# Repointing deep foundation joints in 170 year old house



## hdavis (Feb 14, 2012)

FWIW, a lot of lime around here 200 years ago or so was produced locally from oyster and clam shells.


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## hdavis (Feb 14, 2012)

A short article on shell middens up here, they were used for producing lime.

https://mobile.nytimes.com/2017/10/19/science/native-americans-shell-middens-maine.html


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## fjn (Aug 17, 2011)

hdavis said:


> A short article on shell middens up here, they were used for producing lime.
> 
> https://mobile.nytimes.com/2017/10/19/science/native-americans-shell-middens-maine.html




Absolutely.:thumbsup: All along the Eastern sea board shells were used for lime,especially very early in it's settlement,before limestone deposits were discovered and tapped. Colonial Williamsburg still does a lime burn with shells for demonstration purposes.I think they have a youtube video showing the firing.


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## JBM (Mar 31, 2011)

Fouthgeneration said:


> JBM: As water evaporates, the 'S' lime based mortar gets 'harder" and in the confined masonry spaces of bed and head joints can withstand hundreds of PSI of compression for hundreds of years, if the lime isn't washed out over time......


The trade schools use S lime in their teachings of masonry. When they are done building their "thing", they disassemble and put the "mortar" into a wheelbarrow and re temp it for the next lesson. 

It isnt a proper cement.


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## Tinstaafl (Jan 6, 2008)

JBM said:


> It isnt a proper cement.


Diving way over my head here, isn't there a difference between mortar and cement?

Shutting up now...


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## JBM (Mar 31, 2011)

Tinstaafl said:


> Diving way over my head here, isn't there a difference between mortar and cement?
> 
> Shutting up now...


Well ya, cement is slang, can meat concreat or mortar.


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## superseal (Feb 4, 2009)

JBM said:


> The trade schools use S lime in their teachings of masonry. When they are done building their "thing", they disassemble and put the "mortar" into a wheelbarrow and re temp it for the next lesson.
> 
> It isnt a proper cement.


Your forgetting sieving...Our mix was 4/1 and it hardened just fine, surely enough to stand forever without the weather element in play.

We had a huge sieve on sliding casters, about shoulder high...two man operation, back and forth. What broke up simply fell into the bulk mix pile, the rest was ground to a powder using brick. Our mixer was located opposite of the bulk bin so whoever was on mixing duty that day...usually first year students, would simply shovel the bulk mix into the mixer. Chit, we even had a large overhead dust control system in place to keep the clouds down. 

I can still hear good old Franco Nardone, our teacher yelling "don't hit the level" :laughing: As soon as he stepped foot out of class, the mortar fights would begin. Let me tell you something...getting hit in the head with a bed joint of hardened mortar hurts like hell


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## stuart45 (Oct 7, 2009)

Tinstaafl said:


> Diving way over my head here, isn't there a difference between mortar and cement?
> 
> Shutting up now...


Cement is really just a binder which holds the aggregate, such as sand, together. 
Nowadays most people mean Portland cement when then say cement as this is the most common binder, but there are other types. 
Mortar is a comination of an aggregate such as sand and a binder such as portland cement or Lime.


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## hdavis (Feb 14, 2012)

It's funny how excited I can get about a topic like this, and I'm not even a mason.:thumbsup:


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## fjn (Aug 17, 2011)

hdavis said:


> It's funny how excited I can get about a topic like this, and I'm not even a mason.:thumbsup:





That's 'cause masonry is an exciting topic .:clap:


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## JBM (Mar 31, 2011)

fjn said:


> That's 'cause masonry is an exciting topic .:clap:


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## rdrr (Jan 13, 2018)

Thanks for all of the advise you guys have given me, it's been very helpful. I found that I can clean out the joints fairly easily with a vacuum and some improvised tools for reaching further back into the joints. I have found that there is really nothing left in the joints and I can clean out all the way to the back of the stones and the soil for the most part, ~24" inches deep. 

I'm not going to really start in earnest until the ground around the foundation begins to thaw around April or so but I have a couple of additional questions as I get prepared. 
Should the joints be filled in multiple passes or can they be filled all at once? So, should I fill the back of the joint , let it dry, then come back fill it in some more, let it dry ... or fill it in back to front all the way? 

Also, when I was testing cleaning out some of the joints I noticed that there are some larger voids in some of the joints, well big enough for my hand to fit into and move around. Some of them look as if there were some larger filler stones in the back that simply fell out of place without anything to hold them up and some just look empty as if they were only filled with mortar. Are these larger voids ok to fill with just mortar, would adding some stones to fill the gap be ok? 

Thanks again for all the adise


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## fjn (Aug 17, 2011)

A great book that would be helpful too you is The Art of the Stonemason by Ian Cramb. His book is about coursed rubble stone. To answer your question,the mortar should be placed in lifts and compacted when it becomes thumb print hard.Ian shows and explains the tamper he uses to compact the mortar.Also,for large voids,yes add small stones to reduce the need for huge volumes of mortar,it will reduce the mortar shrinkage.


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