# groin vault ceiling



## master mason (Feb 9, 2008)

any feedback on the pros and cons of using thinset or pl400 construction adheasive for installing thinbrick on 3/4" bc grade plywood groin vault ceiling? LMK


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## Bill_Vincent (Apr 6, 2005)

I wouldn't set tile with PL 400, Liquid Nailz, or ANY construction adhesive if you paid me. However, before I tell you what thinset, let me ask you-- what's the species of wood in the plywood?


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## master mason (Feb 9, 2008)

have'nt baught it yet Bill but it will be a nicer bc grade. and it is not tile, it is actually 1/2" thick actual clay red brick


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## Bill_Vincent (Apr 6, 2005)

There's a couple of different ways to go at this, depending on how much room you have to play with. Here's the thing-- the thinset I'd normally recommend for going over plywood (which SHOULD be either fir or spruce, and preferrably fir-- definitely NOT pine!) is one of the following, depending on which is available to you-- Mapei's Kerabond thinset and their Keralastic additive, Laticrete's 317 thinset mixed with their 333 additive, or Hydroment's Tilemate mixed with their Flexalastic additive. It needs to be an unmodified thinset mixed with a liquid latex additive full strength for the extra latex content. Normally. But now we're talking about hanging the tile on a ceiling, and one of the ways the added latex strengthens the thinset is by slowing down the drying and curing process, and that's the LAST thing you want for a ceiling. That said, if it were me, I'd install the plywood, and leave about 1/8" gaps between the sheets. Once installed, use any cheap crap caulking, so long as it stays pliable, and fill those joints. The point of it is to keep the thinset out of those joints so the plywood has room to "breathe" with the seasons. Once that's accomplished, use an alkali resistant self sticking tape, and tape the joints, and then coat every bit of plywood that's going to get the brick with one of the aforementioned thinsets. You want a nice even skimcoat-- this is basically going to act as a bond coat for the thinset you use to install the brick, as well as embedding the mesh tape. Once you've got all this done, I'd go to one of the lightweight nonsag thinsets to actually set the brick with. It'll adhere nicely to the other thinset, and the other thinset will have enough give in it due to the added latex content to take up the expansion and contraction of the plywood. As for the nonsags, there's three That I'm aware of-- Custom's Megalite, Mapei's Ultralite, and Laticrete's 255, the Laticrete being my favorite. Mix this stuff up stiffer than normal thinsets and that brick won't go anywhere.

The other way to go would be to lath the plywood, do a scratch coat, and then any thinset will really do. Like I said, it depends on how much room you have.


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## neolitic (Apr 20, 2006)

Bill,
How would you feel about a 5 ply
Baltic birch for something like this?


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## Bill_Vincent (Apr 6, 2005)

I know some tile guys will go over birch, but I'm pretty much a stickler for using fir or spruce, and I'll only use spruce if I can't get my hands on fir.


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## neolitic (Apr 20, 2006)

MHO fir and birch are equally stable.
Everything else is a distant 4th place.


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## Bud Cline (Feb 12, 2006)

Last recommendations I saw from a thin brick maker was construction adhesive and no specific plywood species was mentioned or excluded.:whistling

Those brick guys obviously aren't as persnickedy as us tile guys are.:notworthy


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## master mason (Feb 9, 2008)

thanks guys, hey Bill I don't want to add any additional weight to the ceiling. That's why I don't want to do metal lathe and a scratch coat.


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## Bill_Vincent (Apr 6, 2005)

If that's the case, I'd go through the rest of what I suggested. Seems like alot, but that installation won't go anywhere.


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## TOthe16th (Mar 4, 2008)

Bud Cline said:


> Last recommendations I saw from a thin brick maker was construction adhesive and no specific plywood species was mentioned or excluded.:whistling
> 
> Those brick guys obviously aren't as persnickedy as us tile guys are.:notworthy


The brick "makers" dont know anything about the nature of the trade. They know how to manufacture material. Us brick guys are every bit as "persnickedy" as you tile guys. An asthetic trade is an asthetic trade.


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## Bill_Vincent (Apr 6, 2005)

Bud, ya GOT one!! Set the hook!!


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## master mason (Feb 9, 2008)

Bill_Vincent said:


> If that's the case, I'd go through the rest of what I suggested. Seems like alot, but that installation won't go anywhere.


Hey Bill you win , I went with the lath,Mapei planitop 12 for the scratch coats,and set the thin brick with Mapei ultra lite thinset. It worked well THX.:clap:


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## Bill_Vincent (Apr 6, 2005)

Good deal. But you know what they say-- a PICTURE is worth a thousand words!! :thumbup:


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## master mason (Feb 9, 2008)

Bill_Vincent said:


> Good deal. But you know what they say-- a PICTURE is worth a thousand words!! :thumbup:


Bill go to the masonry section I have some pictures posted under "groin vault pictures" .I had to get tscarborough to post them through his e-mail, I am still having trouble posting pictures. LMK what you think.


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