# Mortar type question S and N? under ground/not under ground



## gball (Jun 24, 2008)

i get the basic idea of the different types of mortar, M,S,N,K,O... but what is it that makes type S ok for under ground block and not type N? 
reason for asking is i am starting a project that will have 8x8x16 block at basement level rising above grade by two coarses. it is an attached garage with a fruit cellar under part of it. after doing the math on how many pre mixed bags i would need i decided to have a friend with a dump trailer bring me mason sand and buy Masonry cement. with out knowing the differences in the types until about a half hour ago... i bought 7 bags of 70# Quikrete Type N masonry cement at home depot. i got a deal on it because all 7 bags on the pallet had (small) tears in them. so i guess what i am wanting to know is am i loading these bags back up and making the 60 mile round trip to return the type N, or can i do the math to add portland cement to the mix to get the same ratio as type S? if it helps with some advice, i am in northern Michigan, so snow could start flying any day but it was in the upper 60's today. and i do have a cement mixer.


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## dakzaag (Jan 6, 2009)

Welcome to CT, post an intro when you get a chance.

Is 4 years between join date and first post a new record?

The differemce is one shovel of OPC (ordinary Portland Cement) which you can add when you mix it, if you so desire. For what it is worth, 7 bags will lay about 280 block, more if you are carefull and less if you experience any issues.

Frankly, you are splitting hairs at this point. With your obvious lack of experience dealing with masonry, it seems to me that the least of your problems is a shovel full of OPC. I rarely use type S, but your location in northern Michigan might be enough of a reason to add the Portland.

If you haven't considered truss wire, cell grout and rebar reinforcement, that extra 7 pounds of Portland is not going to make much difference in the long term performance of your basement. 

So on another note, did you save enough money on 7 bags of Masonry Cement (damaged at that...) to pay for the 60 mile trip, or is that the closest supplier available?


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## woodmagman (Feb 17, 2007)

S, at or below grade for exterior work, N above grade on exterior or interior work.


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## gball (Jun 24, 2008)

*re*

dakzaag, it is actually over 60 miles, but yes that is the closest town to us that we can "shop". We don't have a macdonalds, walmart, and target on every corner here. In fact, there isn't a single regular red, green, yellow street light in our whole county. tractors and deer are usually the only hold up on the road.

well, i will admit this is the first time i have attempted to lay block like this. i have laid a good amount of dry block walls and pavers but nothing with mortar. but like every other thing i can do, some of them pretty well, at one time i never did it before... i did plan for rebar with filled cores. i set the rebar vertical out of the footing enough to place 3 1/2 coarses then will over lap it to extend to top coarse.

so the amount of portland is the only difference then? has nothing to do with any other additives?


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## Tscarborough (Feb 25, 2006)

In addition to adding portland, you can also decrease the amount of sand used per bag for the same effect. For masonry cement (not a PCL mix) the difference is 5 more pounds of masonry cement in the bag:


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## gball (Jun 24, 2008)

Nice, called Quikrete and the tech said NOT to mix anything to it and NOT to use it for my job. Called every building supply and concrete place around and none of them have a Type S masonry cement. They have the S in the premix and they have type M cement, but no S.


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## dom-mas (Nov 26, 2011)

The tech can go suck a lemon. 

Although everyone uses type S for below grade it should actually be a type M below grade. Type S is structural above grade, type M is structural below grade.

Back to the point, the tech can suck a lemon. When you do your mix, whatever amount of type S you use add another 1/4 portland and however much sand you need to bring it up to a 1:3 ratio.

example-15 units of sand: 4 units of type S: 1 unit of Portland.


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## Tscarborough (Feb 25, 2006)

The tech has his head up his ass, or maybe you didn't ask the right questions. Call him back and ask if it is a PCL or MC mix. If it is PCL you can add Portland, if it is MC you can subract sand.

S and N are strength designations, 1800PSI and 750PSI respectively. There many diffenrt methods to achieve those strengths.


