We had our slate roof re-membraned and re-slated (with new slates) Nov09. Since then we have had to have the roofer back about six times to repair a total of about ten slipped slates. After the latest cold spell last week I noticed two more have slipped and one has cracked in half. I will call the roofer tomorrow.
The roofer seems as disappointed as I am when I ring him up and he turns up resonably promptly to replace the damaged tiles. He questioned the supplier the last time who told him that it is because the roof is south facing!!!
I'm at the point now where I have no faith in the quality of the materials used. Does anyone have a suggestion as to my next course of action or has anyone experienced this problem themselves. I have emailed the NFRC but since the roofer was not a member I doubt there is little they can do.
If the slates were new and they are fixed according to good roofing practice there is no reason why any should slip.
You are just going to have to keep getting the roofer back, you are lucky he is prepared to keep returning.
You should not be loosing slates like this if the roof has been fitted correctly and / or the slates are of acceptable quality.
A slate roof fitted correctly should be able to withstand severe weather conditions with no problem, much more so than concrete tiles for instance.
If you are still having problems I am an independent Roofing Consultant specialising in Slate Roofs and Lead work and would be pleased to advise further if necessary.