Fig. 1 - Cement Pointing - Porous Stonework


5 2


1 3


4 6


1. Cementitious pointing medium in joints of porous stone. 2. Arrows indicate external rainfall and passage of moisture into and down through fissures in the stone toward the pointing joint.


3. Indicates build up of moisture and crystallisation of salts at the position where moisture penetrates to the cement joint.


4. Arrow indicates direction of moisture toward lime masonry bedding joint. 5. Due to entrapment by cement. This will lead to salts and dampness on the internal plaster face (6).


Eventual detachment of cement joint due to weakening of the stone by salts. Damage is likely as cement breaks away due to the freeze/thaw action taking segments of existing stone with it, particularly if the cement matter was originally harder than the stone.


Fig. 2 - Hydraulic Lime Pointing - Porous Stonework FIg. 1. 2


3 1


1. Hydraulic Lime Mortar joint. 2. Arrows as previous. 3. Arrows indicated movement of vapour into and out of the hydraulic lime joint ensuring stabilisation, drying out and no salts to build up. Saturation of existing lime joint does not occur. Hydraulic lime never becomes harder than the stone. Mineral bond between the hydraulic lime and the stone and the hydraulic lime and original masonry bed is assured.


FIg. 2.


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