Lime and Earth mortars were replaced by cement in the 20c; this one material has caused so much damage to our old buildings in so many ways. Anybody using cement in an old building doesn’t know what that are doing to it.
Lime is simple to use, with a little understanding
Lime can be categorised into two types:
- Non Hydraulic Limes (putty and quick/hot lime)
- Hydraulic Lime (Natural Hydraulic Lime and natural cements)
The main differences between the two types are:
- Non Hydraulic Limes are pure lime, they set by carbonating and generally have additives mixed in with the mortar mix to gain stronger final sets, theses additives are known as Pozzolans; Pozzolan additives we developed by the Romans.
- Hydraulic Limes set by adding water to them. They have measured percentages of clay added in with the powdered lime. The amount of clay determines their final set strength – (A word of caution- modern NHLs have a far stronger set than historic ones, for instance modern NHL 2 will set stronger than an old moderately hydraulic lime and a modern NHL 3.5 can set as hard as cement). Both types of lime have their place in traditional mortar mixes but careful consideration must be given to which type is used.
During the hundred years between 1750 and 1850 major discoveries were found about mortar properties. The relationship between limestone and clay additives were not understood before John Smeaton’s work in the 1750’s which confirmed the link between the clay content in lime stone and hydraulicity.
The SPAB Technical Pamphlet 5; Repointing Stone and Brick Walling is an excellent guide and only costs £5, it might just be the best money you will ever spend on your old buildings walls. Contact the SPAB and ask them for a copy.
For more in-depth information See the papers prepared by Gerard Lynch and Tim Radcliff:
Also see Mike Wye & and Associates and Abode at Faversham for guidance and practical advice;
TRADITIONAL BUILDING GUIDE SHEETS & VIDEOS
Are you interested in lime and other traditional building materials ?
If you are are a craftsman/woman and you would like know more about how to use traditional building materials, please feel fro to contact us, we would be delighted to help you – and we might even have some work for you ! Interested ?
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