by neil-the-handyman »
Thu Oct 13, 2016 1:00 am
Hi Neil the Oxford handyman here.
If the damp is a relatively new situation that has recently made an appearance then it may be one of the following.
Has the repointing been done using lime in the mix? If it hasn't then what happens is the moisture in the traditional lime mortar behind the new pointing becomes trapped and as it can't 'breathe' externally is forced internally.
An added problem this creates is to create different rates of expansion which will over time cause the snots to snap on the lime plaster and thus crumble.
A bigger problem though is caused externally. If the mortar is harder than the natural granite then moisture is forced into it. When winter comes and it freezes it will blow the faces off the traditional stonework.
Or it maybe that you have new windows and have reduced airflow, if this is the case install vents.
Hope this helps,
Kind regards,
Neil