How to install cultured stone over "scratch" coat?
Question:I have a "scratch" coat of mortor over lath that has dried and want to install cultured "fake" stone to it. I tried to put another layer of mortor on the wall and then some on the stone but I can't get it to stick. What am I doing wrong?
Answers:
interior? use a tile mastic, back butter the stone only. if you are going to have grout joints just go back and fill them with a grout bag and some mortar. (if your staying with the mortar it's all about the mix. also try back butter only. (20 oz pop bottle with a hole in the center for water control add a small amount if you need more stick.)
you're as bad as me, that mortar stuff is tricky stuff. someone will come along soon and give you the right chemistry, but for now you & I are stuck doing the same thing. I'm alaround construction, but I could never get the knack of the mortar, glue and butter it all up and make it stick on a vertical wall, but i have those maxi-friends of mine that work from sunup to sundown and never tire and get it all done like they knew what they were doing. some day I'll get it. I just write the checks.
like bikenut said, it's all about the mortar mix. Mix the mortar fairly wet and add a concrete bonding agent to the mix. Back butter (which means coat the back of the stone rather than coating the wall) with lots of mortar and push the stone onto the wall. Use spacers to keep the stone from slipping or drooping. You can't do all kinds of stone on top of each other at once as the mortar can't set and the stone will fall off.
I assume you have portland cement scratch coat rather than masonry mortar. The manufacturers instructions are the best source for exactly how to apply products. Here is my recommendation to you without knowing how thick, dense and absorbent your material is or whether it is inside or out or whether you are expecting a joint or not.
- If you cannot work quickly as is the case form most doing this work for the first time, wet the surface of the scratch coat with a little water, this give you a little more time to adjust things and slows the setting of the mortar.
-Apply three fourths inch thick masonry mortar using type 1 cement mixed to the directions on the package, do not use mortar that has substantially set up or mix water in the mortar to soften (termed tempering) it more than once as this weakens the bond and ultimate strength of the mortar. Mortar should have a sticky, pliable consistency and should be fresh when applying stone
-To apply the mortar, about three quarters of an inch thick, I use a square concrete finishing trowel to spead mortar, push the mortar onto the wall with the trowel. Apply the stone to plastic mortar getting it to squeeze out all around the stone.
-Use a striking tool to bond the mortar to the stone and the scratch coat by striking, pushing the striking tool against the surface, the whole exposed surface of the joints, the space between the stone. This improves the bond and prepares the mortar to resist weather.
-If you still have problems with adhesion, "back butter" the stones by covering the back with mortar with a masons trowel before placing it on the wall
This advice is just a skeleton of what you really need to know to do this large and complex project. I recommend that you get a book on the subject and read it as well as following the manufacturer's recommendations. This is hard work, slow, difficult if more than a few feet high, and, if it's outside, when it's done wrong can cause substantial problems, as in stones falling from the surface well after the job is finished, and expensive fixes.
I guess experience is a "relative" word to some.
the explanation above me is completely wrong in every way listen to it and you will have failure.
1.All cultured stone is made to "back butter" only.
2. DO NOT APPLY anything to the wall directly as the stone will just fall off or it will dry out.
3.DO NOT WET the wall before applying the stone or it will fall off.
4. DO NOT WET the stone or it will fall off
5. Get a bag of dry premixed masons mix at H.D. or Lowe's
6. Get a bag of straight Portland cement ad H.D. or Lowe's
7. Before mixing the masons mix add about 2 shovels of Portland cement to it, mix it up dry and then add water and mix till it is moist but not wet. (keep it on the dry side for now) after it sets a few min you can see if you need to add more water.
8.Using a masons trowel or depending on your skill level and stone size you can use a "margin" trowel.
9.While holding the stone in one hand with the other hand place the mortar all the way around the stones edges..this is kinda hard to explain but kinda like you would wipe the excess mayo off a butter knife back onto the container (at an angle) you should have a "ring" of mortar that is about only 1" thick any thicker and it will fall off.
10. with the mortar all the way around you can put some in the center if they are large stones if not just keep it on the edges.
11. Immediately press the stone to the wall and wiggle it around very slightly to put in in position (not much I'm talking only very slightly) hold it there for a count of 5 or 6 and let go. LISTEN UP if the mix is at the right moisture the stone will immediately stick to the wall. the reason being the dry "scratch coat" will suck the moisture from the back butter and you will have a instant bond.
12. repeat this process for adhesion of remaining stones. post again with question about filling the joints and mention the manufacture and the name of the stone. it will help
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