Subfloor Prep for Ceramic Tile Installation Entry/Bath

Hello,
I'm a newbie and would really appreciate some advice on this project that I have undertaken. I am going to try and give as much info as I can, please ask me for more info if you need it.
My half bathroom is adjacent to the entry in my house (built in 1964). Both floors were tiled previously but install was old and I don't think very well done. I have removed both old floors and am down to subfloor (I assume subfloor is the right term). Under the tile that was in the half bath, was 1/4" plywood that had to be taken out, and under tile in the entry was 1/8" thick board that was like really thick cardboard. Seemed to be similar to what game boards (like Monopoly) were made out of.
What I would like to do is tile the whole area in the same tile, hopefully tiling through.
What I was planning on doing is installing hardibacker over the subloor and then tiling on that.
I understand that I should use unmodified thinset between backerboard and subfloor, lay hardibacker, screw down, tape and fill gaps in backer, tile over top.
I have lots of questions though. Have taken pictures to help show my problems, and can take more if needed.
1. Can I tile from one room straight through to the other? Or should I make it seperate and use a threshold?
2. My subfloor appears to be 3/4" plywood, can I install hardibacker over this, what thickness should it be? What thickness is my goal before laying the tile? I would like to keep it as low as possible to avoid having huge floor height differences for adjoining rooms.
3. The subfloor is painted? Black almost to the edges, any ideas what this was for and should I apply more of it?
http://www.datazap.net/sites/tachybear/HouseProjects/edges.jpg
4. There is one patch on the subfloor where this black stuff came away with previous installation and there is now a slight depression,
http://www.datazap.net/sites/tachybear/HouseProjects/subfloor.jpg
What do I do to fix this before laying hardibacker or will the thinset take care of it? Also there are places where pulling the nails out from the previous install and left little depressions in the subfloor. Will the thinset take care of these?
5. Around the toilet in the half bath it looks like there is more of this same damage, I haven't removed the toilet yet. (Previous install wasn't tiled under it.) Will I have to replace this section of subfloor?
http://www.datazap.net/sites/tachybear/HouseProjects/aroundtoilet.jpg
The floor joists in my house are spaced 16" apart (I have a basement and looking at the underside of the floor, there is this stamp on it
http://www.datazap.net/sites/tachybear/HouseProjects/underneathname.jpg
Is my floor strong enough to handle what I'm planning?
I apologise if this is too much to be asking and please ask me if there's other things you need to know.
Thank you very much for your time.
~Rachel
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Of course you can. Just plan the layout so the cut tiles end up where you want them

1/4" cement board is typical for floors. Several brands, all work well.

instructions. this creates a new surface to tile. Ignore the paint unless it is flaking, if so scrape as required to get a solid surface.

The thinset under the cement board will fill most shallow depressions but you might want to avoid screwing the cement board at those spots so it can lay flat. Once dry, the floor will be solid.
If you had a deep depression, backfill with thinset and let it dry first, then put the adhesion coat on to apply the cement board. Same when you tile, it is difficult to get a tile to the perfect level if you are also trying to build up underneith with wet thinset. It is better to do a two step so your substrate is uniform for the tile to be set. This would be the only time you want to use rapid setting thinset.

Get all of the rotten stuff out before putting down the cement baord (substrate) and you will be fine.

some deflection. The cement board and thinset substrate will help a lot but if you can bounce the floor or it creeks considerably then another layer of plywood or reinforcement from below might be appropriate especially if you plan to use large tiles. It can't hurt to put a few more screws through the subfloor into the joists now.
Small tiles will crack at the grout lines but large ones will crack right down the middle (depending on what you have) if the floor has too much deflection. If you search the tile specific web forums you can find deflection calculators to help you understand that situation better.

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snipped-for-privacy@gmail.com wrote:

I mostly agree with the other poster, so I am no repeating all what he said.

It's a matter of taste. I would go separate with a treshold (marble or other ) in between, and would start with a full tile on each side of the treshold. Unless your most important spot is somewhere else in those rooms...

Not sure what that is. Could be some kind of vapor barrier as they did not put hardiback board down. You should be fine without adding any of that stuff.

You will know immediately when you lift the toilette if the subfloor needs repair. Consider also that hardiback board and tiles will raise the toilette quite a bit.
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snipped-for-privacy@gmail.com says...

Agreed, though it's my understanding that the floor under the tile should be at least 1-1/4" thick. I'm using 1/2" Hardibacker on my 3/4" tng plywood subfloor (tile starts this afternoon).

If there is a door, I'd use a marble saddle to set off the two rooms. In either case the tile should line up on either side.

Yes, and there is a ring made to raise the flange 1/2" and longer bolts. I've used these and then a thick wax seal. I'd taken into account the thicker floor with the toilet flange, woodwork, and doors. ...then I found the connections to the sink wouldn't reach (d'oh!). ;-)
--
Keith

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