mortar for limestone blocks

[Nick Durnan <durnan@zzzzzzzzzzzzzzz>]

George
The masons I know who work like me on historic buildings prefer to bed
the stone on mortar rather than using spacers as this gives a more even
loading pressure between the blocks. Sometimes there is no option but
to use spacers, when building an arch on wooden centring for instance
to get even joint widths. But that said I have never seen any evidence
of spacers on any mediaeval work I have dismantled, on arches or
anywhere else. As for adhesive properties I feel that mortar is not for
adhering or glueing blocks together but rather as a material for
keeping then slightly apart, for filling joints and providing even
loadings between them.
Our regular mortar is pozzolanic putty lime mortar or slightly
hydraulic lime mortar as we have seen the damage caused by the use of
Portland cement mortars used by the Victorian and 20th century builders
especially for limestone.
Nick

On 6 Dec 2004, at 14:08, George Graham wrote: