How can you tell the difference between lime mortar and cement mortar?

If you own older heritage property built before about 1920 with solid walls then you really need to understand the difference between lime mortar and cement mortar. Solid walls manage dampness very differently to more modern cement/brick cavity walls and using modern materials on older buildings can cause serious long term damage. 

Visually it is sometimes possible to tell the difference between lime and cement based render of pointing. Lime tends to have a creamy and milky appearance whereas cement based mortars will often be a shade of grey. I have heard that lime can be very white, although, this is not my experience so perhaps this is more prevalent in other parts of the country. 

The fastest way to tell the difference between lime mortar and cement mortar is to use vinegar to cause a reaction. The short clip below will show exactly how to do this. Note that crushing the sample helps the reaction and simply squirting vinegar on the wall doesn’t work well.  


While this technique will tell you if you have lime or not be aware that it cannot tell you anything about the exact mix used. If you are considering a large renovation project then it is well worth having a sample analysed by some like Mike Wye Associates. 

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