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## gball (Jun 24, 2008)

I am going to have to call Quikrete back another day. I just called them again and got the same guy and he had no more of a clue if their product is a PCL or MC mix as i do... i did a search and couldn't find what the difference is either. Are these abbreviations for the contents of the mix? can't believe this project is being held up by something so stupid. hate to return it all but at this point i am thinking about just getting the type M that is available.


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## Tscarborough (Feb 25, 2006)

Sorry, Portland Cement/Lime or Masonry Cement. Bagged masonry cement can be either


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## dakzaag (Jan 6, 2009)

GHall,
Just so you realize, you are splitting a really fine hair here. With rebar and grout fill, your wall will have plenty of strength to withstand pressure from frost heave and moisture. Concentrate on laying up a good plumb wall and give water a place to go below the top of your footer. 
Type N or type S will not be the difference in success or failure here. How often you grout cells and giving water a place to go are far more important. Type N gets used all the time below grade. (not because it is a good idea, but because a lot of builders are ignorant.) I would not hesitate for three seconds to lay up my own basement with Type N. I do specify Type S when asked, but a lot of my customers don't ask.

Masonry is measured for compressive strength, it shines brightest when dispersing weight across a broad section of the footer. The weakness of Masonry is lateral loads that break the mortar joints and structural units. Grout and rebar are specified to beef up the lateral strength. Type S over Type N will not significantly improve lateral strength.


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## jomama (Oct 25, 2008)

dom-mas said:


> The tech can go suck a lemon.
> 
> *Although everyone uses type S for below grade it should actually be a type M below grade. Type S is structural above grade, type M is structural below grade.*
> 
> ...


Around here, it's always been Type M below grade structural, and our code requires it. I can't think of a good reason not to use Type M, other than in the OP's case. As Tscar said, find out if it's a straight Portland/Lime mix (I'm guessing not, but you never know who bags the Quikrete where you're at) or a "masonry cement", and alter from there........


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## 91782 (Sep 6, 2012)

http://www.cement.org/masonry/cc_mortar_types.asp


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## dakzaag (Jan 6, 2009)

SmallTownGuy said:


> http://www.cement.org/masonry/cc_mortar_types.asp


Very nice link. I have book marked that for myself. I found this sentence in the last paragraph to be the most reassuring.

"Rule of Thumb: Use a Type N mortar for all masonry work unless there is a compelling reason to choose another mortar."

:thumbsup::thumbsup:


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## Tom M (Jan 3, 2007)

dakzaag said:


> "Rule of Thumb: Use a Type N mortar for all masonry work unless there is a compelling reason to choose another mortar."
> 
> :thumbsup::thumbsup:


I would say the vast majority of mortar used here is S. Its more of a multi use material.
Im not a mason but from my knowledge the additional lime mixture in the N makes it more flexable and better material for veneers that get lots of forces.
The S can handle more weight from above and cure dense enough to be used below grade. It will still have shrinkage cracks but not as much as M so its less prone to water leakage.


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## concretemasonry (Dec 1, 2006)

Just to confuse matters at bit - There are 3 (not 2) types of cement used for mortars. They are Portland Cement, Mortar Cement and Masonry Cement. All are manufactured by cement companies and some also bag the cements. They can also be sold to commercial bagging companies that supply it in different bags under the three types listed.

Under the proportioning provision of ASTM C270, they can be used in different amounts and proportions with and without lime to create almost every type of mortar by anyone concerned with requiring a certain type of mortar. This is under the proportion mix designs that control the materials. In all cases, the sand volume used must be between 2-1/4 and 3-1/2 times the weight of the cementitious (cement and lime), depending the local aggregate shapes and sizes or the desired workability. Not the this is a proportion specification and not the other type of specification, which is a performance specification that requires different measurements and results, one of which is the compressive strength. You cannot mix the two different specifications because of the possibility of confusion in reporting and complying.

If you look at the Appendix of the the mortar specification (ASTM 270), you will find a recommendation to use the weakest mortar necessary to carry the loads, The table in the proceeding post by SmallTown was taken from the ASTM C270 Appendix also.

Like all ASTM specifications and standards, they have been developed through the years by a balanced consensus group of designers (architects, engineers), users (contractors, retailers, suppliers) and interested parties (little old ladies, groups, code bodies and inspectors).


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