A recent grade 2 listed barn conversion complex where a the Collyweston slate was renovated 3 years prior by the sub-contract for the property developers. We were asked by the property developer to do a report on the condition of this re-slated roof because the new property owners were complaining of lumps of mortar from the roof landing in their courtyards and frontage, some of which were rather big and potentially dangerous.
When carrying out the roof survey we were shocked on the very poor condition of the roof and the amount of lime mortar slate beds that had cracked and fallen out. We removed some slates to observe the mechanics of the roof and found that the slates had little or no band, as well as not being drilled and nailed into the slate battens.
On the internal roof void it was clear to see that the secondary white breathable membrane had streaks of black mould, indicating that the roof surface was not keeping the rain water out leaving this roof with a short life span before the membrane begins to rot.
There was no alternative but to re-slate properly necessitating additional expense for the property developer. This highlights the need to use Collyweston trained experts whn handling this type of renovation.