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Derkp 04-16-2010 08:27 PM

Type S Mortar + Fireclay = good mix?
Is it possible to use type S mortar + fireclay to achieve a good home brew mortar? Or are the ratios all messed up?

It would be easier to buy the premix and add fireclay rather than buy a bag of lime and a bag of sand and a bag of portland cement and mix them with the clay. Saving a step or two.

Does this make sense or am I up in the night?



Tscarborough 04-16-2010 09:42 PM

Re: Type S Mortar + Fireclay = good mix?
The sand in pre-mixed mortar is not exactly the correct sand, but it is probably close enough. You will have problems getting joints smaller than 1/4" though.

fxpose 04-16-2010 10:04 PM

Re: Type S Mortar + Fireclay = good mix?
Exactly what I needed to know....about the sand. I posted a similar question earlier today and one poster recomended silica sand.

Tscarborough 04-17-2010 06:41 AM

Re: Type S Mortar + Fireclay = good mix?
Sugar sand, pool filter sand, ash tray sand. It is called a lot of things, the most important thing is that it is finely graded.

eprante 04-17-2010 07:38 AM

Re: Type S Mortar + Fireclay = good mix?
while we have you answering mortar questions: I have seen type s mortar and type n, what is the difference?

GianniFocaccia 04-17-2010 07:39 AM

Re: Type S Mortar + Fireclay = good mix?

Here's TScarborough's earlier reply to my question regarding silica sand:

"The rule of thumb is to use as large a sand grain as the joint will allow. So for 1/16" joints, you have the correct sand. For 3/8" joints it is too fine. Even more important than the size is the grading. You want from just above dust to the largest size (1/8" for normal masonry sand), as the cause of the cracking is shrinkage of the cementious paste as it dries. The more the gaps of the mortar are filled with aggregate, the less cracking.

Think of a jar of marbles. The spaces around the marbles are large. Now add in some marbles 1/2 the size, and 1/4 the size, 1/8, etc. The spaces will be much smaller (and uniform) with the blend.

That is what you are trying to achieve with a good mortar or stucco, no matter what it is used for: a blend of aggregate particles coated with a cementious paste."


Tscarborough 04-17-2010 08:22 AM

Re: Type S Mortar + Fireclay = good mix?
Type S and N are STRENGTH designations, not ingredient designations. In other words, a bag of Type N masonry cement will weigh 70#, while a bag of Type S masonry cement will weigh 75# of the exact same material. When mixed with an equal amount of sand, the Type N will produce a mortar with a strength of 750 PSI and Type S a strength of 1800 PSI (There are 2 other Types, O (350PSI), and M (3500PSI).

However it is important to remember that high PSI is NOT the important factor in mortar. Normally the weakest mortar that will suffice is specified. The important physical properties are bond strength and flexural strength, which as a rule are inverse to compressive strength.

Mortar is NOT concrete!

Tscarborough 04-17-2010 08:28 AM

Re: Type S Mortar + Fireclay = good mix?
And just to confuse you further, the Type designation of Portland Cement IS an ingredient designation. Type I or Type I/II are the only ones used in masonry in general.

BTW, here is how they came up with the mortar strength letters:


I dunno why they didn't use "A"

fxpose 04-17-2010 09:20 AM

Re: Type S Mortar + Fireclay = good mix?
Thanks guys, for the valuable info!!

So basically, I will be mixing 2 diff batches of fireclay mortar, one for thin joints and another for thicker joints.

Then, can I use thinset mortar + fireclay in this case, for thinner joints?

egalecki 04-17-2010 10:07 AM

Re: Type S Mortar + Fireclay = good mix?
I used a combination of heatstop and home brew mortar- once I had cut enough bricks to get enough fireclay to use, I had just about run out of the heatstop. Great timing for once...

My sand was basically bagged playsand that I had left over from the plasterers. It was pretty fine stuff. It's really not hard at all to measure the lime, portland, sand and fireclay- I used a plastic cup to measure. That way I never had more made up than I could manage, and the ingredients stayed in the shed just fine. I do still have some lime left, but all the other ingredients got used up.

I don't know if using type S with fireclay is really going to get you what you want- I don't know the ratio of the ingredients in type S, though. I used type S to do my stucco, though, and the sand in it was a whole lot bigger than what I used in my homebrew mortar.

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