# Base choice for tile arch



## J Hawkes (Dec 31, 2006)

Hey everyone, this is my first post here so go easy on me.

I am finishing a bathroom I've got the square framing for a door to a walk in shower I want to tile.  I want to make an arch in the door way ceiling, then tile it.  I've heard a couple different ways for the base and would like some advise.  I've read that I can use 1/4" sheetrock doubled up and soaked wet, then secured in place in the arch and let dry. I've also been told I can do this same thing with 1/4" plywood.  If either of these are right, which one is the best? If neither are right, what is the best way to tile an arch? I hope I've given enough info.


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## Square Eye (Dec 31, 2006)

1/4" plywood only bends well for me when I try to stand it on end. 

Drywall will work, but wouldn't be the best choice for a damp location like a shower.. My best results have been with 1/2" plywood scored across the back with a radial arm saw.

When finished, it looks like this;





I doubled it to make a smoother job of it. May not be necessary for tile, but may be necessary for strength, I glued them together and nailed it in place.

A closer view;


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## J Hawkes (Dec 31, 2006)

Thanks, I really like the photos.  Looks like you scored it more than half way through, and about every 1 1/2" or so.  I'll have to try it, I've got some 1/2" plywood. Thanks again.


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## Square Eye (Jan 1, 2007)

That's scored closer to every 1/2 to 3/4"..
The scores have to be very close to evenly spaced, for the wood to bend evenly. 
The closer the scores, the tighter it can bend.
And yes, they are cut more than 1/2 way through.


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## Bud Cline (Jan 4, 2007)

Drywall wouldn't be acceptable at all.  The plywood would only be acceptable as a base (substrate).  Moisture will destroy either in short order.

You can form the arch with wood members then cover the members with a cement board called Hardibacker.  Half inch Hardibacker will conform to the curve if I am understanding what you want to do.  All surfaces should be covered with Hardibacker and all joints and seams taped and waterproofed with liquid waterproofing membrane. Then the tile.

If a tighter radius is required the HardiBacker can be kerfed on the backside the same as Square Eye is suggesting for the plywood bend. Kerfs 1/4" deep and one inch apart should do the trick.


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## J Hawkes (Jan 5, 2007)

Thank you Bud, I am using that Hardibacker board for everything else the tile will cover.  I've only cut through a couple pieces so far in my project.  It seemed so hard and brittle I didn't think it would bend.  When I asked around with the people I knew they said that plywood would work as a base, if sealed properly like you described.  But I want to do it right the first time, so I will try the Hardibacker board. 
Thanks for the advice, I appreciate it.


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## Bud Cline (Jan 5, 2007)

Of all the cement board type tilebackers on the market Hardibacker is the toughest.  Hardi has the highest compressive strength and the highest flexural strength so it won't bend very easily.  This is why you probably have to kerf the backside and that should do the trick.  You may have to experiment a little.  Keep in mind that Hardi is very rigid so it will probably break easily after kerfed, it is important that the kerfs be consistant in seperation and depth.

Also, don't breathe that dust as this will be a very dusty operation kerfing with a saw.  Use a face mask and eye protection and if indoors be sure to ventilate the area well.


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