I want to just "butter" up some flat pieces of flagstone, the biggest one
square foot. Most less. I want to stick them to a cinderblock wall that I
have powerwashed the paint off. I am also going to make some boxes out of
cinderblock, and cover them with flagstone. I guess the mortar would be
about 1/4" to 3/8" thick. Is that okay? Should I just use premixed mortar
I have hundreds of pounds of flagstone left from laying walkways.
I live in Las Vegas, where it gets hot, is mostly warm all the time, hardly
freezes, doesn't rain very often, if that makes a difference in the mixture.
I want to buy a small mixer, mix as much as I can use in an hour or so, then
mix another exactly like the first. How long until I have to use up the
mortar? Start from the top down on the vertical surfaces so I don't spatter
the previously laid stones?
This will work with premixed mortar and give you a uniform color. You will
need to start at the bottom and support each from the one below. Use broken
pieces for shims. Point the entire wall after all stones are set.
Either or. Latex modified thinset will have the greatest adhesion. If
you want to use mortar, brush some Weldcrete on the back of the stone -
it'll make it stick much better. Skimcoating the wall and buttering
the back of the stone would be a good way to go. Dampen the block
before you start setting and do that periodically in the section you're
moving into. It'll keep the block from sucking the moisture out of the
mortar too quickly and interfering with the curing. Spray the
installation with water periodically during the first three days so the
mortar will achieve its full strength.
The working time is dependent on the temperature and humidity. Since
you're in high temperature low humidity land, it won't be a very long
time. You'll figure it out as you go along. Don't mix up too much to
In any masonry work, you work from the bottom up. You really have to
due to the weight of the materials. Don't worry about the splatter too
much - just have a damp sponge handy.
I used pavers on a block wall and I found out "bonding" mortar mix
does a great job. It has less latex than "flex" so it is cheaper.
"Flex" is really sticky stuff but pricy. Once you get it stuck up
there you can grout it with regular stucco mix, white or grey..
I don't think this is going to work very well. Mortar isn't
glue, and most of the stone veneering products I've seen are
a couple inches thick, which allows for stacking, and better
mechanical locking. I'd expect flagstone to be too thin.
Was I doing this with flagstones less than 1 1/2" thick,
I'd think seriously about using grout-colored epoxy.
Boulder creek has installation instructions for there
"simulated stone" venner product, which I suppose you
could try following, at
But you should note first that the product they're talking
about weighs only about 90 pounds per cubic foot, which
I believe is noticably lighter than most stone.
(see also http://www.halquiststone.com/thinveneer/installation.cfm )
If you use the latex fortified mortar it is. If you spring the extra
$10 a bag for "flex" I am not sure how you would get the stones off
I had to cut some pavers off a wall I set with flex and ended up
chipping them out in pieces and grinding the flex off the wall.
"Bonding" grade is plenty.
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