bathroom remodel [Archive] - Ceramic Tile Advice Forums - John Bridge Ceramic Tile


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09-25-2001, 01:17 PM
I'm helping my son remodel a small bathroom. We're done with the demolition - took all the tile off the walls and got the floor down to a 1/2 inch plywood subfloor.

We're putting a shower surround on the walls above the tub, wainscotting on the other walls, and a tile floor.

Can I use 1/2 inch cement backerboard over the 1/2 plywood? Is that enough? The room is about 8 x 5. Taking out the tub area, I'll be tiling a 5 x 5.

Also, any suggestions on how to clean the rim of the tub where all the caulking has been for many years. I'm having a hard time getting it all off.

Thanks so much for all your help!

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09-25-2001, 03:51 PM
I had the same situation with my sub-floor. Backerboards are not structural material. I glued and screwed 5/8' ext plywood down per the TCA handbook instructions and topped that off with 1/4" hardibacker. This is assuming you have the proper joist spacing and support.

I'll step back in see what the Pros say now.


John Bridge
09-25-2001, 04:17 PM
I think Dano said it pretty well. The half inch won't make it with any kind of joist spacing. You'll need to add some plywood and then the backer.

Getting off old caulking is a bear. After wearing out our fingers using razor blades over the years we've narrowed down the options to one. We use the "Zip" knife floor scraper with a brand new blade. Be careful to keep it at a very flat angle to the tub. It's easy to scratch things up.

Bud Cline
09-25-2001, 04:30 PM

Most automotive parts stores sell a razorblade scraper that holds a single edged blade as do the others. The difference is this scraper folds into itself. When fully open it provides a very substantial handle. You have probably seen auto inspection stations using this type of scraper.

I tell you this (trade secret) because these scrapers cost considerably less than the floor scraper John talks of and the blades are cheaper also.

Don't spread this around though because these guys will know all my little secrets before too long. Well not all of them because I will never talk about Veronica.

John Bridge
09-25-2001, 04:33 PM

09-25-2001, 05:35 PM
The underlayment that we took out was 1/2 inch and vinyl on top. I guess I'm a little concerned about 1/2 inch subfloor, plus 5/8 plywood, plus 1/4 hardibacker, plus tile (1/4 or 3/8). The concerns are (1) the doorway - will it be too much of a lip into the room and (2) will the toilet go back on without having to have a plumber do work on the flange.

Can I use a thinner plywood? Now don't you guys get too upset by what I'm about to say. The guy I asked at Lowes today said the 1/2 hardibacker would be fine because it is much stronger than plywood. He said 1/2 hardibacker equals 1 inch of plywood. Of course, I wasn't going to take his word without confirmation from you experts here.

Thanks for the tips on the tub. John and Bud, I actually have both of those scrapers from previous jobs. I use "I" rather loosely. I'm really only the project manager...I get my husband and sons to do most of the hard work!

Bud Cline
09-25-2001, 05:53 PM
I'm not going to waste a lot of my time providing you with the specifications of plywood as compared to Hardi-backer, so suffice it to say the guy at Lowes is nothing more than a rectal orifice.

The absolute minimum (if your structural components measure up) of your subfloor is 1-1/8" (before tile). This should include cement board. So if you want to split hairs then you could use an additional 3/8" plywood atop your existing 1/2". If your structural components measure up.

We may tend to overkill here but believe me you'll be better-off if you use the 5/8". If your structural components measure up.

The transitions can be a problem but only a minimal one, we can handle that.

The toilet? We can handle that too, no big deal.

Now let's go here we're burnin' daylight!!!

Rob Z
09-25-2001, 06:50 PM

It's hard to follow up on that last one.


Bud Cline
09-25-2001, 06:58 PM
Too late. Now the suns gone down, oh well we can start tomorrow.

09-25-2001, 08:43 PM
There was a tip in one of the "home improvement" publications on how to remove old caulk. I have never tried it but it couldn't hurt.

It seems that acetone (aka fingernail polish remover) does a pretty good job of removing caulk. The trick is to soak a cotton cord or rope in acetone and then place the cord along the caulk line around the tub/shower. Secure the cord up against the tub/wall by using aluminum tape. Let this sit 24hrs or so and then wipe off the caulk. This sounds a little too easy but it beat the scraping if it really works.


