so I get the bright idea to help him by covering it with some cementious underlayment (used Armstrong S-184 i think) because he'd been inhaling that floor for over two weeks while deciding what tiles to get or whatever reason. Anyway, I did a lousy job and now the floor is bumpy. I been knocking off high spots with a chisel, but I despair of getting it flat. Any ideas on how to proceed? (Bumps are noticable when tiled over).
I thought about using self leveling underlayment. Home Depot now has a new Henry product, but it looks like my subfloor doesn't meet the spec (particle board seemed to swell up as high spots) and Lowes had some Lactirete product, but apparently they don't carry the primer for it.
Another idea some random guy told me was to put down luan over the floor, not sure this is a good idea to have in a bathroom ... won't the layer act as a moisture trap, and not sure it'll do much for the bumps.
The last idea is to rip up the subfloor and replace the boards with approved subflooring (and forget about the underlayment) which I guess will be expensive. I have no problems with taking the toilets out (it'll be the 4th time <sigh>), but I worry about matching the subfloor height with the bath tub (which I will not take out) level, plus I really don't want to replace the subfloor.
The bathroom area is about 75 tiles so I guess <75 sq. ft worth of flooring. Any ideas or suggestions?
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On Wed, 29 Mar 2006 07:16:37 GMT, idiot for helping out

A bathroom is probably to small to use an orbital sander on, so I'd take a belt sander and really aggressive paper to the high spots.
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A concrete brick makes a great sanding block for cementitious materials of any kind.
The square shape allows you to grind 90 deg angles at the edge of the floor easily and the weight helps grind the floor flat.
A belt sander would work well too but is easier to cause more imperfections by itself (mostly pits).
Ultimately it depends on what flooring he chooses. If Vinyl, you'll need a perfect substrate but if 12" tile, you can accept a lot more pits but few peaks.
You'll need to worry about matching floor height anyway once a flooring material is chosen. You may ultimately want to rip it all out and replace with 3/4" ply with cement board on top. By adjusting the plywood and cement board thickness, you can get a range of floor heights with just 2 or 3 layers. If there is any deflection in the floor now, you'll need to do this to prevent grout cracking in a tile job anyway.
For a bathroom floor, go with ceramic or porcelain tile. Easier and cheaper than stone. Too many size and color choices to imagine. Price as low as $1 SF to "skys the limit".

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It's going to be a vinyl floor. I thought about the sanding, but couldn't find any suitable sandpaper (I was thinking medium grit wet/dry paper). The cement brick sounds like a good idea, do you use sandpaper with it or just the block?
Personally I'd do ceramic, but I think my mom vetoed it as being cold on the feet.
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Just the brick all by itself, wash it with a hose when the pores get clogged.

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They make something better than the brick. I think you call it a holy stone. About the size of the brick, black and comes with a handle attached. Works much better than the brick.
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Good luck looking for "holy stone" on google.
I messed up the search and came accross: http://www.sjdiscounttools.com/jlmht2.html
How, just HOW do they get away with naming their product the "Holy Terror Sanding Block". Wow.
-Kevin
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yeplace subfloor oir you WILL be doing this job again:(
Personally fix it once fix it right then go relax is better than patch it and do it over later...
maybe its just me?
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