[Cob] lime mortar

[phil]

My understanding of stone walls is that if you are depending on the mortar to make it stand then the wall is likely built with limited craftsmanship. Mortar in a stone wall is there to provide a limited mechanical bond between stones. The real strength of the wall is in the method of construction, i.e. the stones need to fit together and the base of the wall should be wider than the top. I have built with a lime mortar, it works, but I concentrated on a good dry stack method for the wall and only used the mortar to stop air leaks.


Phil

-----Original Message-----
From: "Bob Smolen" [boka at mwt.net]
Date: 01/10/2009 01:18 AM
To: coblist at deatech.com
Subject: Re: [Cob] lime mortar

Last fall, I started gathering old foundation rocks for my cob project. At two sites,only the 8ft stone stem wall was standing where a barn once stood. It was probably 110 years or older. I was able to knock down the wall by pushing on a leaning section. I did not really look at the foundation but the owners commented that the wall came down easy because of the mortar used in the old days. I believe he said it lacked cement which means it must have been lime mortar. Is this an indictment of a non cement mortar? I know the wall was subjected to years of weather unprotected so  maybe deterioration should be expected. On the other hand, I dont think the weather would have affected cement mortar. ( I did not notice the foundation wall. It may have heaved after the roof of the barn was off allowing moisture under the footer causing frost heave).
Is lime mortar as good or close to as good as cement mortar for buiding stone walls?
Thanks,
Bob
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