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Unread 03-11-2008, 06:08 PM   #1
barbarapierc
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How to install backerboard-newbie

Hello, guys,
I have a house built in 1977. I am re-doing the old American Standard blue bathroom.
The floor has half-inch subfloor. I have removed old ceramic mosaic floor from subfloor and sanded to make it as smooth as possible.
I have also removed all ceramic wall tile from the cast iron tub/shower area. Underneath is ordinary gypsumboard. Some of the gypsumboard's white paper cover came off with the old tiles, and a few strips of the tape between the gypsum boards. This gypsum is in excellent condition other than its areas of missing paper and a few signs of old mildew, where gaps in the grout weren't fixed immediately. There are no areas of rot.
One "advisor" has told me that because the gypsum is in good condition I can just apply a coating of joint compound smoothly all over the wall, without sanding afterwards. Then I can install the new ceramic tiles (4 inch in white).
Another says that to be safe I should install backerboard over the gypsum board. Today I went to Home Depot and purchased enough backerboard (quarter-inch concrete board) to do the job.
I cannot find instructions anywhere on how to install the backerboard, except that Home Depot sold me the one and five-eighths inch screws. Would someone please tell me how to properly install the concrete board on the walls, over the gypsumboard? Any hints or advice? Do I need to maintain a space between tub and backerboard? I have done home repair but never attempted a re-do this extensive. Thank you so much, Barbara
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Unread 03-11-2008, 06:17 PM   #2
barbarapierc
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how to install backerboard additional info

Just want to add that I went to the site indicated on the backerboard where I was to receive installation instructions and and there were none. Barb
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Unread 03-11-2008, 06:41 PM   #3
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Here are the instructions for the hardibacker installation:

http://www.jameshardie.com/homeowner...install-us.pdf

If this is a shower/tub combo, you will want the hardibacker there as well instead of drywall.


Your subfloor has to be more then 1/2". Please verify thickness, joist size and spacing. You will want at least 5/8" thick subfloor after the deflection calculation has been met.

You only need 1/4 backerboard for the wood subfloor, and 1/2" for the walls.
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Unread 03-11-2008, 07:12 PM   #4
barbarapierc
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Clarification

Thank you for the advice. I have checked the deflection formula and found that my floor joists are more than adequate for ceramic tile (as well, there has been tile on the floor for 31 years). I understand that I will need to apply quarter-inch cement board (hardiboard) to reinforce floor before re-tiling.
However, I am not interested in removing the gypsumboard from the wall tub enclosure (previously ceramic tiled over gypsumboard). Can I just apply hardiboard to the wall over top of the gypsum board? Would the quarter-inch not be sufficient given the good condition of the underlying sheetrock? The installation instructions you kindly recommended seem to imply that the cement board is being installed directly over 2x4's, but in this situation I want to install the cement board( quarter-inch) over the gypsum board itself. In that case, would I use some kind of glue as well as the screws into gypsum board then into the underlying 2x4's?
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Unread 03-11-2008, 07:28 PM   #5
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Clarification II

I see in another post that the poster is advised to use a waterprooof membrane under the handyboard (cement board one-quarter inch). Alternatively, he is advised to use 3 coats of something called Redguard. Can I put redguard on my gypsumboard walls, then quarter-inch cement board over top? The enclosure is a 60-inch standard cast iron bathtub surround with SHOWER.
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Unread 03-11-2008, 08:56 PM   #6
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i wouldnt
you need to take it to the studs first
then you can decide on the vapor barrier
you can go with 6mil plastic behind it or redguard on the front your choice

but 1/2 is recommended on walls for the tub surround
and it needs to be screwed,tape and thinset the seems
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Unread 03-11-2008, 09:06 PM   #7
barbarapierc
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OK to Put Cement Bd over Drywall?

Under an old ceramic tile tub/shower surround I found gypsumboard in remarkably good condition (31 years tile over gypsum). Have repaired a couple of very small cracks/minor holes in gypsumboard with joint compound. Would like to install Hardy board quarter-inch cement board directly over the drywall, as I would prefer not to try to remove it (the gypsumboard, I mean. I don't think I'm competent).
Can I just apply cement/hardy board to the wall over top of the gypsum board with the special screws going into the studs? Thanks to a responder on this site, I know you're really supposed to have half-inch cement board in shower area, but would the quarter-inch not be sufficient given the good condition of the underlying sheetrock? Am confused, because the installation instructions for hardy board seem to imply that the cement board is being installed directly over 2x4's. If I put it directly on the gypsumboard instead, would I use some kind of glue as well as the screws?
Also, do I need to paint the gypsumboard with some sort of sealant before installing the cement board over it?
Also, please suggest a brand of tape and thinset and mesh to use to seal seams in cement board after installation. Thank you so much! Barbara
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Unread 03-11-2008, 09:18 PM   #8
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you can do it and some do,
you will need to use a modified thin-set and spread 100% coverage to set the Hardi in it and nail it according.

the problem you will encounter if you are not away of already is that the tile you select to redo the wall with will need to have a mud cap as part of the trim, or you will be off the wall too far for flat cap bullnose.

1/4" will be hard to install flat so I would use 1/2"

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Last edited by ceramictec; 03-11-2008 at 09:24 PM. Reason: added picture
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Unread 03-11-2008, 09:21 PM   #9
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and they recommend 1/2 on walls
they being cx
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Unread 03-11-2008, 09:26 PM   #10
guitarsman
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the radius bull nose Brian is talking about will fit better using 1/2" backerboard than 1/4". tape your seams using fiberglass tape. I usually tape my seams and corners then as I'm setting tile I will spread mortar over the tape and comb it out. This eliminates the bulge you sometimes get when you tape and mortar let dry and then set tile.
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Unread 03-11-2008, 09:43 PM   #11
cx
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Welcome, Barbara.

I've combined your threads here. Please don't start multiple threads with the same questions. It causes much confusion and duplication of effort on the part of folks trying to respond on the different threads. Bookmark this one so you can always find it again and use it for all your project questions.

Quote:
Originally Posted by Johnny
and they recommend 1/2 on walls
they being cx
The recommendations for product use come from the manufacturers, Johnny, we just try to point out what they are for the benefit of the visitors.

Hardi does actually indicate their 1/4" board for use on walls with 16" stud spacing, Barbara. I think that's a poor idea, but it's their board and your shower.

I've never seen any spec for any CBU indicating its use over sheetrock. It make sense that you could do it, I suppose, but as Brian and Phil are pointing out, you'd still do better using half-inch board even if you wanna install it over the sheetrock.

Hardi also says it's optional to use a moisture barrier behind the board. The consensus opinion among the pros here and most of the other CBU manufacturers and the TCNA is that you should use one. This would be especially important with the sheetrock behind it. In your case, I would recommend poly sheeting because it's thin and will interfere less with the installation of the CBU.

But I'd still recommend you remove the sheetrock and install the CBU to the studs. Removing sheetrock ranks as one of the easiest demolition jobs in the trade.

My opinion; worth price charged.
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Unread 03-11-2008, 09:49 PM   #12
guitarsman
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I was wondering how all those posts jumped in front of the one I originally read. thanks CX.
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Unread 03-11-2008, 10:14 PM   #13
barbarapierc
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Bullnose

I believe the bullnose tile you are referring to is what the previous tiler used on the foot of the tub/shower surround that is an exterior wall. It covered the extra barrier of gypsumboard or similar product where it stepped down to the thickness of regular gypsumboard walls. Is it a 2 inch by six inch tile? If I am correct, this bullnose is a standard tile at home centers?
OK, you have convinced me to try to take off the drywall. I will go on line and look for instructions on how to remove gypsumboard from studs. Unfortunately, I will somehow have to cut the gypsumboard horizontally on the longest shower wall, as I do not plan to tile all the way to the ceiling. Is this a customary problem? I have normal tools including extra-long level and chisels, etc. Do you just gouge it out and chisel it off the studs (I assume builder would have used glue plus screws or nails). If anybody has a simple answer on removing wallboard and cutting it away horizontally, I would appreciate it.
If I can get the gypsumboard off the studs, should I install cross piece 2 x 4s in between the vertical 2 x 4s that exist in order to have more wood surface to nail the cement board into?
I was planning on cutting the quarter-inch cement board with a regular hand cutter (the replaceable blade box cutter thing that everybody uses). What specific tool do I buy for cutting cement board in the half-inch thickness? I have got the faucet handles and tap spout off the wall so that I can conceivably cut holes in the cement board for those three pipes but need to know what tool will cut the holes and trim the long length both.
I am pretty strong but know I can't hold a 40 lb sheet of cement board in place to the wall while holding the drill that is screwing it into the stud. How do you hold the cement board to the wall while installing when you are working alone?
Also, do you slip a thin piece of continuous wood along top of tub to create a narrow opening between cement board and tub?
Are instructions available for installing a vapor barrier like the plastic you-all mentioned on the site somewhere? I assume you don't use glue under the half-inch cement board if you are using a plastic vapor barrier.
I live in No Virginia and am wondering if anyone wants to suggest a different (better) cement board than the half-inch hardy board.
Thank you all so much for the advice!
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Unread 03-11-2008, 10:51 PM   #14
guitarsman
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I use a stud finder and mark the studs close to the edge of the tub. then draw a line down the center Then cut down the center of the stud, the top I use my level and draw a line around the three walls to my stopping point. I use a utility knife and cut all the way through, then use a pry bar and carefully remove the drywall. If there isn't a stud next to the edge of the tub I will add one. and screw both the drywall and backerboard to this stud. It's pretty easy to do.
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Unread 03-11-2008, 11:26 PM   #15
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Quote:
cut the gypsumboard horizontally ...I do not plan to tile all the way to the ceiling. Is this a customary problem? I assume builder would have used glue plus screws or nails.
Totally common issue, and not a problem at all. If I want to tile up say 6'. I measure up 5' 9" or somthing similar. Make my line on the drywall and cut it with a razor. Then I run my tile up so that the top tile extends that last 3" onto the sheetrock. I would be amazed if the builder had glued down your drywall, it should just be nailed up there.

Quote:
should I install cross piece 2 x 4s...?
You can if they are needed, or if you just want to give yourself an extra nailer. I will double up a stud where a joint will be, or in a corner just to give more room for fasteners. Will run one on its side where there are seams. This is also the time you want to put in blocking/studs for screwing in shower door tracks, grab bars, etc.

Quote:
I can't hold a 40 lb sheet of cement board in place to the wall while holding the drill that is screwing it into the stud. How do you hold the cement board to the wall while installing when you are working alone?.......am wondering if anyone wants to suggest a different (better) cement board than the half-inch hardy board?
I would consider one of the foam based backer boards such as Wedi or Easyboard. They are extremely light and would suit your situation very well. Not as common as Hardi or Durrock, but if you can find them it would be worth it in my opinion.

Quote:
Are instructions available for installing a vapor barrier like the plastic?
Use staples. Let the plastic drape into the tub until the backer is up, then trimmed the excess off with a razor. (If you use more than 1 piece, overlap them so the top sheet drapes over the lower sheet)

Quote:
I assume you don't use glue under the half-inch cement board
Correct!
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