Making Mortar More Sticky

mcgyverdc

Working on my 2' high retaing CMU wall and facing with river rock(aprox 8"x8"x4") problem I'm having is my mix of 1:3 portalnd type S and sand isn't very "sticky". I'm wetting the stones and CMU with a spray bottle but having a hard time "buttering" the backs of the stones. I've thought about lime but what proportion. thanks

Teetorbilt

When I get to Heaven, Dad's going to thump me for not knowing the answer to this. Don't take my word on it, but I believe that you add sodium silicate. I never really cared for masonry. I'm a woodworker.

Let's see.

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denick

MC,
If your using 94# bags of portland cement, you can add 1/2 to 1, 50 lb bag of masonry lime. Remember you want the cmu damp but not wet. You don't want things to slide off. You can paint the back of each rock with just portland cement that you add water to and make it the consistancy of a thick paint.

There is a post here that goes into a lot about mortars. Tscar is quite the student of mortar designs.

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Nick

"Every day I remind myself that my inner and outer life are based on the labors of other men, living and dead, and that I must exert myself in order to give in the same measure as I have received and am still receiving" Albert Einstein

tkle

If it's phoney stone either use a 2.5 to 1 then add thinset to the mix as desired or use spec mix.For real stone use the 2,5 to 1 mix with about a quarter shovel of lime per half bag to stop the water bleeding.Use only enough water to make it workable.Lay the stone up without buttering the backs,then parge the back of the layed stone and wall filling the gap as the morter sets.Don't wet the stone.

mcgyverdc

TKLE...thanks...so just so I have this right..parge the wall where I want the stone (real river rock) press the dry stone into this parging, then push the parging down towards the gap between the cmu and the stone to fill the gap ( i use a pointing tool for this). Didn't think about leaving the rock dry....

stacker

this is what i use when laying artifical stone.
17 full shovels of sand(sq point)10 shovels,then cement,then 7 more
1 sack mason cement
2 shovels portland cement.
stucco the wall in about a 12 sq ft area,push stone into the stucco,after that area is covered,i use a grout bag to fill my joints.then move on down the wall.if i have a problem with the stone sticking,i butter the back of the stone.

with natural stone.i use the same mix,and then spread the wall as if i were laying brick.i try to keep as much cement as possible from behind the stone.this will keep it from pushing the wall out.but there are places where you need to fill in behind to keep the next stone up.just becareful of this.
good luck.

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Tscarborough

Are you using REAL stone that has been sawn thin/fake stone or full size stone? It sounds like you are trying to stick dimensional (8x8x4) stone to a CMU wall, which will not work.

mcgyverdc

Tscarb.....real stone (not cut or flaked)..averages the size I stated with some smaller filler stones...why won't it stick if I fill the gaps later with a grout bag? I am doing this in stages with spacers between the lower rows of stone after they have dried and are solid I figure it will take about 3 sessions to get to the top of the CMU wall. Will be capped to avoid water from entering between the CMU and stone. ie one solid cmu/stone mass So are you saying that eventually the cmu and rock will "delaminate"?

Tscarborough

Well, I guess I have never really thought about it. I can tell you the proper way to do it, though.

Assuming that your footer is big enough to provide a base for the stone, you simply lay the stone as you did the CMU. There should have been ties placed when you laid the CMU, 24" OC horizontaly, 18" vertically (call it 8" for a 24" wall) to tie the CMU and stone together. Assuming you will cap the wall with a unit that spans the CMU and rock, that is pretty much all there is to it.

mcgyverdc

Tscarb, that's exactley as i have done! footer is large enough to support the rock and ties were placed. after the stone is "mounted" to the wall I'll go back with a grout bag and fill in and sculpt my final joints. finally i'll cap it off with 1.5 to 2" sand/type s mix that will completely cover the CMU and rock. i think it will look good...just want to be sure that it will be there in 50 years.....this wall has been backfilled, it was parged before the back fill and drainage is not a problem. thanks

Tscarborough

OK, I guess what I don't understand then is why you would have to go back and tuckpoint the joints. Did you do the same on the CMU?

edit-You do not "mount" the stones to the backup wall, just stack them (lay them in mortar) in front and tie them together as you bring the wall up. You should be able to do the whole veneer at once, and do not need to worry about parging or filling the space between the wythes.

mcgyverdc

Tscarb..the reason is that the rocks that I have picked are not really round. more oblong and thinner ie 8x8x4 or so and I have set them kinda on end so they are only 4 thick from the CMU's. simular to what you would do with fake stone and veneering.

Tscarborough

That is what I am telling you: What you are doing is NOT similar to thin stone or fake stone. Thin/fake stone is ahdered to the backup; it does not need or have a footer to sit upon. The rock you are using is too heavy to adhere to the wall, it has to be supported by a footer, and be laid in mortar, just like a brick or CMU.

1over2

This thread pretty much sums up what cultured stone and lick and stick stone has done to our industry.

mcgyverdc

So concievably if I can get the rock to adhere to the CMU wall by bracing and spacers then go back and fill in between the rock and tuckpoint(tool) it should amount to the same thing, no? Do you foresee any structural problems down the road? the more i think about it....it should work. I'll try to submit a photo down the road before I fill in between the rocks. thanks you given me alot to think about.

Tscarborough

Why are you trying to make it harder than it is? Lay the damn rock like you laid the CMU and be done with it!

stacker

i agree 110%.
i disagree with this statement 110%.
what this thread pretty much sums up,is the effect all those damn dyi tv shows have done to our industry.everyone thinks they can do these jobs,and they are going to do it like the tv show told them too,and when it doesnt work they come on to forums like this and ask for help.which is great,but please listen to us!most of those tv show hosts are just some pretty boy they found at the mall.look at the dumb azz on "this old house",if it wasnt for tom sylva he couldnt build a dog house.

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mcgyverdc

Thanks Stacker....saw one done by a "pro" simular to what i'm doing and was just trying to emulate the look. No wasn't on one of those DIY shows.....arggg the thing that makes this one unique is the tooling that he did on the mortar between the stones kinda a peak in the center that then goes back towards the stone (looks like a little mountain range in the mortar. very cool...didn't think that i could do the tooling and lay the stone all in one shot so i thought if i concentrate on the stone then pipe in the mortar and tool.....will get more of a consistent look. Cheers

1over2

What I meant from my post was that most new stonemasons are being taught on fake stone and thin veneers. A lot of GC's and masons never learn how to properly lay a full bed depth veneer, and when they are faced with a job that requires it they rely on construction methods that are not appropriate. Unfortunatley they also rely on basic square ft estimating.

Tscarborough

You are looking for grapevine or convex jointing, mcgyverdc, and it has nothing to do with how the stone is laid. You can either do that effect as you lay it or rake the joints and tuck it later with a grapevine/convex jointer (recommended method). Either way, you still have to set the stones in a full mortar bed and not try and adhere them to the backup.

Masons around here do not lay "stucco stone", as that is what it is: the third and final coat of a 3 coat cementious stucco system. Fake stone has not hurt the industry a bit; it has, in fact, expanded it.