09-25-2001, 08:46 PM
"...1/2" hardibacker equals 1" of plywood" HMMMMMM!!!

so much for "we have experts in all depts"

I guess we'll be using CBU for the roofs and floors soon if Lowes is correct


Bud Cline
09-25-2001, 09:05 PM
This is just a guess but being familiar with the use of acetone as it relates to laminate top manufacturing for twenty-five years I can tell you that a cord (ie:clothesline rope) soaked in acetone would "flash off" within the first ten minutes.

Someone please convince me this method of caulk removal is a workable one.

.....and foil tape? Wouldn't the fumes from the acetone release the adhesive on the tape in a short time? Oh here, I can answer that question. YES. To say nothing of the cost of a small roll of foil tape. WOW!

Speaking of fumes.....oh my God, acetone fumes are as volitile as any fumes produced by any solvent.


09-25-2001, 09:21 PM

There are products available at hardware stores that remove silicone.One that comes to mind is called "Goof-Off",no really.A customer told me it works.But make sure it is O.K. to use on the finish of the tub.

I have an old fashioned maple scraper that is quite sharp considering it's made of wood.These work well to remove mastic and mortar from fragile tiles and surfaces.

You should look into the Ditra product from Schluter.It's an isolation membrane and waterproof underlayment for tiles.If you're concerned about height at the transition.You'd still have to install more underlayment than what you have now though.

Maybe someone could post a link to Ditra.I am certifiably useless when it comes to computer tech.Can lay a mean tile though.

09-25-2001, 09:29 PM

You make many good points....

I'll try to find the article and see if I've missed something here.


Bud Cline
09-25-2001, 10:03 PM

This may well be a valid procedure but sure sounds risky to me. I can't see it doing anything but wasting time and money.

How much do single edged razor blades cost anyway?

Bud Cline
09-25-2001, 10:09 PM

[Edited by Bud Cline on 09-26-2001 at 12:16 AM]

09-26-2001, 03:11 PM
I am thinking of using 5/8 plywood and then Ditra. Would I nail or screw the plywood down and do I need to also glue it? How easy/difficult is the Ditra to work with?

Thanks for your help.

John Bridge
09-26-2001, 03:20 PM
By all means, glue and screw. It strengthens the subfloor considerably.

09-26-2001, 07:51 PM
Yeah I get the picture. I guess if the fumes didn't get ya the stuff might work. I personally have used the single edged blades on numerous occasions to remove silicone based caulk. For caulk that has become hard and brittle, I find an old chisel works fairly well as a scraper.

I seem to have several old chisels that I've ruined scraping up excess thinset.

There is a product at the home improvement stores called "caulk B-Gone". Any experience with it?. Possibly another gimmick.


03-20-2004, 09:07 AM
I have noticed some people asking how to remove toilet flanges during a remodelling or repair job. The standard reply has been "get a plumber". However, if the material you're dealing with is PVC sch 40 or sch 80 or maybe even ABS, the ideal solution is a tool called the PVC toilet flange cutter and remover. It's an attachment to a hand drill. It chucks to your drill and cuts out the flange from the inside. Then you can use a union to extend and cap or simply extend and re-flange. If you need more info just knock and i'll try dig up their site and address and phone and such;)

John Bridge
03-20-2004, 07:47 PM
Hi Seth, Welcome aboard. :)

Thanks for the information. That tool is sometimes called an "inside cutter." :)

03-21-2004, 08:05 PM
Yep, I even posted a picher of one once upon a time, but I wouldn't have no eye-dee how to find it. :)

03-22-2004, 08:38 AM
Hi John Bridge: I am familiar with the tool you mention and If not incorrect the "inside cutter" you speak of is a manually operated tool. Am I right???? Well the device I meant to describe on my original posting is a drill attachement tool that chucks into your hand drill just like a bit. It operates at high velocity (used preferrably with a high rpm drill, i.e. 2000 rpm or greater) and is designed especially for cupping into toilet flanges and removing them by cutting from the inside. The whole operation takes maybe 2 minutes. If you want more specific information write back I'll try to e-mail you some literature I have on how to get one.

12-09-2007, 03:37 PM
I have a blue bath with some white spots and dolphins at closet and carpet... It looks clean but I want it to get some life.. what should I add to it? should I change the color?