cement board joint compound?


  #1  
Old 03-01-04, 08:44 AM
tyanke
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cement board joint compound?

I will be laying cement board this week for our kitchen tiling project this weekend.
Can someone with prior experience explain a little what actually needs to be done? Is it similar to plastering cracks/holes in a wall? This is our first floor project, and I'm very green.
thanks

travis
 
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Old 03-01-04, 12:58 PM
J
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There are three major manufacturers for cement board: DUROCK, Wonderboard, and Hardibacker. I have use all three and have no preference. There are minor differences in the size of sheets.

The directions for installing each are pretty clearly indicated on the product, or on the web site mentioned on the product. All three want you to trowel down a layer of thinset mortar (see individual instructions for trowel size and mortar type) and then set the cement board into the thinset, and screw it down with a zillion cement board screws. The exact type and spacing of screws also varies slightly by manufacturer. Don't use an unapproved fastener, and don't skimp on the number of them.

The instructions will probably tell you to space the sheets apart about 1/16". Then use cement board fiberglass tape and more thinset to tape the joints. This is similar to drywall taping. The fiberglass tape looks similar, but is not the same so make sure you get the right kind.

The instructions will also probably tell you to leave a small expansion gap around the perimeter.

I'm not sure what you meant by asking if it is similar to plastering cracks/holes in a wall, but it seems to me that it is not at all like that.
 
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Old 03-01-04, 10:45 PM
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Hey John, for an electrician you do a great impersonation of a tilesetter.

He's right on the money all the way down the line. I use durarock about 99% of the time. Follow the directions & it's like falling off a log. I skim all the fastener heads when I'm doing the taping the seams.

Just playing devils advocate here, but you have done your homework on deflection & substrate, right?
 
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Old 03-02-04, 10:33 AM
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I was just reading a nice article on tiling a shower in the January issue of 'Fine Homebuilding'. The guy says that he attaches w/ 1 1/2" galvanized roofing nails or screws. I have a bunch of roofing nails & I'd like to use them, any caution against this?

Bob
 
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Old 03-02-04, 03:55 PM
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The manufacturer's installation instructions for most cementboards allow roofing nails. They are sure a lot cheaper and faster than the cementboard screws (from which I can only infer that the screws must have some advantage or otherwise they would not exist). Check the instructions to see if you have the right size and type.
 
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Old 03-04-04, 08:25 AM
tyanke
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cement board

Thanks for the input and information.
I attempted to calculate the deflection for the floor, but was unable to. Which measurements do I need again? It's an old house, and the joists are still solid. It'll be a first floor kitchen that I'm doing.
thanks
 
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Old 03-04-04, 12:26 PM
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Joist height, width, spacing, span, and type. Which one are you having trouble with?
 
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Old 03-04-04, 04:11 PM
tyanke
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deflection

joist span since they run the length of the house.
 
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Old 03-04-04, 05:37 PM
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It would be very, very unusual for a joist to run the length of a house without intermediate support. There should be one or more load-bearing walls and/or support beams somewhere between one end of the house and the other end. A very rough rule of thumb is that a 2 by "X" can span about "X+4" feet.
 
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Old 03-04-04, 06:05 PM
tyanke
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After I thought about it and went in the basement to look again, I realized it was from the wall to the support splitting the basement. I took the measurements and used the calculator and I'm good to go.
thanks
 
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Old 03-06-04, 11:12 AM
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What was your rating? Ceramic or porcelin tile requires a L/360 rating, natural stone, requires L/720 rating. There's a free load calculator located at this link. Deflection Calculator
 
 

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