# Mortar and Portland for stone masonry



## Joel_BC (Nov 10, 2009)

Around where I live, masons working with stones often seem to use a "mortar" mixture of 50% Portland cement and 50% type-S mortar powder. Then they generally mix this mortar 1:3 with clean sand, and of course with water.

I've been using this mixture myself. No complaints, though I feel a bit ignorant. Maybe I haven't met and talked with enough masons.

Anyhow, it's made me wonder... does anyone use pure "masonry mortar", straight from the bag, to mix with sand and water? If so, how does it work out? and are there any advantages or disadvantages to using masonry-mortar alone in such applications?


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## T-Bone 369 (Jan 18, 2007)

For most applications we use mortar mix and sand. The mortar mix is portland and lime so adding more portland changes the ratio of portland to lime. In the old days the portland and lime were seperate and mixed with the sand at the time you made the mortar. Going to the pre-mix made it both simpler to mix and more consistant from batch to batch. One of the disadvantages of masonry cement is that it can shrink when you have large joints - for brick and block it works great but when you get into stone you can get some pretty big joints. Adding extra portland helps prevent shrinkage cracks but the mortar is less "creamy" (that's one of those technical terms we use). It's a trade-off as less creamy mortar is somewhat harder to work with. 

There are different types of masonry mix - N and S are the most common by far. The difference it the amount of portand in the product. Type S has more portland than N and is what we use for concrete block as it makes a stronger mix. Several times we have used other mixes (Type O IIRC) tuckpointing older buildings as it is weaker yet. This is a case where you want a less strong mortar to better match the older existing mortar because if you use N or S you can fracture the face off the work as the building expands and contracts. 

There is also pre-mix with masonry cement and sand but frankly it is pretty poor stuff to use - it is way to lean (too much sand) to be workable. It also is pretty expensive compaired to mixing with S or N. 

I hope that helps.


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## Joel_BC (Nov 10, 2009)

T-Bone 369 said:


> I hope that helps.


T-bone, it helps a lot. Thanks.

With the limited experinece I have, I can still understand the shrinkage issue (for _stone_ masonry) that you carefully explained.

Maybe the higher proportion of portland in the mix also helps with hardness & durability of the joints over time? Speaking of new jointing work, rather than refurbishing of old work. (But just a guess.)


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## rickfrosty (Jun 19, 2008)

Had a mason tender friend get upset w/me for askiing this dumb question, but in stone masonry (not fancy - big stones & small, not fitted carefully at all, so some areas of big joints), can you use a mortar mix more closely resembling concrete ? In other words w/some aggregate in it ? Obviously the larger pieces of aggregate couldn't go in a spot where the big stones would fit closely.


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## JohnnyLee (Feb 13, 2011)

You can use aggregate in the larger areas - for a uniform look, you would have to spread a thin layer of mortar over any exposed aggregate.

Think of mortar just like you would concrete mix, but with smaller aggregate and the additional lime adds plasticity to the mortar, making it easier to more level lines between bricks or blocks.


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## Farmerwilly2 (Oct 14, 2006)

We do our stone work with pee poor mortar with coarse sand. Almost looks like damp sand when you see it. This is much less sticky than a brick or block mix. As my pop and the stone man that showed me explained it, this allowed for more flex in the stonework. I enjoy working our limestone, has a good feel to it and cuts nice.


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