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I’m looking for a good mortar mixture to use for repointing
a stone chimney.
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Just to get this started...
I'd try 1 shovel Type S, 3 shovels mason's sand, and maybe a quarter shovel Portland for more stickiness. Keep it kinda dry be/c you don't want it slopping around on you and the brick.
*Sand stone and other soft stones use a softer mortar .Like type s. On harder stones ,limestone and granite use portland cement to make a hard mortar
*What is the key to making a very sticky mortar mix? I'm working on installing some cultured stone and having a hard time geting it to stick. Thanks Brent
*For cultured stone I used a recipe recommended by a stucco contractor. Worked like a charm--great suction and great stickiness.3 shovels sand3 shovels type S1 shovel portland1 shovel ABC (Acrylic Base Coat--the base coat used for synthetic stucco)That assumes my memory hasn't faded, so it's always caveat emptor.
*Brent,The way we have done our cultured stone is to mix a bag of Type S mortar and then 3-4 shovel fulls of portland cement. Mix that all together dry and then add water. Our stone has been sticking very well. Hope that helps. We are DIYs who have just kind of worked this out on our cabin, but it seems to work. Obviously, we are doing it on a small scale, so that might not work for you. Good luck. I've never done any project so instantly gratifying as putting up cultured stone. It changed the look of our log cabin completely. Now we are putting it on our shed. We're addicted and we can't stop. :-)
*Do you guys know what the difference is in Type N and Type S? The local Home Depot carries type 1,2 portland cement. Can anybody tell me what the differences are? Thanks in advance for the feedback.
*Type N masonry cement has roughly twice as much lime in it as Type S. The additional lime makes it easier to work, but there is some loss of hardness. Type I portland cement is the "normal" stuff. Type II is used in coastal areas where it might be exposed to sulfates. There's also a Type III for high early strength.
*Try this link . . .http://www.uvm.edu/~histpres/203/mortartable.htmlAn easy way to remember the different types is this;M a S o N w O r K. Capitalized letters are the mortar types from hardest to softest.Hope this helps.Eric
*What creates the sticknes like you get the thin set?
*Eric, what part of the mortar mixture creates sticky ness? I have bought a bunch of Quickcrete Commerical Grade Mortar Mix and can't seem to get it to create a good bond. Any suggestions? Thanks Brent
*It is the portland in the mix that gives the stickiness. Under a microsope, it is like little suction cups. It may be that to save money (like most products sold through HD) Quickcrete uses a slightly lower or a minimum amt of portland in the premixed stuff. Adding too much portland makes the finished product more brittlehard and likely to crack from shrinkage or stress, so be carefull adding it. Lime not only makes the wet mix more workable but creates a slightly flexible, self healing bond joint.The other things causing your problem with stickyness could be letting it stand too long before using or not prewetting the stone. A dry stone will suck the water right out of the mix, creating a fine layer of powder that hinders good bonding. Good technique would be to prewet the stone so it is slightly damp when placing it to the mud on the wall, tapping it a few times to 'walk' the mix into the capillaries of the stone. If in a sunny location, put up a shade clothe to stop the sun from drying it before it can cure and possibly place a dampenned burlap over the space after you've moved on to the next area.Portland products do NOT dry. They CURE by a hydraulic chemical reaction. Allowing the water to leave the mix by drying before the cure happens will weaken the bond and the strenghth
*Brent,If you're looking for a material to bond synthetic stone to a cementitious substrate, mortar may not be the best choice. Due to the low IRA (suction) of most cultured stone, there is no natural draw present to "stick" the two materials together. A thinset type product or mastic would probably serve your purpose better. If you're pointing or laying masonry, you probably don't want a sticky/smeary type of mortar due to the mess you'll create.If, on the other hand, by sticky you mean mortar that stays on the trowel, then that's an easy fix. Mixed mortar should contain as much water as the mix is capable of holding. Retemper in hot, dry weather to maintain plasticity. Dry mortar will not stick to the trowel and will not create watertight joints.I hope this answers your questions. If not email me.Eric
*For what it's worth, the Cultured Stone instructions recommend a Type N mortar. The recipe I was given using Type S gave a GREAT suction if done to a good thickness (3/8", 1/2" or so), proper medium wetness, and without too much wiggling after getting the suction. I coulda stuck these things upside down and not lost any. It also cleaned up real nice as long as you weren't inclined to smear it off before it had a chance to set up for a few hours (but less than a day). Really shouldn't have to go to the extra expense of thinset.I'd also recommend doing your own mix rather than using mix-in-a-bag. A mason I just spoke with said the mixes don't include nearly as much portland as he'd include. Get the ingredients in their separate bags, get a good mason's sand and roll your own until you're happy with the recipe and wetness. I know the consistency I like when I see it, but it's hard to describe. Dryer than pancake batter; wetter than cous-cous; a little wetter than refried beans; maybe like my wife's mashed potatoes. :)Jim
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I'm looking for a good mortar mixture to use for repointing
a stone chimney.